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Host Unit：Nanjing University of Information Science & Technology
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2023,46(4): 481-490, DOI: 10.13878/j.cnki.dqkxxb.20230517001
Abstract:
The investigation of climate change in arid and semiarid regions has long been a prominent scientific issue of extensive interest,particularly concerning the patterns and future trends of dry and wet climatic variations.Previous research has made significant advancements in unraveling the facts and mechanisms underlying these climatic changes across diverse arid and semiarid regions worldwide.Although the 6th IPCC evaluation report indicates a projected exacerbation of global aridity trends in the future,several contentious issues persist.This paper provides a comprehensive review of studies focusing on interdecadal changes in dry and wet conditions,particularly interdecadal drought,in arid and semiarid regions within the context of global warming.The current state of related research is systematically analyzed,and key scientific challenges faced by arid and semiarid region studies are identified.
The investigation of climate change in arid and semiarid regions has long been a prominent scientific issue of extensive interest,particularly concerning the patterns and future trends of dry and wet climatic variations.Previous research has made significant advancements in unraveling the facts and mechanisms underlying these climatic changes across diverse arid and semiarid regions worldwide.Although the 6th IPCC evaluation report indicates a projected exacerbation of global aridity trends in the future,several contentious issues persist.This paper provides a comprehensive review of studies focusing on interdecadal changes in dry and wet conditions,particularly interdecadal drought,in arid and semiarid regions within the context of global warming.The current state of related research is systematically analyzed,and key scientific challenges faced by arid and semiarid region studies are identified.
Natural emissions of short-lived climate forcers and their climate feedbacks:IPCC AR6 interpretation
ZHANG Hua, YANG Zhenjiang, SU Hongjuan, ZHANG Danyuting, AN Qi, YUAN Chang, LI Shuai, HE Jingyi, XIE Bing, ZHAO Shuyun, LI Ke
2023,46(4): 491-498, DOI: 10.13878/j.cnki.dqkxxb.20220921001
Abstract:
Short-lived Climate Forcers (SLCFs) have a significant impact on air pollution and climate change.The Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) pays a special attention on SLCFs,which includes an assessment of natural emissions of SLCFs in addition to the anthropogenic SLCFs.The understanding of natural emissions of SLCFs and their climate feedbacks would be more important in the future with the reduction of anthropogenic SLCFs under climate warming.In this paper,the latest findings from IPCC AR6 are introduced in terms of natural emissions of SLCFs,changes in emissions under historical and future climate scenarios,and their climate feedbacks.Under climate warming,future emissions of lighting NOx,biogenic VOCs,and biomass burning will likely increase,and the sensitivity in emissions of soil NOx,dust,sea salt,and dimethyl sulfide (DMS) to climate change is uncertain.Meanwhile,due to changes in emissions,atmospheric burden,or lifetime of SLCFs in response to climate warming,the overall effect will likely result in a negative feedback of -0.20 W/m2/℃ (-0.41～+0.01 W/m2/℃),which may slightly mitigate climate warming.
Short-lived Climate Forcers (SLCFs) have a significant impact on air pollution and climate change.The Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) pays a special attention on SLCFs,which includes an assessment of natural emissions of SLCFs in addition to the anthropogenic SLCFs.The understanding of natural emissions of SLCFs and their climate feedbacks would be more important in the future with the reduction of anthropogenic SLCFs under climate warming.In this paper,the latest findings from IPCC AR6 are introduced in terms of natural emissions of SLCFs,changes in emissions under historical and future climate scenarios,and their climate feedbacks.Under climate warming,future emissions of lighting NOx,biogenic VOCs,and biomass burning will likely increase,and the sensitivity in emissions of soil NOx,dust,sea salt,and dimethyl sulfide (DMS) to climate change is uncertain.Meanwhile,due to changes in emissions,atmospheric burden,or lifetime of SLCFs in response to climate warming,the overall effect will likely result in a negative feedback of -0.20 W/m2/℃ (-0.41～+0.01 W/m2/℃),which may slightly mitigate climate warming.
LIN Wenqing, CHEN Huopo, XU Huiwen, AI Yawen, HE Wenyue, ZHANG Dawei, WANG Fan, BI Wuxia, WANG Weiqi
2023,46(4): 499-516, DOI: 10.13878/j.cnki.dqkxxb.20221118007
Abstract:
Based on the observation and a set of downscaling bias corrected model (NEX-GDDP-CMIP6) data,this study has investigated the model performance in simulating precipitation extremes over Southwest China using Taylor diagram and GEV fitting methods.Furthermore,the future changes of precipitation extremes that with different return intervals and their associated population exposure are also explored.Results show that NEX-GDDP-CMIP6 models and the multi-model ensemble (N-CMIP6-MME) can reasonably capture the spatial-temporal characteristics of changes in precipitation extremes over Southwest China,and N-CMIP6-MME out performs most of individual models.In the future,the precipitation extremes are expected to significant increases over most regions of Southwest China,including the extreme events that occurring once in 10 or 20 years,which will further increase the risk of population exposure to these extremes.Additionally,for the more extreme events (once in 20-year),the increasing magnitude of its occurring probability would be much greater and it would also exert a larger increase of its associated population exposure,when compared to the events of once in 10-year.Around the year of 2050,the occurring probabilities of the RX1day (RX5day) extremes that occurring once in 20-year are expected to increase by 175.2％(148.9％),216.0％(162.4％),210.9％(156.8％),and 274.3％(207.1％) under SSP1-2.6,SSP2-4.5,SSP3-7.0and SSP5-8.5 scenario,respectively.Correspondingly,thepopulation exposuresare projected to respective increase by 129.1％(118.8％),177.7％ (135.1％),182.4％(143.2％),and 237.5％(161.5％).Further analyses indicate that the increase of population exposure to the precipitation extreme over Southwest China is mainly due to the significant increase of precipitation extremes,and the changes in populations and their interaction generally present a negative contribution.
Based on the observation and a set of downscaling bias corrected model (NEX-GDDP-CMIP6) data,this study has investigated the model performance in simulating precipitation extremes over Southwest China using Taylor diagram and GEV fitting methods.Furthermore,the future changes of precipitation extremes that with different return intervals and their associated population exposure are also explored.Results show that NEX-GDDP-CMIP6 models and the multi-model ensemble (N-CMIP6-MME) can reasonably capture the spatial-temporal characteristics of changes in precipitation extremes over Southwest China,and N-CMIP6-MME out performs most of individual models.In the future,the precipitation extremes are expected to significant increases over most regions of Southwest China,including the extreme events that occurring once in 10 or 20 years,which will further increase the risk of population exposure to these extremes.Additionally,for the more extreme events (once in 20-year),the increasing magnitude of its occurring probability would be much greater and it would also exert a larger increase of its associated population exposure,when compared to the events of once in 10-year.Around the year of 2050,the occurring probabilities of the RX1day (RX5day) extremes that occurring once in 20-year are expected to increase by 175.2％(148.9％),216.0％(162.4％),210.9％(156.8％),and 274.3％(207.1％) under SSP1-2.6,SSP2-4.5,SSP3-7.0and SSP5-8.5 scenario,respectively.Correspondingly,thepopulation exposuresare projected to respective increase by 129.1％(118.8％),177.7％ (135.1％),182.4％(143.2％),and 237.5％(161.5％).Further analyses indicate that the increase of population exposure to the precipitation extreme over Southwest China is mainly due to the significant increase of precipitation extremes,and the changes in populations and their interaction generally present a negative contribution.
2023,46(4): 517-531, DOI: 10.13878/j.cnki.dqkxxb.20220701001
Abstract:
Based on reanalysis datasets of land precipitation,circulation,radiation,and indices representing atmospheric waves,anomalies of the East-Asian circulation and the summer precipitation in North China of the years in which El Niño decayed fast in spring are compared with those of El Niño slow decaying years between 1951—2020;And the reason why El Niño decayed fast in spring in some years was discussed from the perspective of atmospheric wave intensity.Results show that,compared with the other years without El Niño decaying,the precipitation in North China in July and August of the fast decaying years are significantly greater,especially in August.In contrast,the summer precipitation in North China are not significantly greater in the slow decaying years.There was an anomalous anticyclone at 850 hPa over the Philippines to the South China Sea from June to August in the fast decaying years,which was much stronger than that in the slow decaying years.The western Pacific subtropical high (WPSH) at 500 hPa was significantly northward-displaced in August in the fast decaying years,while the WPSH in the slow decaying years was more westward rather than northward.The 200 hPa subtropical westerly jet in August of the fast decaying years was significantly northward,while the corresponding westerly jet in the slow decaying years was slightly southward.And the Walker Circulation from June to August in the fast decaying years was much stronger than that in the slow decaying years.These circulation anomalies in the fast decaying years provided favorable conditions for more precipitation in North China from July to August.According to the composite analysis of near-surface wind,the outbreak of anomalous equatorial easterly wind occurred around the month in which El Niño decayed fast over the Western and Central Pacific.However,in the slow decaying years,the anomalous equatorial easterly wind was much weaker and unsignificant.The convection over the Indian Ocean remained active and spread to the Maritime continent during the fast decay of El Niño.Such continuous active convection very likely induced the outbreak of anomalous near-surface easterly wind by triggering atmospheric waves,and consequently resulted in the fast decay of El Niño.
Based on reanalysis datasets of land precipitation,circulation,radiation,and indices representing atmospheric waves,anomalies of the East-Asian circulation and the summer precipitation in North China of the years in which El Niño decayed fast in spring are compared with those of El Niño slow decaying years between 1951—2020;And the reason why El Niño decayed fast in spring in some years was discussed from the perspective of atmospheric wave intensity.Results show that,compared with the other years without El Niño decaying,the precipitation in North China in July and August of the fast decaying years are significantly greater,especially in August.In contrast,the summer precipitation in North China are not significantly greater in the slow decaying years.There was an anomalous anticyclone at 850 hPa over the Philippines to the South China Sea from June to August in the fast decaying years,which was much stronger than that in the slow decaying years.The western Pacific subtropical high (WPSH) at 500 hPa was significantly northward-displaced in August in the fast decaying years,while the WPSH in the slow decaying years was more westward rather than northward.The 200 hPa subtropical westerly jet in August of the fast decaying years was significantly northward,while the corresponding westerly jet in the slow decaying years was slightly southward.And the Walker Circulation from June to August in the fast decaying years was much stronger than that in the slow decaying years.These circulation anomalies in the fast decaying years provided favorable conditions for more precipitation in North China from July to August.According to the composite analysis of near-surface wind,the outbreak of anomalous equatorial easterly wind occurred around the month in which El Niño decayed fast over the Western and Central Pacific.However,in the slow decaying years,the anomalous equatorial easterly wind was much weaker and unsignificant.The convection over the Indian Ocean remained active and spread to the Maritime continent during the fast decay of El Niño.Such continuous active convection very likely induced the outbreak of anomalous near-surface easterly wind by triggering atmospheric waves,and consequently resulted in the fast decay of El Niño.
2023,46(4): 532-548, DOI: 10.13878/j.cnki.dqkxxb.20221025001
Abstract:
This study investigates the characteristics and underlying processes of the month-to-month reversal of air temperature anomalies in Northeast Asia during early summer (May to June) on the interannual timescales,focusing on the influences of soil moisture anomalies in eastern Europe.Utilizing observational and reanalysis data spanning from 1979 to 2020,the results reveal that the dominant mode of intermonthly variation in air temperature anomalies exhibits a reversal pattern,with warmer (colder) conditions in May and colder (warmer) conditions in June.This reversal mode is directly linked to circulation anomalies over Northeast Asia.Further analysis demonstrates that reduced soil moisture in eastern Europe during May contributes to a warmer May and a colder June in Northeast Asia.The potential physical processes driving these effects are explored.Lower soil moisture in May leads to local soil warming and subsequent warming of the lower troposphere.This,in turn,weakens (enhances) the lower tropospheric meridional temperature gradient and baroclinicity in the Mediterranean region (northern Europe).Consequently,high-frequency transient wave activity weakens (enhances),facilitating the formation of an anomalous high-pressure system over central and eastern Europe,thereby generating Rossby wave sources through transient vorticity forcing.These associated Rossby waves propagates eastward along the polar front jet,resulting in the formation of a barotropic anomalous high-pressure system over Northeast Asia and inducing surface warming.While the soil moisture anomalies persist until June,their intensity weakens.Similarly,this favors the formation of an anomalous high-pressure system and Rossby wave source;however,their centers shift westward towards western Europe.The associated Rossby wave activity leads to the formation of a barotropic anomalous low-pressure system,causing cooling over Northeast Asia.Notably,the activity characteristics of Rossby waves (wave source,activity centers,and propagation pathway) associated with the soil moisture anomalies in eastern Europe exhibit distinct differences between May and June,closely tied to the atmospheric climatology over northern Eurasia.When soil moisture is high in May,the aforementioned physical processes exhibit reverse tendencies.
This study investigates the characteristics and underlying processes of the month-to-month reversal of air temperature anomalies in Northeast Asia during early summer (May to June) on the interannual timescales,focusing on the influences of soil moisture anomalies in eastern Europe.Utilizing observational and reanalysis data spanning from 1979 to 2020,the results reveal that the dominant mode of intermonthly variation in air temperature anomalies exhibits a reversal pattern,with warmer (colder) conditions in May and colder (warmer) conditions in June.This reversal mode is directly linked to circulation anomalies over Northeast Asia.Further analysis demonstrates that reduced soil moisture in eastern Europe during May contributes to a warmer May and a colder June in Northeast Asia.The potential physical processes driving these effects are explored.Lower soil moisture in May leads to local soil warming and subsequent warming of the lower troposphere.This,in turn,weakens (enhances) the lower tropospheric meridional temperature gradient and baroclinicity in the Mediterranean region (northern Europe).Consequently,high-frequency transient wave activity weakens (enhances),facilitating the formation of an anomalous high-pressure system over central and eastern Europe,thereby generating Rossby wave sources through transient vorticity forcing.These associated Rossby waves propagates eastward along the polar front jet,resulting in the formation of a barotropic anomalous high-pressure system over Northeast Asia and inducing surface warming.While the soil moisture anomalies persist until June,their intensity weakens.Similarly,this favors the formation of an anomalous high-pressure system and Rossby wave source;however,their centers shift westward towards western Europe.The associated Rossby wave activity leads to the formation of a barotropic anomalous low-pressure system,causing cooling over Northeast Asia.Notably,the activity characteristics of Rossby waves (wave source,activity centers,and propagation pathway) associated with the soil moisture anomalies in eastern Europe exhibit distinct differences between May and June,closely tied to the atmospheric climatology over northern Eurasia.When soil moisture is high in May,the aforementioned physical processes exhibit reverse tendencies.
2023,46(4): 549-560, DOI: 10.13878/j.cnki.dqkxxb.20220303001
Abstract:
The Tibetan Plateau exhibits complex train,resulting in significant variability in soil conditions across different regions.Gravel and soil organic matter have a substantial influence on soil thermal and hydraulic properties.In this study,we employ the regional climate model RegCM4.7 coupled with CLM4.5 to modify the surface data and implement a corresponding soil thermal and hydraulic parameterization scheme.We conduct two tests:one considering the influence of gravel (test2)and another considering the combined influence of gravel and organic matter (test3).Our results indicate that test2 significantly improves the simulation accuracy for the western part of the Plateau by incorporating gravel effects but exhibits poor performance for the eastern part.Test3 further enhances the simulation of shallow soil properties in the central and eastern regions based on test2.The regional average root mean square error of shallow soil temperature decreases from 2.11 ℃ to 0.47 ℃,and the regional average root mean square error of shallow soil moisture decreases from 0.05 mm3·mm-3 to 0.01 mm3·mm-3 when transitioning from test1 to test3.Furthermore,all three schemes successfully simulate the surface temperature of the Tibetan Plateau,with test3 exhibiting the smallest error.The root mean square error of the regional average decreases from 2.18 ℃ to 0.74 ℃,bringing it closer to the reanalysis data.
The Tibetan Plateau exhibits complex train,resulting in significant variability in soil conditions across different regions.Gravel and soil organic matter have a substantial influence on soil thermal and hydraulic properties.In this study,we employ the regional climate model RegCM4.7 coupled with CLM4.5 to modify the surface data and implement a corresponding soil thermal and hydraulic parameterization scheme.We conduct two tests:one considering the influence of gravel (test2)and another considering the combined influence of gravel and organic matter (test3).Our results indicate that test2 significantly improves the simulation accuracy for the western part of the Plateau by incorporating gravel effects but exhibits poor performance for the eastern part.Test3 further enhances the simulation of shallow soil properties in the central and eastern regions based on test2.The regional average root mean square error of shallow soil temperature decreases from 2.11 ℃ to 0.47 ℃,and the regional average root mean square error of shallow soil moisture decreases from 0.05 mm3·mm-3 to 0.01 mm3·mm-3 when transitioning from test1 to test3.Furthermore,all three schemes successfully simulate the surface temperature of the Tibetan Plateau,with test3 exhibiting the smallest error.The root mean square error of the regional average decreases from 2.18 ℃ to 0.74 ℃,bringing it closer to the reanalysis data.
