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  • 1  Quality assessment of hourly merged precipitation product over China
    SHEN Yan PAN Yang YU Jing-jing ZHAO Ping ZHOU Zi-jiang
    2013, 36(1):37-46.
    [Abstract](4916) [HTML](0) [PDF 4.97 M](18848) [Cited by](15)
    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.
    2  Characteristic analysis of two severe squall line processes in Jiangsu area
    YU Geng-kang WU Hai-ying ZENG Ming-jian YIN Dong-ping ZHANG Peng-bo
    2013, 36(1):47-59.
    [Abstract](2025) [HTML](0) [PDF 3.58 M](2941) [Cited by](12)
    Abstract:
    Based on the conventional observations,NECP/NCAR reanalysis data,automatic weather station intensive observations and Doppler radar data,this paper contrasts the two typical squall line processes in Jiangsu and its surrounding areas on 28 Apirl 2006 and 14 June 2009.Results show that,prior to the two squall line processes,the warm advection obviously occurs in the lower troposphere and the cold advection appears in the middle-upper troposphere,which is helpful for the formation and development of stratification instability.During the movement and development of squall lines,a clear convergence line occurs in the surface wind field,which plays an important role in the triggering and maintenance of the squall lines.There are obvious differences of thermal and dynamic structures between the environment fields of the two processes.For the thermal structures,the former happens in spring when cold air is still strong and warm advection in the lower troposphere is one of main reasons of stratification instability,and the latter happens in summer when warm moist air is active and cold air invasion in middle-upper troposphere deserves attention greatly.The dynamic analysis shows that low level convergence and lifting conditions of the former are better than those of the latter.However,the thermal conditions of the latter are predominant,and it is easier to develop once the convection starts.
    3  Multimodel ensemble forecasts of surface air temperature and precipitation using TIGGE datasets
    ZHI Xie-fei JI Xiao-dong ZHANG Jing ZHANG Ling BAI Yong-qing LIN Chun-ze
    2013, 36(3):257-266.
    [Abstract](2102) [HTML](0) [PDF 3.70 M](2920) [Cited by](9)
    Abstract:
    Based on the ensemble forecasting data of China Meteorological Administration(CMA),European Centre for Medium Range Weather Forecasts(ECMWF),Japan Meteorological Agency(JMA),U.S.National Centers for Environmental Prediction(NCEP),and United Kingdom Met Office(UKMO) in the TIGGE datasets,the multimodel ensemble forecasting techniques have been investigated.Results show that the multimodel ensemble forecasts are superior to that of the individual model.However,the improvement of multimodel ensemble forecast skill is different for different meteorological elements.The multimodel superensemble with running training period(R-SUP) has the best performance for surface air temperature in the Northern Hemisphere.For precipitation forecast in the Northern Hemisphere,the bias-removed ensemble mean(BREM) is more skillful and stable than every single model.In addition,the multimodel ensemble forecasting experiments of extreme weather event with freezing rain and snow over southern China during early 2008 have been conducted by using BREM with running training period(R-BREM).Taking root-mean-square errors(RMSEs) of ECMWF 96 h forecasts as the criterion,the forecast lead time of surface air temperature over the southeastern coast of China may be prolonged from 96 h to 192 h by using the R-BREM technique.And the threat scores(TS) of the light and moderate rain forecasts have been significantly