2023,46(4): 561-574, DOI: 10.13878/j.cnki.dqkxxb.20210519001
Abstract:
This study analyzes the spatiotemporal variation of heat discomfort days characterized by Humidex and cold discomfort days represented by Wind Chill Index in different latitudes (high latitudes,middle latitudes,and low latitudes) of the northern hemisphere during 1961—2014,using NCEP/NCAR reanalysis data and simulations from six CMIP6 models.The investigation focuses on the attribution of these discomfort days.The results show a significant increase in the frequency of heat discomfort in the middle and low latitudes,and a significant decrease in the frequency of cold discomfort in the middle and high latitudes of the northern hemisphere.Furthermore,using the optimal fingerprint method,we find that the increased frequency of heat discomfort in middle latitude and the decreased frequency of cold discomfort in high latitude can be attributed to ALL,ANT,and GHG forcings,with GHG forcing dominating changes in the frequency of heat discomfort in mid-latitude areas and the frequency of cold discomfort in high-latitude areas.In the low latitudes,the significant increase in the frequency of heat discomfort can be attributed to anthropogenic greenhouse gas forcing,while AER has the opposite effect.The frequency of cold discomfort may be attributed to the internal variability of the climate system.In the future,the frequency of heat (cold) discomfort in the middle and low latitudes (middle and high latitudes) is expected to increase (decrease) under the uncoordinated and rapid development with higher radiative forcing.However,low radiative forcing and sustainable development can ensure a stable level of human comfort.
This study analyzes the spatiotemporal variation of heat discomfort days characterized by Humidex and cold discomfort days represented by Wind Chill Index in different latitudes (high latitudes,middle latitudes,and low latitudes) of the northern hemisphere during 1961—2014,using NCEP/NCAR reanalysis data and simulations from six CMIP6 models.The investigation focuses on the attribution of these discomfort days.The results show a significant increase in the frequency of heat discomfort in the middle and low latitudes,and a significant decrease in the frequency of cold discomfort in the middle and high latitudes of the northern hemisphere.Furthermore,using the optimal fingerprint method,we find that the increased frequency of heat discomfort in middle latitude and the decreased frequency of cold discomfort in high latitude can be attributed to ALL,ANT,and GHG forcings,with GHG forcing dominating changes in the frequency of heat discomfort in mid-latitude areas and the frequency of cold discomfort in high-latitude areas.In the low latitudes,the significant increase in the frequency of heat discomfort can be attributed to anthropogenic greenhouse gas forcing,while AER has the opposite effect.The frequency of cold discomfort may be attributed to the internal variability of the climate system.In the future,the frequency of heat (cold) discomfort in the middle and low latitudes (middle and high latitudes) is expected to increase (decrease) under the uncoordinated and rapid development with higher radiative forcing.However,low radiative forcing and sustainable development can ensure a stable level of human comfort.
2023,46(4): 575-586, DOI: 10.13878/j.cnki.dqkxxb.20220614001
Abstract:
Two moderate La Niña and El Niño events occurred in early 2008 and early 2016,respectively.During these two distinct El Niño/Southern Oscillation (ENSO) events,Yunnan experienced low temperatures and snowstorms.This study investigates the causes of these two extreme cold events during different ENSO events using statistical methods based on atmospheric circulation data,sea surface temperature (SST),and monthly temperature records from 124 observation stations in Yunnan.The findings are as follows:1) The extremely cold events in Yunnan were more pronounced in February for both 2008 and 2016.2) During the two different ENSO events in February,the variations in atmospheric circulation and temperature exhibited notable differences.In La Niña (El Niño) years,the Siberian high strengthened (weakened),with high geopotential height in the north (west) and low geopotential height in the south (east).The western Pacific subtropical high weakened (strengthened),and anomalous northerly (southerly) winds intensified on the northwest side of the Philippine anomalous cyclone (anticyclone).Additionally,the East Asian winter Monsoon was strong (weak),resulting in low (high) temperatures in the eastern region of Yunnan.3) The atmospheric circulation over the northeast Pacific responded to SST anomalies in the central and eastern equatorial Pacific in 2008 and 2016.Furthermore,the northerly current in the west of the Philippine cyclone triggered by the cold SST in the central and east of the equatorial Middle East Pacific significantly impacted the strengthening and southward activity of the East Asian winter monsoon in 2008,while the warm SST had no significant impact on the atmospheric circulation over the Philippines region in 2006.4) The effects of the Arctic Oscillation (AO) and Arctic Sea ice on the strengthening of the Siberian high in February 2008 and 2016 exhibited different characteristics.The positive phase of AO had a greater impact on the strengthening of the Siberian high in February 2008,whereas the reduction in Arctic Sea ice had a significant impact on the strengthening of the Siberian high in February 2016.
Two moderate La Niña and El Niño events occurred in early 2008 and early 2016,respectively.During these two distinct El Niño/Southern Oscillation (ENSO) events,Yunnan experienced low temperatures and snowstorms.This study investigates the causes of these two extreme cold events during different ENSO events using statistical methods based on atmospheric circulation data,sea surface temperature (SST),and monthly temperature records from 124 observation stations in Yunnan.The findings are as follows:1) The extremely cold events in Yunnan were more pronounced in February for both 2008 and 2016.2) During the two different ENSO events in February,the variations in atmospheric circulation and temperature exhibited notable differences.In La Niña (El Niño) years,the Siberian high strengthened (weakened),with high geopotential height in the north (west) and low geopotential height in the south (east).The western Pacific subtropical high weakened (strengthened),and anomalous northerly (southerly) winds intensified on the northwest side of the Philippine anomalous cyclone (anticyclone).Additionally,the East Asian winter Monsoon was strong (weak),resulting in low (high) temperatures in the eastern region of Yunnan.3) The atmospheric circulation over the northeast Pacific responded to SST anomalies in the central and eastern equatorial Pacific in 2008 and 2016.Furthermore,the northerly current in the west of the Philippine cyclone triggered by the cold SST in the central and east of the equatorial Middle East Pacific significantly impacted the strengthening and southward activity of the East Asian winter monsoon in 2008,while the warm SST had no significant impact on the atmospheric circulation over the Philippines region in 2006.4) The effects of the Arctic Oscillation (AO) and Arctic Sea ice on the strengthening of the Siberian high in February 2008 and 2016 exhibited different characteristics.The positive phase of AO had a greater impact on the strengthening of the Siberian high in February 2008,whereas the reduction in Arctic Sea ice had a significant impact on the strengthening of the Siberian high in February 2016.
2023,46(4): 587-599, DOI: 10.13878/j.cnki.dqkxxb.20220715002
Abstract:
To enhance our understanding of the causes behind interannual summer precipitation anomalies in North China and improve climate monitoring and prediction technologies,this study examines the relationship between the East Asian subtropical summer monsoon index (EAMI),the North China atmospheric dynamic rise index (HBDRI),and the summer precipitation in North China.Correlation analysis,synthesis,and circulation anomaly regression reconstruction methods are employed using summer precipitation data in North China and NCEP/NCAR reanalysis circulation data.The main findings are as follows:1) The EAMI and HBDRI exhibit a significant correspondence with summer precipitation in North China.Stronger values of both indices are associated with above-average summer precipitation in North China,while weaker values are associated with below-average summer precipitation.In cases where the strength of the two indices is inconsistent,regional precipitation in North China may be above average,but the overall precipitation in the entire region remains relatively normal.2) Anomalies in summer precipitation in North China result from the combined effects of the East Asian subtropical summer monsoon and the upward motion of atmospheric dynamics in North China.In years with stronger EAMI and HDBRI values,the Baikal Lake trough deepens at the 500 hPa level during summer,the Northwest Pacific subtropical high shifts northward,and North China falls under influence of a circulation pattern characterized by a high-pressure system in the east and a low-pressure system in the west.Consequently,the movement of the western low trough eastward is hindered,leading to a sustained upward motion of the atmosphere over North China.This pattern is accompanied by an increased intensity of the Indian summer monsoon and the East Asian subtropical summer monsoon at the 850 hPa level.During this period,the westerly wind water vapor transport from the tropical Indian Ocean,the southerly wind water vapor transport from the East Asian subtropical region,or the southeast wind water vapor transport strengthens,ensuring an ample supply of water vapor to North China.Such a configuration of high-and low-level circulations is highly conducive to generating increased summer precipitation in North China.Conversely,unusually below-average summer precipitation occurs when the aforementioned conditions are not met.3) The stronger values of the EAMI and HBDRI during the early April-May period can serve as climate monitoring and prediction indicators for abnormally high summer precipitation in North China.
To enhance our understanding of the causes behind interannual summer precipitation anomalies in North China and improve climate monitoring and prediction technologies,this study examines the relationship between the East Asian subtropical summer monsoon index (EAMI),the North China atmospheric dynamic rise index (HBDRI),and the summer precipitation in North China.Correlation analysis,synthesis,and circulation anomaly regression reconstruction methods are employed using summer precipitation data in North China and NCEP/NCAR reanalysis circulation data.The main findings are as follows:1) The EAMI and HBDRI exhibit a significant correspondence with summer precipitation in North China.Stronger values of both indices are associated with above-average summer precipitation in North China,while weaker values are associated with below-average summer precipitation.In cases where the strength of the two indices is inconsistent,regional precipitation in North China may be above average,but the overall precipitation in the entire region remains relatively normal.2) Anomalies in summer precipitation in North China result from the combined effects of the East Asian subtropical summer monsoon and the upward motion of atmospheric dynamics in North China.In years with stronger EAMI and HDBRI values,the Baikal Lake trough deepens at the 500 hPa level during summer,the Northwest Pacific subtropical high shifts northward,and North China falls under influence of a circulation pattern characterized by a high-pressure system in the east and a low-pressure system in the west.Consequently,the movement of the western low trough eastward is hindered,leading to a sustained upward motion of the atmosphere over North China.This pattern is accompanied by an increased intensity of the Indian summer monsoon and the East Asian subtropical summer monsoon at the 850 hPa level.During this period,the westerly wind water vapor transport from the tropical Indian Ocean,the southerly wind water vapor transport from the East Asian subtropical region,or the southeast wind water vapor transport strengthens,ensuring an ample supply of water vapor to North China.Such a configuration of high-and low-level circulations is highly conducive to generating increased summer precipitation in North China.Conversely,unusually below-average summer precipitation occurs when the aforementioned conditions are not met.3) The stronger values of the EAMI and HBDRI during the early April-May period can serve as climate monitoring and prediction indicators for abnormally high summer precipitation in North China.
2023,46(4): 600-614, DOI: 10.13878/j.cnki.dqkxxb.20220727001
Abstract:
This study analyzes the frontogenesis characteristics of rainstorms during the Meiyu period in 2020 using ERA5 reanalysis data and the precipitation data from automatic stations in Jiangsu Province.The main results are as follows:1) The characteristics of frontogenesis during the Meiyu period in 2020 are significant.Heavy rain is associated with middle-low frontogenesis,with deformation frontogenesis being the main contributor.2) Heavy rainfall during the Meiyu period can be categorized into two types.Severe convective rainstorms exhibit a larger frontogenesis range,higher development,greater intensity,and more overlap between total frontogenesis and decomposition terms.However,stable rainfall shows opposite characteristics.3) Two typical cases,namely the strong convective rainfall event on “6.28” and the stable rainfall event on “7.11” are selected.Frontogenesis occurs along shear lines and in regions of significant pseudo-equivalent potential temperature gradient.Strong convective rainfall is observed near the main frontal zone and in high-energy zones of pseudo-equivalent potential temperature,indicating the presence of multiple secondary frontogenesis centers.Stable heavy precipitation,on the other hand,is concentrated near the main frontal zone.These different rainfall distributions arise from variations in triggering mechanism and precipitation properties.4) The vertical front zone in both processes tilts northward from low to high.In the “6.28” process,a notable transport of warm and moist airflow is observed on the south side of the frontal zone,with strong upward motion within the frontal zone.In contrast,the “7.11” process exhibits less pronounced features and weaker convection.The magnitude and impact of frontogenesis differ across various precipitation processes and stages.Rainstorms are primarily generated by divergence and deformation frontogenesis,while the tilting term frontolysis in convective precipitation and frontogenesis in stable precipitation.Quantitative analysis of each decomposition term reveals that low-level divergence and deformation frontogenesis initially increase and then decrease in both processes.Deformation and divergence frontogenesis below 700 hPa are the main contributors,while the middle-high atmosphere experiences frontolysis.
This study analyzes the frontogenesis characteristics of rainstorms during the Meiyu period in 2020 using ERA5 reanalysis data and the precipitation data from automatic stations in Jiangsu Province.The main results are as follows:1) The characteristics of frontogenesis during the Meiyu period in 2020 are significant.Heavy rain is associated with middle-low frontogenesis,with deformation frontogenesis being the main contributor.2) Heavy rainfall during the Meiyu period can be categorized into two types.Severe convective rainstorms exhibit a larger frontogenesis range,higher development,greater intensity,and more overlap between total frontogenesis and decomposition terms.However,stable rainfall shows opposite characteristics.3) Two typical cases,namely the strong convective rainfall event on “6.28” and the stable rainfall event on “7.11” are selected.Frontogenesis occurs along shear lines and in regions of significant pseudo-equivalent potential temperature gradient.Strong convective rainfall is observed near the main frontal zone and in high-energy zones of pseudo-equivalent potential temperature,indicating the presence of multiple secondary frontogenesis centers.Stable heavy precipitation,on the other hand,is concentrated near the main frontal zone.These different rainfall distributions arise from variations in triggering mechanism and precipitation properties.4) The vertical front zone in both processes tilts northward from low to high.In the “6.28” process,a notable transport of warm and moist airflow is observed on the south side of the frontal zone,with strong upward motion within the frontal zone.In contrast,the “7.11” process exhibits less pronounced features and weaker convection.The magnitude and impact of frontogenesis differ across various precipitation processes and stages.Rainstorms are primarily generated by divergence and deformation frontogenesis,while the tilting term frontolysis in convective precipitation and frontogenesis in stable precipitation.Quantitative analysis of each decomposition term reveals that low-level divergence and deformation frontogenesis initially increase and then decrease in both processes.Deformation and divergence frontogenesis below 700 hPa are the main contributors,while the middle-high atmosphere experiences frontolysis.
2023,46(4): 615-629, DOI: 10.13878/j.cnki.dqkxxb.20210130001
Abstract:
This study evaluates the performance of several existing tropical cyclone (TC) genesis potential indices (GPIs) in reproducing the observed TC genesis frequency (TCGF) in the North Atlantic and western North Pacific (WNP) from 1979 to 2017.The results demonstrate that the existing GPIs can reasonably replicate the climatological distribution,annual cycle,and interannual variability of TCGF in the North Atlantic.However,they fail to reproduce the interannual variability of TCGF in the WNP.To address this limitation,a modified GPI is developed for the WNP,utilizing best-track TC data and ERA-Interim reanalysis data spanning 1979—2017.The modified GPI incorporates earth vorticity (the Coriolis parameter) and relative vorticity separately instead of absolute vorticity and excludes relative humidity,which is commonly used in existing GPIs.Compared with the existing GPIs,the modified GPI can reproduce not only the climatological distribution and annual cycle but also the interannual variability of TCGF in the WNP,particularly in the southeastern region.Additionally,the modified GPI is evaluated using NCEP/NCAR,JRA-55,and ERA5 reanalysis datasets,demonstrating consistent and improved performance in reproducing the interannual variability of TCGF,especially when employing JRA-55 or NCEP/NCAR reanalysis datasets.
This study evaluates the performance of several existing tropical cyclone (TC) genesis potential indices (GPIs) in reproducing the observed TC genesis frequency (TCGF) in the North Atlantic and western North Pacific (WNP) from 1979 to 2017.The results demonstrate that the existing GPIs can reasonably replicate the climatological distribution,annual cycle,and interannual variability of TCGF in the North Atlantic.However,they fail to reproduce the interannual variability of TCGF in the WNP.To address this limitation,a modified GPI is developed for the WNP,utilizing best-track TC data and ERA-Interim reanalysis data spanning 1979—2017.The modified GPI incorporates earth vorticity (the Coriolis parameter) and relative vorticity separately instead of absolute vorticity and excludes relative humidity,which is commonly used in existing GPIs.Compared with the existing GPIs,the modified GPI can reproduce not only the climatological distribution and annual cycle but also the interannual variability of TCGF in the WNP,particularly in the southeastern region.Additionally,the modified GPI is evaluated using NCEP/NCAR,JRA-55,and ERA5 reanalysis datasets,demonstrating consistent and improved performance in reproducing the interannual variability of TCGF,especially when employing JRA-55 or NCEP/NCAR reanalysis datasets.
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在线获得:May 08, 2023, DOI: 10.13878/j.cnki.dqkxxb.20230501007
Abstract:
From March to April in 2023, 9 dust weather processes occurred in China.The processes from 19 to 24 March and from 9 to 13 April reached the level of strong sandstorm and sandstorm respectively, bringing adverse impacts on population health, ecological envi-ronment and transportation.The anomalous Eurasian atmospheric circulations showed a zonal distribution from the late winter to early spring, the Siberian high and the East Asian trough were weak, and the area around Mongolia was controlled by the high pressure anom-aly, which resulted in the continuous warm surface air temperature and soil temperature in the dust source area (the second highest since 1980).In addition, the lower troposphere also lacked water vapor transporting to the sand source, resulting in significantly less precipita-tion in the winter and spring of 2023 (the lowest in history since 1980).The continuous warm and dry climate conditions in winter and spring resulted in a large number of dry and loose gravel in the dust source area from February to March in 2023, which provided ex-tremely favorable dust source conditions for the occurrence of sandstorms.The synoptic disturbance systems that triggered the sandstorms in March 19—24 and April 9—13 were both Mongolian cyclones.However, the two Mongolian cyclones and their configuration with the rear cold high were different, which directly caused the differences in the intensity, path and duration of the two sandstorms.From 19 to 24 March, the dust process reached the level of strong sandstorm, causing PM10 concentrations in Beijing and Harbin to exceed 2000 and 3600 μg·m?3 respectively.The sandstorm from 9 to 13 April not only affected Northeast and North China, but also caused a significant increase in PM10 concentration in cities south of the Yangtze River, such as Hangzhou and Fuzhou.Moreover, the research emphases of dust events from the aspects of climate cumulative effect and synoptic disturbance mechanism are analyzed, and the necessity and key points of conducting subseasonal-seasonal and interdecadal prediction of dust events are discussed.Furthermore, severe sandstorms in 2021 and 2023 also raise the scientific question, "Have dust events entered a new period of activity?".To answer this question, it is neces-sary to study the interdecadal mechanism and prediction of dust change, and also to predict the future change of dust event trend to a cer-tain extent.
From March to April in 2023, 9 dust weather processes occurred in China.The processes from 19 to 24 March and from 9 to 13 April reached the level of strong sandstorm and sandstorm respectively, bringing adverse impacts on population health, ecological envi-ronment and transportation.The anomalous Eurasian atmospheric circulations showed a zonal distribution from the late winter to early spring, the Siberian high and the East Asian trough were weak, and the area around Mongolia was controlled by the high pressure anom-aly, which resulted in the continuous warm surface air temperature and soil temperature in the dust source area (the second highest since 1980).In addition, the lower troposphere also lacked water vapor transporting to the sand source, resulting in significantly less precipita-tion in the winter and spring of 2023 (the lowest in history since 1980).The continuous warm and dry climate conditions in winter and spring resulted in a large number of dry and loose gravel in the dust source area from February to March in 2023, which provided ex-tremely favorable dust source conditions for the occurrence of sandstorms.The synoptic disturbance systems that triggered the sandstorms in March 19—24 and April 9—13 were both Mongolian cyclones.However, the two Mongolian cyclones and their configuration with the rear cold high were different, which directly caused the differences in the intensity, path and duration of the two sandstorms.From 19 to 24 March, the dust process reached the level of strong sandstorm, causing PM10 concentrations in Beijing and Harbin to exceed 2000 and 3600 μg·m?3 respectively.The sandstorm from 9 to 13 April not only affected Northeast and North China, but also caused a significant increase in PM10 concentration in cities south of the Yangtze River, such as Hangzhou and Fuzhou.Moreover, the research emphases of dust events from the aspects of climate cumulative effect and synoptic disturbance mechanism are analyzed, and the necessity and key points of conducting subseasonal-seasonal and interdecadal prediction of dust events are discussed.Furthermore, severe sandstorms in 2021 and 2023 also raise the scientific question, "Have dust events entered a new period of activity?".To answer this question, it is neces-sary to study the interdecadal mechanism and prediction of dust change, and also to predict the future change of dust event trend to a cer-tain extent.
在线获得:April 06, 2023, DOI: 10.13878/j.cnki.dqkxxb.20220805002
Abstract:
Southeast Asia has a complex topography and a large population. The response of extreme precipitation events to global warming is sensitive and its future evolutionary characteristics are widely valued. In this study, 26 global climate models (GCMs) are used to present projected change in precipitation extremes over Southeast Asia at the end of 21st century based on the Coupled Model Intercomparison Project phase 6 (CMIP6) simulations. The thermodynamic and dynamic contributions to future changes in precipitation are analyzed by decomposition of moisture budget equation. The multi-model ensemble medians show that, compared with the historical reference period (1985—2014), the frequency and intensity of climatological precipitation and precipitation extremes in most of Southeast Asia are obviously increased at the end of 21st century (2070—2099) under SSP2-4.5 and SSP5-8.5 scenarios. The variation of precipitation extremes shows significant spatial differences under the global warming. Precipitation extremes with short duration and high intensity will occur in the Kalimantan. In southern Sumatra, the total precipitation of wet days (PRCPTOT) tends to decrease significantly and the occurrence of consecutive dry days (CDD) become more frequent. Except for heavy precipitation days (R10mm), the change of extreme precipitation indices with more pronounced magnitudes under SSP5-8.5 scenario than SSP2-4.5 scenario. The contribution rate of heavy precipitation (R95pTOT) increased by 22% (41%) under SSP2-4.5 (SSP5-8.5) scenario. Quantitative analysis of moisture budget equation shows that, thermodynamic and dynamic effects mainly result in the precipitation climatological changes at the end of 21st century. Compared with the large-scale circulation changes, the thermodynamic component with higher inter-model consistency is the main contribution term. Under SSP2-4.5 (SSP5-8.5) scenario, the contribution of thermodynamic effects accounts for 65% (64%) of the P-E (precipitation minus evaporation) changes. However, the dynamic effects show a counteracting trend to the changes of P-E, which contributes 35% (36%). Moisture convergence caused by atmospheric specific humidity changes is considered as the dominating factor of projected precipitation increase.
Southeast Asia has a complex topography and a large population. The response of extreme precipitation events to global warming is sensitive and its future evolutionary characteristics are widely valued. In this study, 26 global climate models (GCMs) are used to present projected change in precipitation extremes over Southeast Asia at the end of 21st century based on the Coupled Model Intercomparison Project phase 6 (CMIP6) simulations. The thermodynamic and dynamic contributions to future changes in precipitation are analyzed by decomposition of moisture budget equation. The multi-model ensemble medians show that, compared with the historical reference period (1985—2014), the frequency and intensity of climatological precipitation and precipitation extremes in most of Southeast Asia are obviously increased at the end of 21st century (2070—2099) under SSP2-4.5 and SSP5-8.5 scenarios. The variation of precipitation extremes shows significant spatial differences under the global warming. Precipitation extremes with short duration and high intensity will occur in the Kalimantan. In southern Sumatra, the total precipitation of wet days (PRCPTOT) tends to decrease significantly and the occurrence of consecutive dry days (CDD) become more frequent. Except for heavy precipitation days (R10mm), the change of extreme precipitation indices with more pronounced magnitudes under SSP5-8.5 scenario than SSP2-4.5 scenario. The contribution rate of heavy precipitation (R95pTOT) increased by 22% (41%) under SSP2-4.5 (SSP5-8.5) scenario. Quantitative analysis of moisture budget equation shows that, thermodynamic and dynamic effects mainly result in the precipitation climatological changes at the end of 21st century. Compared with the large-scale circulation changes, the thermodynamic component with higher inter-model consistency is the main contribution term. Under SSP2-4.5 (SSP5-8.5) scenario, the contribution of thermodynamic effects accounts for 65% (64%) of the P-E (precipitation minus evaporation) changes. However, the dynamic effects show a counteracting trend to the changes of P-E, which contributes 35% (36%). Moisture convergence caused by atmospheric specific humidity changes is considered as the dominating factor of projected precipitation increase.
在线获得:April 06, 2023, DOI: 10.13878/j.cnki.dqkxxb.20220715001
Abstract:
Based on the dataset of precipitation phenomenon instrument in Zhengzhou, the dual polarization radars, the conventional observation and the China’s First Generation Global Atmosphere and Land Reanalysis data, the microphysical characteristics of “7·20” extremely heavy rainfall in Zhengzhou were analyzed. The extremely heavy rainfall was affected by multiscale weather systems, providing favorable environmental conditions for the formation of complex microphysical characteristics. The results showed that the raindrop size distributions changed significantly with time, and values of the raindrop size distribution parameters were widely distributed, covering the distribution area from continental convective precipitation to maritime convective precipitation. The number density of small drops was much higher than that of common convective precipitation in East Asia and the average value in South China in summer, and a large number of large drops also existed, leading to the higher precipitation efficiency during the strongest precipitation period from 16:00 to 17:00 on the 20th July. The low-centroid structure of convective storm was observed by dual polarization radar, showing the typical characteristics of warm cloud. The intense warm-rain processes below the 0℃ layer played an important role in the formation of the extremely heavy rainfall because of the melting of lots of ice particles and high efficiency for the growth of raindrops.
Based on the dataset of precipitation phenomenon instrument in Zhengzhou, the dual polarization radars, the conventional observation and the China’s First Generation Global Atmosphere and Land Reanalysis data, the microphysical characteristics of “7·20” extremely heavy rainfall in Zhengzhou were analyzed. The extremely heavy rainfall was affected by multiscale weather systems, providing favorable environmental conditions for the formation of complex microphysical characteristics. The results showed that the raindrop size distributions changed significantly with time, and values of the raindrop size distribution parameters were widely distributed, covering the distribution area from continental convective precipitation to maritime convective precipitation. The number density of small drops was much higher than that of common convective precipitation in East Asia and the average value in South China in summer, and a large number of large drops also existed, leading to the higher precipitation efficiency during the strongest precipitation period from 16:00 to 17:00 on the 20th July. The low-centroid structure of convective storm was observed by dual polarization radar, showing the typical characteristics of warm cloud. The intense warm-rain processes below the 0℃ layer played an important role in the formation of the extremely heavy rainfall because of the melting of lots of ice particles and high efficiency for the growth of raindrops.
在线获得:April 06, 2023, DOI: 10.13878/j.cnki.dqkxxb.20220715002
Abstract:
In order to understand the causes of summer precipitation anomalies in North China and improve climate monitoring and prediction technology, based on the summer precipitation data in North China and NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data from 1961 to 2021, using the methods of correlation, synthesis and circulation anomaly reconstruction, the circulation background of summer (June -August) precipitation anomaly in North China and the relationship between East Asian subtropical summer monsoon, North China dynamic rise index and summer precipitation in North China are analyzed. The results show that: (1) the circulation conditions of abnormal precipitation in North China in summer are that the high ridge of Ural Mountain at 500hPa in summer is stronger, the Baikal Lake trough is deeper, the subtropical high in the Northwest Pacific is north by west near the Korean Peninsula, and North China is in the circulation situation of "high in the East and low in the west", so the dynamic rising conditions are favorable. At the same time, the 850hPa Indian monsoon is stronger, the East Asian subtropical summer monsoon is significantly stronger, and the water vapor source in North China is sufficient. (2) The East Asian subtropical summer monsoon index and North China dynamic rise index defined in this paper have a good indication of summer precipitation anomalies in North China. When the two indexes are stronger, the summer precipitation in North China is abnormally more. If both indexes are weak, the summer precipitation in North China is abnormally less. If the two indexes are inconsistent, the summer precipitation in North China is basically normal. (3) The abnormally more or less summer rainfall in North China is the result of the synergy of the East Asian subtropical summer monsoon and the dynamic upward movement in North China. The subtropical summer monsoon in East Asia is stronger (the dynamic upward movement in North China is stronger), the Baikal trough in the 500hPa layer is deepened, the subtropical high in the Northwest Pacific is north by west, and North China is under the control of the circulation of "high in the East and low in the West", so the dynamic upward conditions are favorable. At the same time, the Indian summer monsoon at 850hPa and the subtropical summer monsoon in East Asia are relatively strong, which will strengthen the water vapor transmission of the west wind in the tropical Indian Ocean and the south wind in the subtropical region of East Asia, and the water vapor source in North China is sufficient. The above situation will cause abnormally more summer precipitation in North China. On the contrary, the summer precipitation in North China will be abnormally less. (4) From April to May in the early stage, the Baikal trough in the 500hPa layer deepened, the subtropical high in the Northwest Pacific was northerly, and the southerly wind in East Asia in the 850hPa layer was significantly stronger, which can be used as a climate monitoring and prediction index for the abnormally more summer precipitation in North China.
In order to understand the causes of summer precipitation anomalies in North China and improve climate monitoring and prediction technology, based on the summer precipitation data in North China and NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data from 1961 to 2021, using the methods of correlation, synthesis and circulation anomaly reconstruction, the circulation background of summer (June -August) precipitation anomaly in North China and the relationship between East Asian subtropical summer monsoon, North China dynamic rise index and summer precipitation in North China are analyzed. The results show that: (1) the circulation conditions of abnormal precipitation in North China in summer are that the high ridge of Ural Mountain at 500hPa in summer is stronger, the Baikal Lake trough is deeper, the subtropical high in the Northwest Pacific is north by west near the Korean Peninsula, and North China is in the circulation situation of "high in the East and low in the west", so the dynamic rising conditions are favorable. At the same time, the 850hPa Indian monsoon is stronger, the East Asian subtropical summer monsoon is significantly stronger, and the water vapor source in North China is sufficient. (2) The East Asian subtropical summer monsoon index and North China dynamic rise index defined in this paper have a good indication of summer precipitation anomalies in North China. When the two indexes are stronger, the summer precipitation in North China is abnormally more. If both indexes are weak, the summer precipitation in North China is abnormally less. If the two indexes are inconsistent, the summer precipitation in North China is basically normal. (3) The abnormally more or less summer rainfall in North China is the result of the synergy of the East Asian subtropical summer monsoon and the dynamic upward movement in North China. The subtropical summer monsoon in East Asia is stronger (the dynamic upward movement in North China is stronger), the Baikal trough in the 500hPa layer is deepened, the subtropical high in the Northwest Pacific is north by west, and North China is under the control of the circulation of "high in the East and low in the West", so the dynamic upward conditions are favorable. At the same time, the Indian summer monsoon at 850hPa and the subtropical summer monsoon in East Asia are relatively strong, which will strengthen the water vapor transmission of the west wind in the tropical Indian Ocean and the south wind in the subtropical region of East Asia, and the water vapor source in North China is sufficient. The above situation will cause abnormally more summer precipitation in North China. On the contrary, the summer precipitation in North China will be abnormally less. (4) From April to May in the early stage, the Baikal trough in the 500hPa layer deepened, the subtropical high in the Northwest Pacific was northerly, and the southerly wind in East Asia in the 850hPa layer was significantly stronger, which can be used as a climate monitoring and prediction index for the abnormally more summer precipitation in North China.
在线获得:April 06, 2023, DOI: 10.13878/j.cnki.dqkxxb.20221212001
Abstract:
During the Dragon-boat precipitation period in 2022 (from May 21 to June 21), the average precipitation in South China is 472.5 mm, which is the second largest in the same period in history, it is the third largest in Guangdong，Guangxi is the largest in the same period since there are meteorological records history in 1951. Under its influence, River basin flood occurs in the Pearl River basin, and catastrophic floods occurs in the Beijiang River basin. Using the daily precipitation data of 192 national meteorological observation stations in South China, NCEP/NCAR atmospheric circulation，atmospheric outward long wave radiation(OLR) data and NOAA monthly scale SST reanalysis data, the characteristics of South China Dragon-boat precipitation anomaly in 2022 and its relationship with atmospheric circulation and sea surface temperature are studied by using correlation and composite analysis methods. The results show that the East Asia Trough and the Northeast Cold Vortex are significantly strengthened, the cold air affecting South China is strong. The Western Pacific Subtropical High and the South Branch Trough are both relatively strong, and there is significant water vapor convergence in South China during the Dragon-boat precipitation period in 2022. The atmospheric response to the La Nina event is obvious in 2022, and the Walker circulation is enhanced. The convection in South China strengthened obviously. An abnormal anticyclone circulation was in the east of the Philippines. The Western Pacific Subtropical High becomes stronger, the southwest wind on its northwest side is stronger. Water vapor transmission to South China has increased significantly, Water vapor transmission to South China increased significantly. the significant enhancement of water vapor transport to South China. A significant upward movement at the same time in South China. The abnormality of atmospheric circulation and SST lead to the extreme Dragon-boat precipitation in South China in 2022.
During the Dragon-boat precipitation period in 2022 (from May 21 to June 21), the average precipitation in South China is 472.5 mm, which is the second largest in the same period in history, it is the third largest in Guangdong，Guangxi is the largest in the same period since there are meteorological records history in 1951. Under its influence, River basin flood occurs in the Pearl River basin, and catastrophic floods occurs in the Beijiang River basin. Using the daily precipitation data of 192 national meteorological observation stations in South China, NCEP/NCAR atmospheric circulation，atmospheric outward long wave radiation(OLR) data and NOAA monthly scale SST reanalysis data, the characteristics of South China Dragon-boat precipitation anomaly in 2022 and its relationship with atmospheric circulation and sea surface temperature are studied by using correlation and composite analysis methods. The results show that the East Asia Trough and the Northeast Cold Vortex are significantly strengthened, the cold air affecting South China is strong. The Western Pacific Subtropical High and the South Branch Trough are both relatively strong, and there is significant water vapor convergence in South China during the Dragon-boat precipitation period in 2022. The atmospheric response to the La Nina event is obvious in 2022, and the Walker circulation is enhanced. The convection in South China strengthened obviously. An abnormal anticyclone circulation was in the east of the Philippines. The Western Pacific Subtropical High becomes stronger, the southwest wind on its northwest side is stronger. Water vapor transmission to South China has increased significantly, Water vapor transmission to South China increased significantly. the significant enhancement of water vapor transport to South China. A significant upward movement at the same time in South China. The abnormality of atmospheric circulation and SST lead to the extreme Dragon-boat precipitation in South China in 2022.
在线获得:March 22, 2023, DOI: 10.13878/j.cnki.dqkxxb.20221025001
Abstract:
Based on the observational and reanalysis data during 1979—2020, this study investigated the basic features of the month-to-month reversal of air temperature anomalies in Northeast Asia in early summer (May to June) on the interannual timescales, as well as the effects of soil moisture anomalies in eastern Europe and the possible physical processes. The results show that the predominant mode of the intermonthly variation of air temperature anomalies in Northeast Asia in early summer is the reversal mode, that is warmer (colder) in May and colder (warmer) in June; and its formation is directly derived from the reversal of circulation anomalies over Northeast Asia. Further analysis indicates that the lower soil moisture in eastern Europe in May tends to lead to a warmer May and colder June in Northeast Asia. With the possible physical processes as following: lower soil moisture in May leads to local soil temperature and lower troposphere warming, which in turn causes a weakening (enhancement) of the lower tropospheric meridional temperature gradient and baroclinicity in the Mediterranean region (northern Europe). Correspondingly, high-frequency transient wave activity weakens (enhances) and facilitates the formation of an anomalous high over central and eastern Europe and hence Rossby wave source via transient vorticity forcing. The associated Rossby wave travels eastward along the polar front jet, resulting in a barotropic anomalous high over Northeast Asia and resultant surface warming. The soil moisture anomalies can persist until June but weaken in intensity. Similarly, it favors the formation of an anomalous high and Rossby wave source, but their center shifts westward to western Europe. The related Rossby wave activity leads to a barotropic anomalous low and hence cooling over Northeast Asia. There are obvious differences in the activity characteristics of Rossby waves (wave source, activity centers, and propagation pathway) associated with the soil moisture anomalies in eastern Europe in May and June, which are closely related to the difference in atmospheric climatology over northern Eurasia. When the soil moisture in eastern Europe is high in May, the above physical processes are roughly reversed.
Based on the observational and reanalysis data during 1979—2020, this study investigated the basic features of the month-to-month reversal of air temperature anomalies in Northeast Asia in early summer (May to June) on the interannual timescales, as well as the effects of soil moisture anomalies in eastern Europe and the possible physical processes. The results show that the predominant mode of the intermonthly variation of air temperature anomalies in Northeast Asia in early summer is the reversal mode, that is warmer (colder) in May and colder (warmer) in June; and its formation is directly derived from the reversal of circulation anomalies over Northeast Asia. Further analysis indicates that the lower soil moisture in eastern Europe in May tends to lead to a warmer May and colder June in Northeast Asia. With the possible physical processes as following: lower soil moisture in May leads to local soil temperature and lower troposphere warming, which in turn causes a weakening (enhancement) of the lower tropospheric meridional temperature gradient and baroclinicity in the Mediterranean region (northern Europe). Correspondingly, high-frequency transient wave activity weakens (enhances) and facilitates the formation of an anomalous high over central and eastern Europe and hence Rossby wave source via transient vorticity forcing. The associated Rossby wave travels eastward along the polar front jet, resulting in a barotropic anomalous high over Northeast Asia and resultant surface warming. The soil moisture anomalies can persist until June but weaken in intensity. Similarly, it favors the formation of an anomalous high and Rossby wave source, but their center shifts westward to western Europe. The related Rossby wave activity leads to a barotropic anomalous low and hence cooling over Northeast Asia. There are obvious differences in the activity characteristics of Rossby waves (wave source, activity centers, and propagation pathway) associated with the soil moisture anomalies in eastern Europe in May and June, which are closely related to the difference in atmospheric climatology over northern Eurasia. When the soil moisture in eastern Europe is high in May, the above physical processes are roughly reversed.
在线获得:February 17, 2023, DOI: 10.13878/j.cnki.dqkxxb.20220324001
Abstract:
Based on the daily observations collected by National Meteorological Information Centre since 1919, the homogenized daily maximum and minimum temperature series during the period of 1912-2019 were established for Baoding in Hebei Province. Firstly, the error data due to manual observation or recording, instrument malfunctions and digital inputs were removed by quality control. Then, the missing observations were interpolated by standardized series method using the homogenized daily temperature data in Tianjin over century-long scale. Lastly, several significant breakpoints caused by changes in interpolation, station relocation and instrument manufacturers were detected by penalized maximal t test (PMT) with annual and monthly reference series constructed by two means, and adjusted by Quantile Matching (QM) adjustment with daily reference series from Berkeley Earth-daily data. It was found that the characteristics of inter-annual, decadal and trend changes were consistent with those fromBerkeley Earth-monthly、CRUTS4.03 and GHCNV3. And the characteristics of warming change induced by the rapid urban development in Baoding region have well been reflected, simultaneously compared with the whole Beijing-Tianjin-Hebei region. In addition, the warming change of annual and seasonal temperature extremes in Baoding have also increased significantly since 1912, the warming trends of annual and autumn lowest minimum temperature (TNn) were 0.340℃/10a and 0.404℃/10a (95% significance level), respectively, and the corresponding diurnal temperature range (DTR) are -0.118℃/10a and -0.215℃/10a (95% significance level).
Based on the daily observations collected by National Meteorological Information Centre since 1919, the homogenized daily maximum and minimum temperature series during the period of 1912-2019 were established for Baoding in Hebei Province. Firstly, the error data due to manual observation or recording, instrument malfunctions and digital inputs were removed by quality control. Then, the missing observations were interpolated by standardized series method using the homogenized daily temperature data in Tianjin over century-long scale. Lastly, several significant breakpoints caused by changes in interpolation, station relocation and instrument manufacturers were detected by penalized maximal t test (PMT) with annual and monthly reference series constructed by two means, and adjusted by Quantile Matching (QM) adjustment with daily reference series from Berkeley Earth-daily data. It was found that the characteristics of inter-annual, decadal and trend changes were consistent with those fromBerkeley Earth-monthly、CRUTS4.03 and GHCNV3. And the characteristics of warming change induced by the rapid urban development in Baoding region have well been reflected, simultaneously compared with the whole Beijing-Tianjin-Hebei region. In addition, the warming change of annual and seasonal temperature extremes in Baoding have also increased significantly since 1912, the warming trends of annual and autumn lowest minimum temperature (TNn) were 0.340℃/10a and 0.404℃/10a (95% significance level), respectively, and the corresponding diurnal temperature range (DTR) are -0.118℃/10a and -0.215℃/10a (95% significance level).
在线获得:December 06, 2022, DOI: 10.13878/j.cnki.dqkxxb. 20210324001
Abstract:
A Rapid Refresh Hybrid system was constructed based on the Weather Research and Forecasting(WRF) Model,WRF Hybrid Data Assimilation system and Ensemble Transform Kalman Filter(ETKF),with assimilating both Wind Profile Radar Detection(WPRD) data and Microwave Radiometer(MWR) data.Experiments were performed for the study of the impact of 4 important parameters on the system,which are 2 tuning factors of static background error, localization scale and ensemble weighting factor,and contrast research was carried on to the results of Hybrid and 3DVAR schemes.Some encouraged conclusions were given as follows:Tuning these 4 parameters could improve performance of the Rapid Refresh Hybrid system.The analysis and forecast of Hybrid with pa-rameters not tuned were better than those of 3DVAR, and the results of Hybrid with parameters tuned were the best.
A Rapid Refresh Hybrid system was constructed based on the Weather Research and Forecasting(WRF) Model,WRF Hybrid Data Assimilation system and Ensemble Transform Kalman Filter(ETKF),with assimilating both Wind Profile Radar Detection(WPRD) data and Microwave Radiometer(MWR) data.Experiments were performed for the study of the impact of 4 important parameters on the system,which are 2 tuning factors of static background error, localization scale and ensemble weighting factor,and contrast research was carried on to the results of Hybrid and 3DVAR schemes.Some encouraged conclusions were given as follows:Tuning these 4 parameters could improve performance of the Rapid Refresh Hybrid system.The analysis and forecast of Hybrid with pa-rameters not tuned were better than those of 3DVAR, and the results of Hybrid with parameters tuned were the best.
在线获得:December 06, 2022, DOI: 10.13878/j.cnki.dqkxxb. 20220306001
Abstract:
Based on the Global Ensemble Prediction System in China Meteorological Administration (CMA-GEPS), the extreme Meiyu process over China in 2020 was evaluated. Results show that, during the Meiyu season, a strong and stable western Pacific subtropical high (WPSH) and a gradually strengthened East Asian summer monsoon provide favorable dynamic and moisture conditions for strong rainfall. For the western Pacific subtropical high, CMA-GEPS could skillfully forecast the evolution trend of WPSH index with 7-9 leading days; the CMA-GEPS prediction skills of WPSH strength and area are about the same level as the results from the NCEP ensemble prediction system, and the WPSH strength presents the weaker bias compared with the observation; the prediction skills of ridge line and western boundary index with CMA-GEPS are comparable with the results from ECMWF ensemble prediction system, and the forecasting bias is mainly attributed to the more southward location of ridge line and more eastward center position of western boundary. For the East Asian summer monsoon, CMA-GEPS could skillfully predict the index with 9 leading days, which was two days earlier than the control forecast. The CMA-GEPS control forecasting bias is mainly attributed to the weaker precipitation intensity and more southward location of strong rainfall belt, and also the control forecasting fails to predict the heavy rain in some regions in the middle and lower reaches of Yangtze river. With the time-spatial weight probability (TSWP) neighborhood scheme, the prediction skills related to the heavy rain with CMA-GEPS are improved obviously, and the scheme reduced the occurrence of precipitation missing report. The results of precipitation probability prediction were verified by observation and Brier Scores, which show that: the TSWP neighborhood scheme is superior to the original single point ensemble probability forecast method and the control forecast, and also has a well application values for the heavy storm prediction in the Meiyu period.
Based on the Global Ensemble Prediction System in China Meteorological Administration (CMA-GEPS), the extreme Meiyu process over China in 2020 was evaluated. Results show that, during the Meiyu season, a strong and stable western Pacific subtropical high (WPSH) and a gradually strengthened East Asian summer monsoon provide favorable dynamic and moisture conditions for strong rainfall. For the western Pacific subtropical high, CMA-GEPS could skillfully forecast the evolution trend of WPSH index with 7-9 leading days; the CMA-GEPS prediction skills of WPSH strength and area are about the same level as the results from the NCEP ensemble prediction system, and the WPSH strength presents the weaker bias compared with the observation; the prediction skills of ridge line and western boundary index with CMA-GEPS are comparable with the results from ECMWF ensemble prediction system, and the forecasting bias is mainly attributed to the more southward location of ridge line and more eastward center position of western boundary. For the East Asian summer monsoon, CMA-GEPS could skillfully predict the index with 9 leading days, which was two days earlier than the control forecast. The CMA-GEPS control forecasting bias is mainly attributed to the weaker precipitation intensity and more southward location of strong rainfall belt, and also the control forecasting fails to predict the heavy rain in some regions in the middle and lower reaches of Yangtze river. With the time-spatial weight probability (TSWP) neighborhood scheme, the prediction skills related to the heavy rain with CMA-GEPS are improved obviously, and the scheme reduced the occurrence of precipitation missing report. The results of precipitation probability prediction were verified by observation and Brier Scores, which show that: the TSWP neighborhood scheme is superior to the original single point ensemble probability forecast method and the control forecast, and also has a well application values for the heavy storm prediction in the Meiyu period.
在线获得:September 15, 2022, DOI: :10.13878/j.cnki.dqkxxb. 20211121001
Abstract:
At present, a Regional Ensemble Prediction System has been developed by Kelamayi Meteorological Bureau. The system has only adopted initial condition perturbation of Ensemble Transform Kalman Filter(ETKF), and the system is lack of spread. In order to improve the skill of this Ensemble Prediction System, the model perturbation method of Stochastic Physics Parameterization Tendency(SPPT) is adopted and tested. This paper conducted sensitivity test on critical parameter of SPPT and parameter setting of SPPT is determined. Ensemble forecast experiment test is conducted and compared for both ETKF scheme and ETKF-SPPT scheme. The results show that the ETKF method can generate initial condition perturbation with dynamic structure, but the spread will saturated within short forecast lead time and will decrease due to the constraint of identical LBC for all members. With SPPT model perturbation method adopted, the ensemble spread can significantly improved. Ensemble verification scores indicate that the reliability of ETKF without model perturbation is small, and the root mean square error(RMSE) is relatively large, while add model perturbation to initial condition perturbation will improve the probabilistic forecast skill with larger forecast reliability and smaller(RMSE) . The results of gale forecast show that the adoption of model perturbation method can significantly improve the ensemble forecast that it has more accurate forecast on the magnitude and time period of local gale.
At present, a Regional Ensemble Prediction System has been developed by Kelamayi Meteorological Bureau. The system has only adopted initial condition perturbation of Ensemble Transform Kalman Filter(ETKF), and the system is lack of spread. In order to improve the skill of this Ensemble Prediction System, the model perturbation method of Stochastic Physics Parameterization Tendency(SPPT) is adopted and tested. This paper conducted sensitivity test on critical parameter of SPPT and parameter setting of SPPT is determined. Ensemble forecast experiment test is conducted and compared for both ETKF scheme and ETKF-SPPT scheme. The results show that the ETKF method can generate initial condition perturbation with dynamic structure, but the spread will saturated within short forecast lead time and will decrease due to the constraint of identical LBC for all members. With SPPT model perturbation method adopted, the ensemble spread can significantly improved. Ensemble verification scores indicate that the reliability of ETKF without model perturbation is small, and the root mean square error(RMSE) is relatively large, while add model perturbation to initial condition perturbation will improve the probabilistic forecast skill with larger forecast reliability and smaller(RMSE) . The results of gale forecast show that the adoption of model perturbation method can significantly improve the ensemble forecast that it has more accurate forecast on the magnitude and time period of local gale.
在线获得:September 07, 2022, DOI: :10.13878/j.cnki.dqkxxb. 20211228001
Abstract:
As an important part of the cryosphere, snow cover has an important impact on atmospheric circulation and the hydrologic cycle. 98% of the seasonal snow in the world is located in the northern hemisphere. Eurasia continent is the main snow area in the Northern Hemisphere. China has a vast territory with nearly 50 degrees latitude across from north to south, and snow is widely distributed, which is important for studying spatial and temporal dynamics of snow cover. This paper proposes a trend extraction method based on empirical mode decomposition (EMD) based on the Snow Cover (SNC) data of FY-3 meteorological satellite and discusses the temporal and spatial characteristics and variation trends of Snow Cover in China during the past decade (2010-2019). The results show that: 1) China"s Snow Cover Frequency (SCF) has significant seasonal characteristics, which increases first and then decreases, and reaches the maximum SCF in February and March each year. The inter-annual SCF in northeast China has a significant trend of decline, but there is little change in other regions. 2) Snow Cover Rate (SCR) in Inner Mongolia and Xinjiang has decreased by 1.6% and 1.5% in the last decade, respectively. SCR in other areas has not changed significantly. SCR in main snow covered areas changed from increase to decrease in 2016.This study is of great significance to understand the spatial and temporal dynamics of typical snow cover areas in China and to further explore the relationship between snow cover and air temperature, precipitation, and other influential factors. At the same time, relevant results are obtained from the data of the Wind Cloud Meteorological Satellite, and the application of the observation data of the FY-3 satellite is strengthened.
As an important part of the cryosphere, snow cover has an important impact on atmospheric circulation and the hydrologic cycle. 98% of the seasonal snow in the world is located in the northern hemisphere. Eurasia continent is the main snow area in the Northern Hemisphere. China has a vast territory with nearly 50 degrees latitude across from north to south, and snow is widely distributed, which is important for studying spatial and temporal dynamics of snow cover. This paper proposes a trend extraction method based on empirical mode decomposition (EMD) based on the Snow Cover (SNC) data of FY-3 meteorological satellite and discusses the temporal and spatial characteristics and variation trends of Snow Cover in China during the past decade (2010-2019). The results show that: 1) China"s Snow Cover Frequency (SCF) has significant seasonal characteristics, which increases first and then decreases, and reaches the maximum SCF in February and March each year. The inter-annual SCF in northeast China has a significant trend of decline, but there is little change in other regions. 2) Snow Cover Rate (SCR) in Inner Mongolia and Xinjiang has decreased by 1.6% and 1.5% in the last decade, respectively. SCR in other areas has not changed significantly. SCR in main snow covered areas changed from increase to decrease in 2016.This study is of great significance to understand the spatial and temporal dynamics of typical snow cover areas in China and to further explore the relationship between snow cover and air temperature, precipitation, and other influential factors. At the same time, relevant results are obtained from the data of the Wind Cloud Meteorological Satellite, and the application of the observation data of the FY-3 satellite is strengthened.
在线获得:September 01, 2022, DOI: :10.13878/j.cnki.dqkxxb. 20220623001
Abstract:
The observational stability, observational ability, and rationality of both base data and products of millimeter cloud radar (MCR for short) installed at Shanghai Meteorological Service during “The study and experiment of vertical integrated meteorological observation technology in mega-cities” (MCME for short) have been evaluated using observations from ground-based Lidar distrometer, micro-rain radar, radiosonde, FY-4A’s products as well as surface rain gage. The results show that: the observational stability of MCR is considerably high that only one-time software failure happened during the MCME and the data acquisition rate is larger than 95%. The minimal detectable reflectivity of MCR is generally distributed within -40 to -20 dBZ and has an exponential distribution in the vertical direction which fits well with the theory. The minimal detectable reflectivity of MCR changes little (smaller than 2 dB for heights lower than 9 km) during the MCME. A false “No Cloud” region will be seen in the MCR’s observation when the rain rate is larger than 4-5 mm/h. Although the raw data of the two MCRs have certain differences, the pattern of reflectivity in the time-height cross-section is highly reasonable indicated by the comparisons between the reflectivity from MCR’s observation, the reflectivity calculated with Lidar distrometer’s observation, and the reflectivity from micro-rain radar’s observation. The cloud top height and cloud base height retrieved by MCR are also evaluated by the cloud top/base height calculated by radiosonde and cloud top height retrieved by FY-4A satellite, and the results show certainly a degree of consistency among the three observations. The inconsistency of reflectivity due to the merge of multiple pulses with different pulse widths used in MCR’s base data processing and the false “clear sky area” due to the strong attenuation are two obvious issues that may have significant impacts on the operational usage of MCR. The advice on how to improve the current MCR from the perspective of the demand for the development of the Shanghai Meteorological Service has been given at the end of the paper.
The observational stability, observational ability, and rationality of both base data and products of millimeter cloud radar (MCR for short) installed at Shanghai Meteorological Service during “The study and experiment of vertical integrated meteorological observation technology in mega-cities” (MCME for short) have been evaluated using observations from ground-based Lidar distrometer, micro-rain radar, radiosonde, FY-4A’s products as well as surface rain gage. The results show that: the observational stability of MCR is considerably high that only one-time software failure happened during the MCME and the data acquisition rate is larger than 95%. The minimal detectable reflectivity of MCR is generally distributed within -40 to -20 dBZ and has an exponential distribution in the vertical direction which fits well with the theory. The minimal detectable reflectivity of MCR changes little (smaller than 2 dB for heights lower than 9 km) during the MCME. A false “No Cloud” region will be seen in the MCR’s observation when the rain rate is larger than 4-5 mm/h. Although the raw data of the two MCRs have certain differences, the pattern of reflectivity in the time-height cross-section is highly reasonable indicated by the comparisons between the reflectivity from MCR’s observation, the reflectivity calculated with Lidar distrometer’s observation, and the reflectivity from micro-rain radar’s observation. The cloud top height and cloud base height retrieved by MCR are also evaluated by the cloud top/base height calculated by radiosonde and cloud top height retrieved by FY-4A satellite, and the results show certainly a degree of consistency among the three observations. The inconsistency of reflectivity due to the merge of multiple pulses with different pulse widths used in MCR’s base data processing and the false “clear sky area” due to the strong attenuation are two obvious issues that may have significant impacts on the operational usage of MCR. The advice on how to improve the current MCR from the perspective of the demand for the development of the Shanghai Meteorological Service has been given at the end of the paper.
在线获得:July 07, 2022, DOI: :10.13878/j.cnki.dqkxxb. 20220503001
Abstract:
Based on the satellite derived snow depth over the Tibetan Plateau (TP), daily rainfall data of 261 meteorological stations in South China (SC) and the ERA5 reanalysis dataset during 1979-2018, relationships between the TP winter snow depth and precipitation during the first rainy season (FRS) in SC have been investigated. Results show that: (1) Connections between snow depth over the western TP and precipitation during the FRS in SC are the most robust and the TP snow depth mainly affects frontal precipitation of the FSR, whereas it shows less impact on summer monsoonal rainfall. (2) Onset date of the FRS in above normal TP snow years is about 20 days earlier than that in below normal snow years, leading to more rainy days, longer of the FRS and more rainfall during the FRS. However, rainfall intensity during the FRS shows small difference between different types of the TP snow years. (3) The TP is colder in above normal snow year and the cooling effect stimulates an abnormal anticyclonic circulation over the TP. However, tripole anomaly patterns of 500 hPa geopotential height occur at East Asian coastal region. Configurations of the circulation facilitate cold air in middle-high latitude regions invade SC, which makes a colder SC. And the enhanced northwest Pacific subtropical high intensifies the low-level southerly flow and water vapor supplement. The front swings northward-southward in northern part of the SC during March-April. The FRS has been established once the dry cold northerly and the warm-wet southerly flow invade the SC in early April. In below normal TP snow years, both the cold northerly and warm southerly flow are weak and inactivity and the front in northern part of the SC is interrupted in early April. When the northerly and southerly flow invades the SC in mid-to-late April, the front is reverted and the FRS occurs later.
Based on the satellite derived snow depth over the Tibetan Plateau (TP), daily rainfall data of 261 meteorological stations in South China (SC) and the ERA5 reanalysis dataset during 1979-2018, relationships between the TP winter snow depth and precipitation during the first rainy season (FRS) in SC have been investigated. Results show that: (1) Connections between snow depth over the western TP and precipitation during the FRS in SC are the most robust and the TP snow depth mainly affects frontal precipitation of the FSR, whereas it shows less impact on summer monsoonal rainfall. (2) Onset date of the FRS in above normal TP snow years is about 20 days earlier than that in below normal snow years, leading to more rainy days, longer of the FRS and more rainfall during the FRS. However, rainfall intensity during the FRS shows small difference between different types of the TP snow years. (3) The TP is colder in above normal snow year and the cooling effect stimulates an abnormal anticyclonic circulation over the TP. However, tripole anomaly patterns of 500 hPa geopotential height occur at East Asian coastal region. Configurations of the circulation facilitate cold air in middle-high latitude regions invade SC, which makes a colder SC. And the enhanced northwest Pacific subtropical high intensifies the low-level southerly flow and water vapor supplement. The front swings northward-southward in northern part of the SC during March-April. The FRS has been established once the dry cold northerly and the warm-wet southerly flow invade the SC in early April. In below normal TP snow years, both the cold northerly and warm southerly flow are weak and inactivity and the front in northern part of the SC is interrupted in early April. When the northerly and southerly flow invades the SC in mid-to-late April, the front is reverted and the FRS occurs later.
在线获得:June 22, 2022, DOI: 10.13878/j.cnki.dqkxxb.20220406001
Abstract:
The key dynamic forcing factors and sources of water vapor influencing the remote heavy rainfall over North China produced by Typhoon Lekima on 10 August 2019 are investigated using the surface rain gauge data, ERA5 reanalysis data, and ECWMF ensemble forecasts data. Ensemble sensitivity analysis shows that low-level relative vorticity over the remote typhoon precipitation (TRP) area is the most significant dynamic factor facilitating TRP. The stronger low-level relative vorticity is closely associated with the enhancement of northerly winds in the north caused by the deepening of the low-level short-wave trough and jointly related to the strengthening low-level southerly winds between the TRP and typhoon precipitation (TP) area. The divergence term of relative vorticity is the crucial dynamic process that dominates the strengthening and weakening period of TRP. During the TRP enhancement phase, the positive vorticity is mainly contributed by the positive divergence term, while the negative divergence term leads to the decrease of relative vorticity and the weakening of TRP intensity. The water vapor in the TRP region at 500 hPa is mainly contributed by local area and Typhoon Lekima, while 60% of the water vapor at 700 hPa is contributed by Typhoon Lekima. 40% of the water vapor at 850 hPa is contributed by Typhoon Rosa, and the remaining 60% of water vapor is transported from Typhoon Lekima and the local area.
The key dynamic forcing factors and sources of water vapor influencing the remote heavy rainfall over North China produced by Typhoon Lekima on 10 August 2019 are investigated using the surface rain gauge data, ERA5 reanalysis data, and ECWMF ensemble forecasts data. Ensemble sensitivity analysis shows that low-level relative vorticity over the remote typhoon precipitation (TRP) area is the most significant dynamic factor facilitating TRP. The stronger low-level relative vorticity is closely associated with the enhancement of northerly winds in the north caused by the deepening of the low-level short-wave trough and jointly related to the strengthening low-level southerly winds between the TRP and typhoon precipitation (TP) area. The divergence term of relative vorticity is the crucial dynamic process that dominates the strengthening and weakening period of TRP. During the TRP enhancement phase, the positive vorticity is mainly contributed by the positive divergence term, while the negative divergence term leads to the decrease of relative vorticity and the weakening of TRP intensity. The water vapor in the TRP region at 500 hPa is mainly contributed by local area and Typhoon Lekima, while 60% of the water vapor at 700 hPa is contributed by Typhoon Lekima. 40% of the water vapor at 850 hPa is contributed by Typhoon Rosa, and the remaining 60% of water vapor is transported from Typhoon Lekima and the local area.
在线获得:June 06, 2022, DOI: 10.13878/j.cnki.dqkxxb.20220215001
Abstract:
In recent years, O3 pollution in Nanjing has gradually intensified. In order to understand the impact of surrounding cities on O3 in Nanjing, we simulated the air quality in the Yangtze River Delta(YRD) using the source-oriented WRF/CMAQ regional air quality model from March to October 2018.By tracking the emissions from 41 cities in the YRD and outside the YRD, the characteristics of the transportation of O3 in Nanjing were analyzed under different winds. The results show that from March to October 2018, Nanjing contributes 56.8% of local O3 on polluted days, and contributed 49.5% on polluted days. When pollution occurs, the contribution of surrounding cities to Nanjing increased from 36.4% to 46.3%, and the contribution from outside the YRD to Nanjing decreased from 6.8% to 4.7%. From the perspective of daily changes, Nanjing O3 accounts for more than 70% of the local contribution during the daytime, and at night, most of the transport contributions come from surrounding cities and areas outside the YRD (more than 95%) .On all O3 pollution days, the contribution in Jiangsu Province accounts for 73.1%, 10.8% in Zhejiang Province, 10.5% in Anhui Province and 0.95% in Shanghai. During the pollution period, the contribution ratio of O3 (O3N) produced by NOx as a precursor in Nanjing to O3 (O3V) produced by VOCs as a precursor was about 7:13; During all polluting periods, the proportion of southeast and northeast winds was 38.0% and 35.9% respectively, when the dominant wind direction is northeast, Nanjing has the highest concentration of non-background O3, and the contribution of upwind to Yangzhou reached 13.6%. When the dominant wind direction is southeast wind, the upwind to Changzhou (7.3%), Zhenjiang (7.0%) and Wuxi (6.5%) contributed more to Nanjing O3. Therefore, Nanjing O3 pollution control should consider the transportation of upwind to cities.
In recent years, O3 pollution in Nanjing has gradually intensified. In order to understand the impact of surrounding cities on O3 in Nanjing, we simulated the air quality in the Yangtze River Delta(YRD) using the source-oriented WRF/CMAQ regional air quality model from March to October 2018.By tracking the emissions from 41 cities in the YRD and outside the YRD, the characteristics of the transportation of O3 in Nanjing were analyzed under different winds. The results show that from March to October 2018, Nanjing contributes 56.8% of local O3 on polluted days, and contributed 49.5% on polluted days. When pollution occurs, the contribution of surrounding cities to Nanjing increased from 36.4% to 46.3%, and the contribution from outside the YRD to Nanjing decreased from 6.8% to 4.7%. From the perspective of daily changes, Nanjing O3 accounts for more than 70% of the local contribution during the daytime, and at night, most of the transport contributions come from surrounding cities and areas outside the YRD (more than 95%) .On all O3 pollution days, the contribution in Jiangsu Province accounts for 73.1%, 10.8% in Zhejiang Province, 10.5% in Anhui Province and 0.95% in Shanghai. During the pollution period, the contribution ratio of O3 (O3N) produced by NOx as a precursor in Nanjing to O3 (O3V) produced by VOCs as a precursor was about 7:13; During all polluting periods, the proportion of southeast and northeast winds was 38.0% and 35.9% respectively, when the dominant wind direction is northeast, Nanjing has the highest concentration of non-background O3, and the contribution of upwind to Yangzhou reached 13.6%. When the dominant wind direction is southeast wind, the upwind to Changzhou (7.3%), Zhenjiang (7.0%) and Wuxi (6.5%) contributed more to Nanjing O3. Therefore, Nanjing O3 pollution control should consider the transportation of upwind to cities.
在线获得:June 02, 2022, DOI: 10.13878/j.cnki.dqkxxb.20210811002
Abstract:
Based on the daily precipitation of 24 global climate models from the sixth phase of the Coupled Model Intercomparison Project 6 (CMIP6) multimodel simulations, the generalized extreme value distribution (GEV) is introduced to study the risks of precipitation extremes that expected to occur every 20, 50 and 100 years over China under 1.5/2°C global warming. Compared to the historical period (1995-2014), the changes in the probability risks of extreme precipitation under global warming of 1.5/2℃ present an overall increasing trend. Although their spatial distributions show similar characteristics, the additional half a degree global warming will lead to a higher risk. For example, extreme precipitation that occurred once every 50 years will become once about every 17/14years under the warming of 1.5/2°C, respectively, and extreme precipitation will become more frequent. There are regional differences in the responses of different regions to climate warming, among which the middle and upper reaches of the Yangtze and Yellow Rivers and the Qinghai-Tibet Plateau region in the Western China, and the middle and lower reaches of Yangtze and Yellow Rivers and its south in Eastern China, are highly sensitive response regions to climate change, and their probability ratios reach 3 or even 5 or more. Furthermore, the influence and contribution measures of location and scale parameters on the probability ratios are explored from a theoretical perspective based on the probability distributions, and are used to explore the influences of the climate means and variability changes on the risks of extreme precipitation. The results show that there are significant differences between Eastern China and Western China in the incremental changes of location and scale parameters, and in the rates of probability risk changes, which lead to differences of the factors that influencing the risk of extreme precipitation. In the Western China, although the changes in climate means and variabilities of extreme precipitation are small, the probability ratios increase significantly due to the high rates of probability risk changes. In contrast, the change rates are small, but the climate means and variabilities present a high increase, which also lead to an increase in the Eastern China. Moreover, compared to the location parameters, the increase risks in most of regions over China are mainly due to the changes of scale parameters of extreme precipitation in the future.
Based on the daily precipitation of 24 global climate models from the sixth phase of the Coupled Model Intercomparison Project 6 (CMIP6) multimodel simulations, the generalized extreme value distribution (GEV) is introduced to study the risks of precipitation extremes that expected to occur every 20, 50 and 100 years over China under 1.5/2°C global warming. Compared to the historical period (1995-2014), the changes in the probability risks of extreme precipitation under global warming of 1.5/2℃ present an overall increasing trend. Although their spatial distributions show similar characteristics, the additional half a degree global warming will lead to a higher risk. For example, extreme precipitation that occurred once every 50 years will become once about every 17/14years under the warming of 1.5/2°C, respectively, and extreme precipitation will become more frequent. There are regional differences in the responses of different regions to climate warming, among which the middle and upper reaches of the Yangtze and Yellow Rivers and the Qinghai-Tibet Plateau region in the Western China, and the middle and lower reaches of Yangtze and Yellow Rivers and its south in Eastern China, are highly sensitive response regions to climate change, and their probability ratios reach 3 or even 5 or more. Furthermore, the influence and contribution measures of location and scale parameters on the probability ratios are explored from a theoretical perspective based on the probability distributions, and are used to explore the influences of the climate means and variability changes on the risks of extreme precipitation. The results show that there are significant differences between Eastern China and Western China in the incremental changes of location and scale parameters, and in the rates of probability risk changes, which lead to differences of the factors that influencing the risk of extreme precipitation. In the Western China, although the changes in climate means and variabilities of extreme precipitation are small, the probability ratios increase significantly due to the high rates of probability risk changes. In contrast, the change rates are small, but the climate means and variabilities present a high increase, which also lead to an increase in the Eastern China. Moreover, compared to the location parameters, the increase risks in most of regions over China are mainly due to the changes of scale parameters of extreme precipitation in the future.
在线获得:May 23, 2022, DOI: :10.13878/j.cnki.dqkxxb. 20220503002
Abstract:
A wind profiler radar is a new type of Doppler wind radar designed to measure the horizontal wind vectors, and are able to provide wind profiles at various elevations with high temporal and spatial resolution. It plays an increasingly important role in China"s Meteorological business. However, the quality of wind profiler radar data varies widely consider-ing the different types of radars deployed in China. To better utilize these data in numerical weather prediction (NWP), this study assesses the data quality from five different types of wind profiler radars (i.e., CFL-06, GLC-24, TWP8-L, CFL-03 and CLC-11-D) at 20 stations in North China from June to September 2019. Results show that each type of profiler has strong detection ability, but different profilers have great differences in data acquisition rate and effective detection height. Without considering the influence of precipitation, the data quality of v-wind is better than that of u-wind for all types of profilers. In all air conditions, the quality of u-wind data from TWP8-L profiler is relatively the best, followed by CFL-03 radar, the quality of u-wind data from GLC-24 radar is the worst. The differences in v-wind data is not noticea-ble, while bias correction and quality control are necessary for u-wind data. The data quality of wind profile radar is quite sensitive to precipitation, which reduces the data acquisition rates at low levels and increases the data acquisition rates at the middle and high levels, with the maximum increase of 53%. The statistical results indicate precipitation is responsible for the large mean errors and root mean square errors (RMSEs) of u wind data. GLC-24 and CLC-11-D profilers are the most sensitive to precipitation. The RMSEs are increased by 5.5 m/s in precipitation regions as compared to non-precipitation regions. The u-wind and v-wind data in precipitation regions requires further quality control procedure.
A wind profiler radar is a new type of Doppler wind radar designed to measure the horizontal wind vectors, and are able to provide wind profiles at various elevations with high temporal and spatial resolution. It plays an increasingly important role in China"s Meteorological business. However, the quality of wind profiler radar data varies widely consider-ing the different types of radars deployed in China. To better utilize these data in numerical weather prediction (NWP), this study assesses the data quality from five different types of wind profiler radars (i.e., CFL-06, GLC-24, TWP8-L, CFL-03 and CLC-11-D) at 20 stations in North China from June to September 2019. Results show that each type of profiler has strong detection ability, but different profilers have great differences in data acquisition rate and effective detection height. Without considering the influence of precipitation, the data quality of v-wind is better than that of u-wind for all types of profilers. In all air conditions, the quality of u-wind data from TWP8-L profiler is relatively the best, followed by CFL-03 radar, the quality of u-wind data from GLC-24 radar is the worst. The differences in v-wind data is not noticea-ble, while bias correction and quality control are necessary for u-wind data. The data quality of wind profile radar is quite sensitive to precipitation, which reduces the data acquisition rates at low levels and increases the data acquisition rates at the middle and high levels, with the maximum increase of 53%. The statistical results indicate precipitation is responsible for the large mean errors and root mean square errors (RMSEs) of u wind data. GLC-24 and CLC-11-D profilers are the most sensitive to precipitation. The RMSEs are increased by 5.5 m/s in precipitation regions as compared to non-precipitation regions. The u-wind and v-wind data in precipitation regions requires further quality control procedure.
在线获得:May 06, 2022, DOI: :10.13878/j.cnki.dqkxxb. 20220207001
Abstract:
We proposed a novel method to predict the meteorological risk for important events, and successfully applied it to the 70th anniversary celebration of the People"s Republic of China. The method based on fine meteorological factors analysis, considered risk resources(weather risk) and vulnerability(impact on events), so that efficient measures can be taken in advance to make sure the success of the events. A risk matrix method was used to perform the analysis and prediction. Meteorological risk levels were evaluated and risk maps were drawn of major celebration events based on the investigation and analysis of meteorological factors that may affected the successful holding of the celebration events and the occurrence ratio of different meteorological events. For the 70th anniversary celebration of the People"s Republic of China, we recognized the major weather risks (from high to low) were precipitation/overcast and rain, day force eight wind, frog-haze, night force eight wind, high temperature and direct sunlight, thunder and lightning, low temperature, etc.. Risk control measures and countermeasures were put forward to the risk caused by different meteorological factors, which provided important reference for the scientific formulation and implementation of safety work plan and the successful development of activities. In the meteorological support work of major activities, a major change has been realized from considering only the occurrence probability of high impact weather to risk assessment based on weather impact and we got a good service effect for the events.
We proposed a novel method to predict the meteorological risk for important events, and successfully applied it to the 70th anniversary celebration of the People"s Republic of China. The method based on fine meteorological factors analysis, considered risk resources(weather risk) and vulnerability(impact on events), so that efficient measures can be taken in advance to make sure the success of the events. A risk matrix method was used to perform the analysis and prediction. Meteorological risk levels were evaluated and risk maps were drawn of major celebration events based on the investigation and analysis of meteorological factors that may affected the successful holding of the celebration events and the occurrence ratio of different meteorological events. For the 70th anniversary celebration of the People"s Republic of China, we recognized the major weather risks (from high to low) were precipitation/overcast and rain, day force eight wind, frog-haze, night force eight wind, high temperature and direct sunlight, thunder and lightning, low temperature, etc.. Risk control measures and countermeasures were put forward to the risk caused by different meteorological factors, which provided important reference for the scientific formulation and implementation of safety work plan and the successful development of activities. In the meteorological support work of major activities, a major change has been realized from considering only the occurrence probability of high impact weather to risk assessment based on weather impact and we got a good service effect for the events.
在线获得:May 06, 2022, DOI: :10.13878/j.cnki.dqkxxb. 20211230001
Abstract:
Nowadays, ensemble forecasting has become the main support for operational weather forecasting. However, due to the limitations and imperfections of the numerical model itself, the forecast results are generally systematically biased. In addition, different forecasting models usually have different physical parameterization schemes, initial conditions, etc., resulting in different forecasting capabilities. Therefore, how to eliminate systematic biases and how to make full and effective use of forecast information from different models to obtain more accurate weather forecasts has received extensive attention. In recent years, using statistical theory and forecasting diagnosis, multimodel ensemble forecasting technologies based on multiple ensemble prediction systems have been rapidly developed to effectively eliminate systematic biases and improve weather forecasting skills. For the three most basic surface meteorological variables (i.e., temperature, precipitation, wind), the widely used multimodel ensemble technologies such as ensemble mean (EM), bias-removed ensemble mean (BREM), superensemble (SUP), Bayesian model averaging(BMA), and ensemble model output statistics(EMOS) are first introduced from the perspective of deterministic forecasting and probabilistic forecasting. Finally, the issues that need to be paid attention to when using and developing multimodel ensemble technologies are discussed, including the consideration the number of participating models, the development of categorized precipitation and wind speed forecast models. Meanwhile, the combination of multimodel ensemble with machine learning deserves more investigation.
Nowadays, ensemble forecasting has become the main support for operational weather forecasting. However, due to the limitations and imperfections of the numerical model itself, the forecast results are generally systematically biased. In addition, different forecasting models usually have different physical parameterization schemes, initial conditions, etc., resulting in different forecasting capabilities. Therefore, how to eliminate systematic biases and how to make full and effective use of forecast information from different models to obtain more accurate weather forecasts has received extensive attention. In recent years, using statistical theory and forecasting diagnosis, multimodel ensemble forecasting technologies based on multiple ensemble prediction systems have been rapidly developed to effectively eliminate systematic biases and improve weather forecasting skills. For the three most basic surface meteorological variables (i.e., temperature, precipitation, wind), the widely used multimodel ensemble technologies such as ensemble mean (EM), bias-removed ensemble mean (BREM), superensemble (SUP), Bayesian model averaging(BMA), and ensemble model output statistics(EMOS) are first introduced from the perspective of deterministic forecasting and probabilistic forecasting. Finally, the issues that need to be paid attention to when using and developing multimodel ensemble technologies are discussed, including the consideration the number of participating models, the development of categorized precipitation and wind speed forecast models. Meanwhile, the combination of multimodel ensemble with machine learning deserves more investigation.
在线获得:March 23, 2022, DOI: 10.13878/j.cnki.dqkxxb. 20211229001
Abstract:
To study the differences and similarities between fine observation and conventional observation in fog microstructure, a systematic field observation of fog was conducted and lasted 58 days in Donghai, Lianyungang during the winter of 2020. Two fog monitors with different frequencies (5Hz and 1Hz) were applied simultaneously for measuring a radiation fog on December 28, 2020. Based on this observation, we found that compared with the 1Hz data, the 5Hz measurement observed more extreme values. In terms of the whole fog process, the results of the 5Hz fog droplet spectrometer averaged into 1Hz are less similar to the original results of 1Hz in the fog generation and dissipation stages, and more similar in the fog maturation and development stages. In terms of the spectral patterns, the spectral patterns of 5 Hz and 1 Hz are similar, while the main differences appear at the peak. The measurements of 5 Hz and 1 Hz can both reflect the relationship between the microphysics at different stages of this fog process, and the main differences appear at the fog generation stage. This may be due to the relatively small number of activation and condensation growth of new fog droplets observed at 5Hz at this stage.
To study the differences and similarities between fine observation and conventional observation in fog microstructure, a systematic field observation of fog was conducted and lasted 58 days in Donghai, Lianyungang during the winter of 2020. Two fog monitors with different frequencies (5Hz and 1Hz) were applied simultaneously for measuring a radiation fog on December 28, 2020. Based on this observation, we found that compared with the 1Hz data, the 5Hz measurement observed more extreme values. In terms of the whole fog process, the results of the 5Hz fog droplet spectrometer averaged into 1Hz are less similar to the original results of 1Hz in the fog generation and dissipation stages, and more similar in the fog maturation and development stages. In terms of the spectral patterns, the spectral patterns of 5 Hz and 1 Hz are similar, while the main differences appear at the peak. The measurements of 5 Hz and 1 Hz can both reflect the relationship between the microphysics at different stages of this fog process, and the main differences appear at the fog generation stage. This may be due to the relatively small number of activation and condensation growth of new fog droplets observed at 5Hz at this stage.
Accounting the carbon sequestration rate of terrestrial ecosystems: methods, progress and challenges
在线获得:March 14, 2022, DOI: 10.13878/j.cnki.dqkxxb. 20220303002
Abstract:
Global warming, caused by the rapid increase of atmospheric CO2 has become an urgent problem for sustainable development of human beings. Terrestrial ecosystems have played an important carbon sink role in the past decades by absorbing about 30% of the CO2 emitted by human activities. This paper reviewed the estimation methods of carbon sequestration rate of terrestrial ecosystems, including sampling inventory, flux monitoring, model simulation, remote sensing, etc., and analyzed the progresses and challenges of the current approaches for accounting terrestrial carbon sequestration. Sampling inventory and flux observations can provide direct measurement of plot-scale carbon sequestration rate, but there are many problems, such as limited observation samples and insufficient spatial representation. Model simulation methods can describe the terrestrial carbon cycles and simulate the state and change of carbon sequestration rates in terrestrial ecosystems. However, the approximating and simplifying processes in model, together with the uncertainties introduced by model-driven data, it is very challenging to accurately modeling the carbon sequestration rate of terrestrial ecosystems. Satellite remote sensing, holding the advantages of global coverage, fine resolution, and time-series observations, combined with machine learning methods, can provide a new approach for the estimation of the carbon sequestration rate of terrestrial ecosystems. So far, various accounting methods for carbon sequestration rates have not yet met the needs of monitoring carbon sequestration in terrestrial ecosystems due to the high spatial and temporal heterogeneity. In the future, it is extremely important to integrate various accounting approaches, such as ground observations, model simulations, and satellite remote sensing, to provide accurate estimation of terrestrial ecosystem carbon sinks at the regional and global scales.
Global warming, caused by the rapid increase of atmospheric CO2 has become an urgent problem for sustainable development of human beings. Terrestrial ecosystems have played an important carbon sink role in the past decades by absorbing about 30% of the CO2 emitted by human activities. This paper reviewed the estimation methods of carbon sequestration rate of terrestrial ecosystems, including sampling inventory, flux monitoring, model simulation, remote sensing, etc., and analyzed the progresses and challenges of the current approaches for accounting terrestrial carbon sequestration. Sampling inventory and flux observations can provide direct measurement of plot-scale carbon sequestration rate, but there are many problems, such as limited observation samples and insufficient spatial representation. Model simulation methods can describe the terrestrial carbon cycles and simulate the state and change of carbon sequestration rates in terrestrial ecosystems. However, the approximating and simplifying processes in model, together with the uncertainties introduced by model-driven data, it is very challenging to accurately modeling the carbon sequestration rate of terrestrial ecosystems. Satellite remote sensing, holding the advantages of global coverage, fine resolution, and time-series observations, combined with machine learning methods, can provide a new approach for the estimation of the carbon sequestration rate of terrestrial ecosystems. So far, various accounting methods for carbon sequestration rates have not yet met the needs of monitoring carbon sequestration in terrestrial ecosystems due to the high spatial and temporal heterogeneity. In the future, it is extremely important to integrate various accounting approaches, such as ground observations, model simulations, and satellite remote sensing, to provide accurate estimation of terrestrial ecosystem carbon sinks at the regional and global scales.
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2022,45(2): 280-291, DOI: 10.13878/j.cnki.dqkxxb.20200719017
Abstract:
Based on the sea surface temperature (SST) data from NOAA in USA, the asymmetric characteristics of interannual relationship between ENSO and Victoria mode (VM;EOF2 of North Pacific SST anomalies in winter (DJF)) were emphatically analyzed.Results show that the correlation between VM and ENSO is weak on the decadal scale, but strong on the interannual scale.VM has significant negative correlation with ENSO in the same year, and has strong positive correlation with ENSO in the following year.However, there is a certain asymmetry in the relationship between the positive/negative VM events and ENSO warm/cold phases on the interannual scale.The relationship between the positive VM events and the SST anomalies in the tropical central and eastern Pacific in the same winter is weak, but El Niño events often occur in the following year.In contrast, the negative VM events are usually accompanied by El Niño events in the same years, but there is no significant relationship between the negative VM events and the SST anomalies in the tropical central and eastern Pacific in the following winter and there are few ENSO events.It can be seen that the positive VM event seems to promote the occurrence and development of El Niño in the next year and can be used as one of the early prediction factors of ENSO, while the negative VM event cannot be used as the early prediction factor of ENSO.
Based on the sea surface temperature (SST) data from NOAA in USA, the asymmetric characteristics of interannual relationship between ENSO and Victoria mode (VM;EOF2 of North Pacific SST anomalies in winter (DJF)) were emphatically analyzed.Results show that the correlation between VM and ENSO is weak on the decadal scale, but strong on the interannual scale.VM has significant negative correlation with ENSO in the same year, and has strong positive correlation with ENSO in the following year.However, there is a certain asymmetry in the relationship between the positive/negative VM events and ENSO warm/cold phases on the interannual scale.The relationship between the positive VM events and the SST anomalies in the tropical central and eastern Pacific in the same winter is weak, but El Niño events often occur in the following year.In contrast, the negative VM events are usually accompanied by El Niño events in the same years, but there is no significant relationship between the negative VM events and the SST anomalies in the tropical central and eastern Pacific in the following winter and there are few ENSO events.It can be seen that the positive VM event seems to promote the occurrence and development of El Niño in the next year and can be used as one of the early prediction factors of ENSO, while the negative VM event cannot be used as the early prediction factor of ENSO.
2014,37(5): 642-652, DOI: 10.13878/j.cnki.dqkxxb.20121017006
Abstract:
In this paper,the Weather Research and Forecast Model(WRF) is coupled with Surface-Layer Scheme,Single-Layer Urban Canopy Model and Mingle-Layer Urban Canopy Model respectively to evaluate the simulation effect of various parameterizations on the weather conditions on 1 August 2007 in Nanjing.The best urban parameterization scheme is coupled into WRF to study the impact of land cover change on the Urban Heat Island(UHI) effect in Nanjing.Results show that the Mingle-Layer Urban Canopy Model shows the best simulation effect for surface temperature and 10m wind field.Urbanization makes surface air temperature increase over the region,especially at night and thus intensifies the UHI effect.After urbanization,the wind speed in the downtown area decreases obviously while the Urban Heat Circulation occurs more apparently.There also exists the downstream effect of UHI in Nanjing.
In this paper,the Weather Research and Forecast Model(WRF) is coupled with Surface-Layer Scheme,Single-Layer Urban Canopy Model and Mingle-Layer Urban Canopy Model respectively to evaluate the simulation effect of various parameterizations on the weather conditions on 1 August 2007 in Nanjing.The best urban parameterization scheme is coupled into WRF to study the impact of land cover change on the Urban Heat Island(UHI) effect in Nanjing.Results show that the Mingle-Layer Urban Canopy Model shows the best simulation effect for surface temperature and 10m wind field.Urbanization makes surface air temperature increase over the region,especially at night and thus intensifies the UHI effect.After urbanization,the wind speed in the downtown area decreases obviously while the Urban Heat Circulation occurs more apparently.There also exists the downstream effect of UHI in Nanjing.
Abstract:
Based on the multiple type observational data,this paper preliminarily analyses the meso scale convective systems(MCSs) and weather background producing an extremely heavy rain along the Mei yu front in Hubei and Anhui provinces during 29—30 June 2009,and investigates the multi scale structure features of the Mei yu frontal rainstorm system.Then the meso scale numerical model WRF with large domain and 9 km horizontal resolution is used to carry out a 3 domain nested fine simulation for the heavy rain process.Morlet wavelet transformation is carried out to do spatial band passing filter for the model outputs,and the meso 〖WTBX〗α, β〖WTB1〗 and 〖WTBX〗γ〖WTB1〗 scale systems are separated out,in such a way that the three dimensional spatial dynamic and thermodynamic characteristics of the meso scale systems with different scales are studied.The results are as follows.The extremely Mei yu frontal heavy rain is directly resulted from several MCSs with different scales,which are of different features on satellite cloud images and radar echoes.On meso 〖WTBX〗α, β〖WTB1〗 and 〖WTBX〗γ〖WTB1〗 scales,the Mei yu frontal heavy rain system has obvious different dynamic and thermodynamic structure features in horizontal and vertical directions.The meso 〖WTBX〗α〖WTB1〗 and 〖WTBX〗β〖WTB1〗 scale systems have obvious vertical circulation,while meso 〖WTBX〗γ〖WTB1〗 scale system has some features of inertial gravity waves and usually develops in meso 〖WTBX〗α〖WTB1〗 and 〖WTBX〗β〖WTB1〗 scale system.Lastly,a physic conceptual model is advanced for the typical Mei yu frontal rainstorm system.
Based on the multiple type observational data,this paper preliminarily analyses the meso scale convective systems(MCSs) and weather background producing an extremely heavy rain along the Mei yu front in Hubei and Anhui provinces during 29—30 June 2009,and investigates the multi scale structure features of the Mei yu frontal rainstorm system.Then the meso scale numerical model WRF with large domain and 9 km horizontal resolution is used to carry out a 3 domain nested fine simulation for the heavy rain process.Morlet wavelet transformation is carried out to do spatial band passing filter for the model outputs,and the meso 〖WTBX〗α, β〖WTB1〗 and 〖WTBX〗γ〖WTB1〗 scale systems are separated out,in such a way that the three dimensional spatial dynamic and thermodynamic characteristics of the meso scale systems with different scales are studied.The results are as follows.The extremely Mei yu frontal heavy rain is directly resulted from several MCSs with different scales,which are of different features on satellite cloud images and radar echoes.On meso 〖WTBX〗α, β〖WTB1〗 and 〖WTBX〗γ〖WTB1〗 scales,the Mei yu frontal heavy rain system has obvious different dynamic and thermodynamic structure features in horizontal and vertical directions.The meso 〖WTBX〗α〖WTB1〗 and 〖WTBX〗β〖WTB1〗 scale systems have obvious vertical circulation,while meso 〖WTBX〗γ〖WTB1〗 scale system has some features of inertial gravity waves and usually develops in meso 〖WTBX〗α〖WTB1〗 and 〖WTBX〗β〖WTB1〗 scale system.Lastly,a physic conceptual model is advanced for the typical Mei yu frontal rainstorm system.
2019,42(4): 631-640, DOI: 10.13878/j.cnki.dqkxxb.20170815015
Abstract:
Imperative quality control methods for Doppler radar data,such as ground clutter elimination,range folding elimination and velocity dealiasing,should be adopted before being used for quantitative analyses,due to the serious impacts originating from certain non-meteorological factors.In this study,in order to precisely identify the ground clutter and precipitous echo,an automatic algorithm based on the Support Vector Machine(SVM) is performed,based on the observational CINRAD/SA Doppler weather radar data in the areas of Anqing and Changzhou from June to August,2013,and the results are compared with the recognition effect based on the Artificial Neural Networks(ANNs) method.Statistical learning theory(SLT) is favorable for small samples,which focuses on the statistical law and nature of small-sample learning.As a new machine learning based on SLT,the basic principle of the SVM is to possess an optimal separating hyperplane which is able to satisfy the requirement of the classification accuracy by introducing the largest classification intervals on either side of the hyperplane.In the first step,the dataset used in the experiment will be establised by empirically distinguishing the ground clutter and precipitous points at each bin.Next,several characteristic parameters,which are used to quantify the possibility affected by the ground clutter,such as reflectivity vertical variation (GDBZ),reflectivity horizontal texture (TDBZ),velocity regional average (MDVE),and spectrum regional average (MDSW),will be derived from the reflectivity,radaial velocity,spectrum width and spatial variance information of the ground clutter and precipitous echo.The statistical results of the above characteristic parameters show the following:a large portion of these parameters vary in terms of ground clutter and precipitous echo,which indicates that the seven parameters (GDBZ,TDBZ,SPIN,SIGN,MDVE,MDSW and SDVE) contribute to the identifiable recognition of the ground clutter and precipitous echo.Based on the above conclusions,seven parameters,which are regarded as the trigger (the training factor of SVM) to establish the SVM's training model,can be randomly extracted from the database.Finally,the training model is used to automatically recognize the ground clutter and precipitation using the random data from the database.The recognition effect of the SVM method will be examined by comparing the model output with the empirical identifications,and the examination of the ANNs algorithm is the same as that of the SVM method.The comparison of the recognition effect between the SVM and ANNs methods reveals the following:(1) The statistically identifiable recognition parameter for the sSVM and ANNs methods appears to be steady,despite the fact that the Doppler radar data vary in shape and position between Anqing and Changzhou;(2) An identifying threshold must be determined for the ANNs method before the ground clutter and precipitous echo are identified,which will lead to a differently identifiable accuracy with the unlike threshold;and (3) Overall,the SVM method works better than the ANNs method in terms of radar echo identification.Moreover,the identifiable recognition accuracy of the latter increases significantly with the increasing total number of training samples,while the identifiable recognition accuracy of the former performs at a highly accurate level,which remains relatively stable with the changes in the training samples.In terms of the identification accuracy of the total samples (ground clutter and precipitous echo) and identification accuracy of the ground clutter echo,the SVM method presents better results than the ANNs method.As for the precipitous echo erroneous recognition,the ANNs method performs slightly better than the SVM,but both methods control the erroneous recognition rate at a low level.
Imperative quality control methods for Doppler radar data,such as ground clutter elimination,range folding elimination and velocity dealiasing,should be adopted before being used for quantitative analyses,due to the serious impacts originating from certain non-meteorological factors.In this study,in order to precisely identify the ground clutter and precipitous echo,an automatic algorithm based on the Support Vector Machine(SVM) is performed,based on the observational CINRAD/SA Doppler weather radar data in the areas of Anqing and Changzhou from June to August,2013,and the results are compared with the recognition effect based on the Artificial Neural Networks(ANNs) method.Statistical learning theory(SLT) is favorable for small samples,which focuses on the statistical law and nature of small-sample learning.As a new machine learning based on SLT,the basic principle of the SVM is to possess an optimal separating hyperplane which is able to satisfy the requirement of the classification accuracy by introducing the largest classification intervals on either side of the hyperplane.In the first step,the dataset used in the experiment will be establised by empirically distinguishing the ground clutter and precipitous points at each bin.Next,several characteristic parameters,which are used to quantify the possibility affected by the ground clutter,such as reflectivity vertical variation (GDBZ),reflectivity horizontal texture (TDBZ),velocity regional average (MDVE),and spectrum regional average (MDSW),will be derived from the reflectivity,radaial velocity,spectrum width and spatial variance information of the ground clutter and precipitous echo.The statistical results of the above characteristic parameters show the following:a large portion of these parameters vary in terms of ground clutter and precipitous echo,which indicates that the seven parameters (GDBZ,TDBZ,SPIN,SIGN,MDVE,MDSW and SDVE) contribute to the identifiable recognition of the ground clutter and precipitous echo.Based on the above conclusions,seven parameters,which are regarded as the trigger (the training factor of SVM) to establish the SVM's training model,can be randomly extracted from the database.Finally,the training model is used to automatically recognize the ground clutter and precipitation using the random data from the database.The recognition effect of the SVM method will be examined by comparing the model output with the empirical identifications,and the examination of the ANNs algorithm is the same as that of the SVM method.The comparison of the recognition effect between the SVM and ANNs methods reveals the following:(1) The statistically identifiable recognition parameter for the sSVM and ANNs methods appears to be steady,despite the fact that the Doppler radar data vary in shape and position between Anqing and Changzhou;(2) An identifying threshold must be determined for the ANNs method before the ground clutter and precipitous echo are identified,which will lead to a differently identifiable accuracy with the unlike threshold;and (3) Overall,the SVM method works better than the ANNs method in terms of radar echo identification.Moreover,the identifiable recognition accuracy of the latter increases significantly with the increasing total number of training samples,while the identifiable recognition accuracy of the former performs at a highly accurate level,which remains relatively stable with the changes in the training samples.In terms of the identification accuracy of the total samples (ground clutter and precipitous echo) and identification accuracy of the ground clutter echo,the SVM method presents better results than the ANNs method.As for the precipitous echo erroneous recognition,the ANNs method performs slightly better than the SVM,but both methods control the erroneous recognition rate at a low level.
2023,46(3): 332-344, DOI: 10.13878/j.cnki.dqkxxb.20230303001
Abstract:
The summer of 2022 exhibits significant characteristics of high temperature,low humidity,and rainfall in South China.Previous studies have focused on extreme events of high temperature and low rainfall in summer,whereas attention to near-ground relative humidity,which is closely related to human comfort and crop growth,has been relatively insufficient.In this study,we define events of positive temperature anomaly,negative precipitation anomaly,and negative relative humidity anomaly exceeding one time of the interannual standard deviation between 1959 and 2022 are as compound events of summer high temperature,low humidity,and rainfall.Monthly ERA5 atmospheric reanalysis data of 1959—2022 are used in this study.We study the effect of spring soil moisture on the compound events in summer by composite analysis and a dynamic adjustment approach based on constructed circulation analogs,and the physical mechanism is analyzed.The results show that:1) The hot spots of the coupling between spring soil moisture and summer climate in south China are basically consistent with the high variability of summer temperature,precipitation,and relative humidity in 2022.2) When the soil in the Yangtze River Basin and Huang-Huai area is dry in spring and the southeast area is wet,the compound events of drying and heat will occur in summer.3) The effect of spring soil moisture on summer climate variability is mainly realized by adjusting the distribution of local evapotranspiration and net radiation energy.The study of the compound extreme events of high temperature,low humidity,and rainfall is of great significance in effectively preventing all kinds of disasters and safety accidents caused by them,protecting people's lives and property,and maintaining social production order.
The summer of 2022 exhibits significant characteristics of high temperature,low humidity,and rainfall in South China.Previous studies have focused on extreme events of high temperature and low rainfall in summer,whereas attention to near-ground relative humidity,which is closely related to human comfort and crop growth,has been relatively insufficient.In this study,we define events of positive temperature anomaly,negative precipitation anomaly,and negative relative humidity anomaly exceeding one time of the interannual standard deviation between 1959 and 2022 are as compound events of summer high temperature,low humidity,and rainfall.Monthly ERA5 atmospheric reanalysis data of 1959—2022 are used in this study.We study the effect of spring soil moisture on the compound events in summer by composite analysis and a dynamic adjustment approach based on constructed circulation analogs,and the physical mechanism is analyzed.The results show that:1) The hot spots of the coupling between spring soil moisture and summer climate in south China are basically consistent with the high variability of summer temperature,precipitation,and relative humidity in 2022.2) When the soil in the Yangtze River Basin and Huang-Huai area is dry in spring and the southeast area is wet,the compound events of drying and heat will occur in summer.3) The effect of spring soil moisture on summer climate variability is mainly realized by adjusting the distribution of local evapotranspiration and net radiation energy.The study of the compound extreme events of high temperature,low humidity,and rainfall is of great significance in effectively preventing all kinds of disasters and safety accidents caused by them,protecting people's lives and property,and maintaining social production order.
Abstract:
Wind shear in the atmosphere is a serious threat to the safety of aircraft,especially the low-level wind shear which is an important factor affecting the aircraft taking off and landing.By using the Doppler radar velocity data to calculate the one-dimension tangential,one-dimensional radial and two-dimension composite shear,accurately judging the dangerous area of wind shear could provide timely warning for flight,taking off and landing.In this study,as the wind shear automatic identification product on the principal user processor(PUP) for Doppler radar applications has the shortcomings such as weak edge recognition and larger location errors,according to Doppler radar velocity distributions and taking advantage of least square fitting method,"fitting window" suitable for airborne radar parameters are chosen,and the several cases have been identified and analyzed.For the performance in wind shear's identification,location and edge discerning,the least square method could provide better reference of wind shear and warnings than PUP's identification products.
Wind shear in the atmosphere is a serious threat to the safety of aircraft,especially the low-level wind shear which is an important factor affecting the aircraft taking off and landing.By using the Doppler radar velocity data to calculate the one-dimension tangential,one-dimensional radial and two-dimension composite shear,accurately judging the dangerous area of wind shear could provide timely warning for flight,taking off and landing.In this study,as the wind shear automatic identification product on the principal user processor(PUP) for Doppler radar applications has the shortcomings such as weak edge recognition and larger location errors,according to Doppler radar velocity distributions and taking advantage of least square fitting method,"fitting window" suitable for airborne radar parameters are chosen,and the several cases have been identified and analyzed.For the performance in wind shear's identification,location and edge discerning,the least square method could provide better reference of wind shear and warnings than PUP's identification products.
Abstract:
Based on the hourly precipitation observed by automatic weather stations(AWS) in China and retrieved from CMORPH(CPC MORPHing technique) satellite data,the merged precipitation product at hourly/0.1°lat/0.1°lon temporal-spatial resolution in China is developed through the two-step merging algorithm of PDF(probability density function) and OI(optimal interpolation).In this paper,the quality of merged precipitation product is assessed from the points of temporal-spatial characteristics of error,accuracy at different precipitation rates and cumulative times,merging effect at three station network densities and monitoring capability of the heavy rainfall.Results indicate that:1)The merged precipitation product effectively uses the advantages of AWS observations and satellite product of CMORPH,so it is more reasonable both at the precipitation amount and spatial distribution;2)The regional mean bias and root-mean-square error of the merged precipitation product are decreased remarkably,and they have a little change with time;3)The relative bias of merged precipitation product is -1.675%,less than 15% and about 30% for the medium(1.0—2.5 mm/h),medium to large(1.0—8.0 mm/h) and heavy rainfall(≥8.0 mm/h),respectively,and the product quality is improved further with the cumulative time increases.The merged precipitation product can capture the precipitation process very well and have a definite advantage in the quantitatively rainfall monitoring.
Based on the hourly precipitation observed by automatic weather stations(AWS) in China and retrieved from CMORPH(CPC MORPHing technique) satellite data,the merged precipitation product at hourly/0.1°lat/0.1°lon temporal-spatial resolution in China is developed through the two-step merging algorithm of PDF(probability density function) and OI(optimal interpolation).In this paper,the quality of merged precipitation product is assessed from the points of temporal-spatial characteristics of error,accuracy at different precipitation rates and cumulative times,merging effect at three station network densities and monitoring capability of the heavy rainfall.Results indicate that:1)The merged precipitation product effectively uses the advantages of AWS observations and satellite product of CMORPH,so it is more reasonable both at the precipitation amount and spatial distribution;2)The regional mean bias and root-mean-square error of the merged precipitation product are decreased remarkably,and they have a little change with time;3)The relative bias of merged precipitation product is -1.675%,less than 15% and about 30% for the medium(1.0—2.5 mm/h),medium to large(1.0—8.0 mm/h) and heavy rainfall(≥8.0 mm/h),respectively,and the product quality is improved further with the cumulative time increases.The merged precipitation product can capture the precipitation process very well and have a definite advantage in the quantitatively rainfall monitoring.
2021,44(1): 39-49, DOI: 10.13878/j.cnki.dqkxxb.20201113007
Abstract:
The Arctic climate,an important component of the global climate system,has moved into a new state over the past 20 years.Scientific questions and possible consequences related to these changes are now front in the midst of many important issues that the world needs to deal with in the future.These changes,including prominent atmospheric and oceanic warming and sea ice melting have been largely attributed to a combined effect of anthropogenic forcing and internal variability of the climate system.This review highlights some findings from a number of studies conducted by my research group in the past few years.The studies collectively suggest that the high latitude atmospheric circulation that is sensitive to tropical SST forcing related to the interdecadal Pacific oscillation (IPO) plays a vital role in driving the interannual and interdecadal variability of Arctic sea ice by affecting the atmospheric temperature,moisture,clouds and radiative fluxes over sea ice.In particular,the teleconnection excited by a SST cooling over the tropical Pacific is suggested to cause an enhanced melting from 2007 to 2012.In addition,it suggests that a similar internal process may also play a role to cause strong sea ice melting in summer 2020.Furthermore,the model evaluation focusing on CMIP5 models finds that most climate models have a limitation to replicate this IPO-related teleconnection,raising awareness on an urgent need to investigate the cause of this bias in models.Thus,this review is meant to offer priorities for future Arctic research so that more efforts are targeted on critical scientific questions raised in this study.
The Arctic climate,an important component of the global climate system,has moved into a new state over the past 20 years.Scientific questions and possible consequences related to these changes are now front in the midst of many important issues that the world needs to deal with in the future.These changes,including prominent atmospheric and oceanic warming and sea ice melting have been largely attributed to a combined effect of anthropogenic forcing and internal variability of the climate system.This review highlights some findings from a number of studies conducted by my research group in the past few years.The studies collectively suggest that the high latitude atmospheric circulation that is sensitive to tropical SST forcing related to the interdecadal Pacific oscillation (IPO) plays a vital role in driving the interannual and interdecadal variability of Arctic sea ice by affecting the atmospheric temperature,moisture,clouds and radiative fluxes over sea ice.In particular,the teleconnection excited by a SST cooling over the tropical Pacific is suggested to cause an enhanced melting from 2007 to 2012.In addition,it suggests that a similar internal process may also play a role to cause strong sea ice melting in summer 2020.Furthermore,the model evaluation focusing on CMIP5 models finds that most climate models have a limitation to replicate this IPO-related teleconnection,raising awareness on an urgent need to investigate the cause of this bias in models.Thus,this review is meant to offer priorities for future Arctic research so that more efforts are targeted on critical scientific questions raised in this study.
2015,38(1): 27-36, DOI: 10.13878/j.cnki.dqkxxb.20130626001
Abstract:
The high-resolution numerical simulations of Hurricane Bonnie(1998) are used to analyze its intensity and structure changes in relation to its associated inertial stability under the influence of intense vertical wind shear during three different stages of its life cycle.Results show that Bonnie has high asymmetry and experiences an eyewall displacement cycle during its rapid intensifying stage.During its rapid structure change stage,the development of high inertial stability is consistent with the change in hurricane inner core size.The inertially stable region,which is usually present inside the eyewall,provides resistance to radial motions,and plays an important role in reducing the influence of vertical wind shear.The inertially stable region reduces the Rossby radius of deformation,and concentrates the latent heating,which is beneficial to the enhancing of the hurricane.This is an important factor in the development of inner core region of the hurricane.
The high-resolution numerical simulations of Hurricane Bonnie(1998) are used to analyze its intensity and structure changes in relation to its associated inertial stability under the influence of intense vertical wind shear during three different stages of its life cycle.Results show that Bonnie has high asymmetry and experiences an eyewall displacement cycle during its rapid intensifying stage.During its rapid structure change stage,the development of high inertial stability is consistent with the change in hurricane inner core size.The inertially stable region,which is usually present inside the eyewall,provides resistance to radial motions,and plays an important role in reducing the influence of vertical wind shear.The inertially stable region reduces the Rossby radius of deformation,and concentrates the latent heating,which is beneficial to the enhancing of the hurricane.This is an important factor in the development of inner core region of the hurricane.
2016,39(6): 722-734, DOI: 10.13878/j.cnki.dqkxxb.20161028003
Abstract:
The present paper has mainly analysed the process and mechanisms of genesis and development of the 2014-2016 mega El Niño event.It is shown that the entire lifecycle of the event is about 2 years(from April 2014 to May 2016),with four stages identified for its evolutive process:(1)Early and continuous westerly wind bursts(December 2013 to April 2014).The continuous three westerly wind burstsnot only changed the state of the easterly trade wind prevailing tropical central and easterly in the Pacific for long period of time,but also changed the cold water state in this region for the most recent 12 years,thus leading to SST rise and warming.Until early spring 2014,the SSTA exceeded 0.5℃,marking the possible occurrence of a new El Niño event.(2)Alternative weakening period(June 2014 to August 2015).Six westerly wind bursts continued to occur,thus maintaining and enhancing the warming of the equatorial central and eastern Pacific,while at the same time overcoming two periods of SST warming decrease or barrier,so that the initial development of El Niño was not aborted,and even changed into the stage of strong El Niño.Correspondingly,in the sub layer of the equatorial central and eastern Pacific,six warm Kelvin waves were observed to propagate eastward.The heat contents of these oceanic waves not only maintained the continuous warming in the equatorial central and eastern Pacific,but also caused El Niño to change from CP to EP type.(3)Peak period of development (September 2015 to February 2016).Two stronger westerly wind bursts were observed,which corresponded to very vigorous convective activity on the equatorial central and eastern Pacific.Rapid warming occurred in the Niño3.4 region,with 3℃observed in November 2015,classified as the mega-El Niño event.(4)Accelerating weakening stage(March to May 2016).The intensity of the El Niño rapidly weakened from 2 to 0.5℃ in the Niño3.4 region,then accelerated the transition to the cold water phase.In July to August 2016,the SSTA in the Niño3.4 region already approached -0.5℃.This rapid phase shift is a manifestation of the theory of delayed oscillation.From the above results,it is concluded that the development and shift of warm and cold phases is observationally consistent with the mechanism derived from the paradigm of the current theory of recharge oscillation and/or delayed oscillation theory.This clearly demonstrates that the results of the El Niño theory effectively underpin the development of related operational prediction.
The present paper has mainly analysed the process and mechanisms of genesis and development of the 2014-2016 mega El Niño event.It is shown that the entire lifecycle of the event is about 2 years(from April 2014 to May 2016),with four stages identified for its evolutive process:(1)Early and continuous westerly wind bursts(December 2013 to April 2014).The continuous three westerly wind burstsnot only changed the state of the easterly trade wind prevailing tropical central and easterly in the Pacific for long period of time,but also changed the cold water state in this region for the most recent 12 years,thus leading to SST rise and warming.Until early spring 2014,the SSTA exceeded 0.5℃,marking the possible occurrence of a new El Niño event.(2)Alternative weakening period(June 2014 to August 2015).Six westerly wind bursts continued to occur,thus maintaining and enhancing the warming of the equatorial central and eastern Pacific,while at the same time overcoming two periods of SST warming decrease or barrier,so that the initial development of El Niño was not aborted,and even changed into the stage of strong El Niño.Correspondingly,in the sub layer of the equatorial central and eastern Pacific,six warm Kelvin waves were observed to propagate eastward.The heat contents of these oceanic waves not only maintained the continuous warming in the equatorial central and eastern Pacific,but also caused El Niño to change from CP to EP type.(3)Peak period of development (September 2015 to February 2016).Two stronger westerly wind bursts were observed,which corresponded to very vigorous convective activity on the equatorial central and eastern Pacific.Rapid warming occurred in the Niño3.4 region,with 3℃observed in November 2015,classified as the mega-El Niño event.(4)Accelerating weakening stage(March to May 2016).The intensity of the El Niño rapidly weakened from 2 to 0.5℃ in the Niño3.4 region,then accelerated the transition to the cold water phase.In July to August 2016,the SSTA in the Niño3.4 region already approached -0.5℃.This rapid phase shift is a manifestation of the theory of delayed oscillation.From the above results,it is concluded that the development and shift of warm and cold phases is observationally consistent with the mechanism derived from the paradigm of the current theory of recharge oscillation and/or delayed oscillation theory.This clearly demonstrates that the results of the El Niño theory effectively underpin the development of related operational prediction.
JIANG Tong, ZHAI Jianqing, LUO Yong, SU Buda, CHAO Qingchen, WANG Yanjun, WANG Guojie, HUANG Jinlong, XU Runhong, GAO Miaoni, MIAO Lijuan
2022,45(4): 502-511, DOI: 10.13878/j.cnki.dqkxxb.20220529013
Abstract:
The second working group of the IPCC Sixth Assessment Report (IPCC AR6 WGⅡ) focuses on the impact,risk,adaptation and vulnerability of climate change.The report quantitatively assesses the impact of climate change on natural and human systems with the latest data,detailed evidence and diverse methods.Compared to AR5,the following progress has been made:Firstly,The content clarifies that the impact of climate change is attributable to three categories:anthropogenic climate forcing,non-climate factor action and weather sensitivity identification,127 key risks from climate change will become widespread or irreversible,and limiting global warming to 1.5 ℃ can greatly reduce climate change loss and damage to natural and human systems,pointing to the importance of adapting to transition.Secondly,AR6 WGⅡ adopts the latest combination of SSPs and RCPS in terms of evaluation method,which is more comprehensive.Thirdly,AR6 WGⅡ has focus on risks and solutions,and on the basis of AR5 WGⅡ,it is clarified that under different future warming scenarios,the risk level of the key risks facing the five “reasons for concern (RFCs)” will be relied on lower to very high levels of global warming.Finally,AR6 WGⅡ clarifies the urgency of climate action,combining adaptation and mitigation to support sustainable development is essential for climate resilience development pathways,pointing to the importance of immediate action to address climate risks.
The second working group of the IPCC Sixth Assessment Report (IPCC AR6 WGⅡ) focuses on the impact,risk,adaptation and vulnerability of climate change.The report quantitatively assesses the impact of climate change on natural and human systems with the latest data,detailed evidence and diverse methods.Compared to AR5,the following progress has been made:Firstly,The content clarifies that the impact of climate change is attributable to three categories:anthropogenic climate forcing,non-climate factor action and weather sensitivity identification,127 key risks from climate change will become widespread or irreversible,and limiting global warming to 1.5 ℃ can greatly reduce climate change loss and damage to natural and human systems,pointing to the importance of adapting to transition.Secondly,AR6 WGⅡ adopts the latest combination of SSPs and RCPS in terms of evaluation method,which is more comprehensive.Thirdly,AR6 WGⅡ has focus on risks and solutions,and on the basis of AR5 WGⅡ,it is clarified that under different future warming scenarios,the risk level of the key risks facing the five “reasons for concern (RFCs)” will be relied on lower to very high levels of global warming.Finally,AR6 WGⅡ clarifies the urgency of climate action,combining adaptation and mitigation to support sustainable development is essential for climate resilience development pathways,pointing to the importance of immediate action to address climate risks.
2014,37(5): 653-664, DOI: 10.13878/j.cnki.dqkxxb.20111230001
Abstract:
Studies have shown that large-scale monsoon gyre activity is closely associated with tropical cyclogenesis over the western North Pacific.In this study,two cases of monsoon gyre activities in 2002 and 2009 were first examined.It was found that a monsoon gyre can be linked to the formation of one or more tropical cyclones,which usually occur near or to the east of the gyre center.Further analysis of the monsoon gyre activity during the period of 2000—2009 indicates that tropical cyclogenesis mainly occurs near or to the east of the gyre center,although the definition of a monsoon gyre depends on its duration and the circulation intensity.It is suggested that the tropical cyclogensis may be associated with the Rossby wave energy dispersion of monsoon gyres.
Studies have shown that large-scale monsoon gyre activity is closely associated with tropical cyclogenesis over the western North Pacific.In this study,two cases of monsoon gyre activities in 2002 and 2009 were first examined.It was found that a monsoon gyre can be linked to the formation of one or more tropical cyclones,which usually occur near or to the east of the gyre center.Further analysis of the monsoon gyre activity during the period of 2000—2009 indicates that tropical cyclogenesis mainly occurs near or to the east of the gyre center,although the definition of a monsoon gyre depends on its duration and the circulation intensity.It is suggested that the tropical cyclogensis may be associated with the Rossby wave energy dispersion of monsoon gyres.
Abstract:
利用IAEA\WMO\GNIP的降水稳定同位素资料，分析了中国降水稳定同位素的时空分布特征及其影响因素。结果表明，整体来看我国降水稳定同位素有明显的大陆效应和高度效应。各地大气降水线存在地域差异，内陆地区同一站点冬、夏半年也有明显差异，显示出水汽团特性的不同。不同地区降水稳定同位素（δ和过量氘）的季节变化特征明显不同，表明主要水汽来源存在季节性差异。通过对比长序列降水稳定同位素的年际变化与季风和ENSO指数的关系，发现ENSO与降水稳定同位素有显著的正相关，但不一定通过影响降水量来引起降水稳定同位素（stable isotope in precipitation, SIP）的变化。重点分析了我国降水量效应、温度效应的特点，指出沿海和西南等季风区主要受降水量的影响，北方非季风区温度效应起主要作用，交叉地带则两种效应都有影响。
利用IAEA\WMO\GNIP的降水稳定同位素资料，分析了中国降水稳定同位素的时空分布特征及其影响因素。结果表明，整体来看我国降水稳定同位素有明显的大陆效应和高度效应。各地大气降水线存在地域差异，内陆地区同一站点冬、夏半年也有明显差异，显示出水汽团特性的不同。不同地区降水稳定同位素（δ和过量氘）的季节变化特征明显不同，表明主要水汽来源存在季节性差异。通过对比长序列降水稳定同位素的年际变化与季风和ENSO指数的关系，发现ENSO与降水稳定同位素有显著的正相关，但不一定通过影响降水量来引起降水稳定同位素（stable isotope in precipitation, SIP）的变化。重点分析了我国降水量效应、温度效应的特点，指出沿海和西南等季风区主要受降水量的影响，北方非季风区温度效应起主要作用，交叉地带则两种效应都有影响。
Abstract:
A new atmospheric correction algorithm based on dark object method and the look up table developed from MODTRAN model was introduced for Landsat images in the paper.The infomation of the satellite remote sensing images was used to support the atmospheric correction.The algorithm was applied to the Landsat ETM+imagery and comparisons show that the influence on Landsat imagery caused by molecules,water vapor,ozone,and aerosol particles in the atmosphere was effectively reduced after the correction.The surface reflectivity was more precisely,which is beneficial for remote sensing information extraction and thematic interpretation.
A new atmospheric correction algorithm based on dark object method and the look up table developed from MODTRAN model was introduced for Landsat images in the paper.The infomation of the satellite remote sensing images was used to support the atmospheric correction.The algorithm was applied to the Landsat ETM+imagery and comparisons show that the influence on Landsat imagery caused by molecules,water vapor,ozone,and aerosol particles in the atmosphere was effectively reduced after the correction.The surface reflectivity was more precisely,which is beneficial for remote sensing information extraction and thematic interpretation.
2015,38(2): 184-194, DOI: 10.13878/j.cnki.dqkxxb.20140508002
Abstract:
The observed SST data and CMIP5 data are used to analyze climate state and interdecadal variation of sea surface temperature(SST) over Northwest Pacific(20—60°N,120°E—120°W).Results indicate that the selected 22 models can simulate the climate state perfectly.More importantly,the selected models can simulate the annual and interdecadal variations of SST over Northwest Pacific.Total standard deviation of SST simulted by the models is the largest in Kuroshio extension region.The majority of models have an ability to simulate the first EOF mode of SST.The SST over Northwest Pacific has a significant interdecadal oscillation phenomenon.SSTs simulated by the 13/22 models have obvious interdecadal oscillations.Meanwhile,the simulated deviation of SST climate state has a great effect on the periodic oscillation of SST,especially in Kuroshio extension region.
The observed SST data and CMIP5 data are used to analyze climate state and interdecadal variation of sea surface temperature(SST) over Northwest Pacific(20—60°N,120°E—120°W).Results indicate that the selected 22 models can simulate the climate state perfectly.More importantly,the selected models can simulate the annual and interdecadal variations of SST over Northwest Pacific.Total standard deviation of SST simulted by the models is the largest in Kuroshio extension region.The majority of models have an ability to simulate the first EOF mode of SST.The SST over Northwest Pacific has a significant interdecadal oscillation phenomenon.SSTs simulated by the 13/22 models have obvious interdecadal oscillations.Meanwhile,the simulated deviation of SST climate state has a great effect on the periodic oscillation of SST,especially in Kuroshio extension region.
Abstract:
超级单体风暴常伴随着冰雹、雷雨大风等强对流天气，最本质的特征是有一持久深厚的几千米尺度的涡旋———中气旋。利用2003-2009年福建龙岩新一代天气雷达观测到的32次超级单体风暴，分析了超级单体风暴中气旋的时空分布、结构特征以及旋转速度大小、中气旋顶和底的高度、伸长厚度以及切变值等特征量。结果表明：90%以上的超级单体中尺度气旋是与冰雹、雷雨大风、短时强降水等强对流天气相联系的。统计8次有详细灾情的雷雨大风或冰雹天气过程发现，中气旋强度不断加强，中气旋厚度加大，最强切变中心突降时将产生大风或冰雹等强对流天气
超级单体风暴常伴随着冰雹、雷雨大风等强对流天气，最本质的特征是有一持久深厚的几千米尺度的涡旋———中气旋。利用2003-2009年福建龙岩新一代天气雷达观测到的32次超级单体风暴，分析了超级单体风暴中气旋的时空分布、结构特征以及旋转速度大小、中气旋顶和底的高度、伸长厚度以及切变值等特征量。结果表明：90%以上的超级单体中尺度气旋是与冰雹、雷雨大风、短时强降水等强对流天气相联系的。统计8次有详细灾情的雷雨大风或冰雹天气过程发现，中气旋强度不断加强，中气旋厚度加大，最强切变中心突降时将产生大风或冰雹等强对流天气
Abstract:
利用ＴＲＭＭ卫星上携带的闪电探测仪（ＬＩＳ）所获取的１０ａ闪电资料（１９９８—２００７年）对西南地区闪电活动的时空分布特征进行了分析。结果表明：该地区闪电次数的年差异较大，最多年份是最少年份的２倍多，闪电活动季节性特征非常明显，闪电主要集中在春末仲夏发生，呈现单峰值特征，４—８月是闪电高发期（约占全年总闪电活动的８４８３％）。闪电活动的日变化表明，闪电峰值区集中在傍晚、午夜前后两个时段，闪电谷值区出现在０９：００—１２：００，夜雷暴多，这是与其他地区闪电日变化显著不同的地方。在对闪电次数进行了探测效率订正后，根据ＬＩＳ注视时间，计算了闪电密度。西南地区闪电密度分布大体呈现：东部高，西部低；南部高，北部低。闪电密度较高、面积较大的高值中心位于中越交界的老山一带，非常明显的大片低发区主要位于西南西部地区。研究表明：西南地区闪电时空分布与当地的地形地势、水汽和地理环境条件等诸多因素有关。
利用ＴＲＭＭ卫星上携带的闪电探测仪（ＬＩＳ）所获取的１０ａ闪电资料（１９９８—２００７年）对西南地区闪电活动的时空分布特征进行了分析。结果表明：该地区闪电次数的年差异较大，最多年份是最少年份的２倍多，闪电活动季节性特征非常明显，闪电主要集中在春末仲夏发生，呈现单峰值特征，４—８月是闪电高发期（约占全年总闪电活动的８４８３％）。闪电活动的日变化表明，闪电峰值区集中在傍晚、午夜前后两个时段，闪电谷值区出现在０９：００—１２：００，夜雷暴多，这是与其他地区闪电日变化显著不同的地方。在对闪电次数进行了探测效率订正后，根据ＬＩＳ注视时间，计算了闪电密度。西南地区闪电密度分布大体呈现：东部高，西部低；南部高，北部低。闪电密度较高、面积较大的高值中心位于中越交界的老山一带，非常明显的大片低发区主要位于西南西部地区。研究表明：西南地区闪电时空分布与当地的地形地势、水汽和地理环境条件等诸多因素有关。
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- 1The impact of the Himalayan-Tibet Plateau on the monsoon region
- 2Major Achievements in Meteorology in Ancient China
- 3Discussion on calculation method of flowering date meeting of hybrid rice parents
- 4APPLICATION OF WAVELET TRANSFORMATION TO ANALYSIS OF MULTIPLE TIME SCALE CLIMATE CHANGE
- 5Quality assessment of hourly merged precipitation product over China
- 6Analysis and comparison of four kinds of circulation indices of Aleutian Low
- 7Multiscale structure features of a typical Meiyu frontal rainstorm process
- 8Evaluation of the four PBL schemes in WRF Model over complex topographic areas
- 9Analyses on Satellite Cloud Images and Doppler Radar Echo Features of a MCC Rainstorm Caused by Southwest Vortex
- 10CMIP5 projected changes in mean and extreme climate in the Belt and Road region
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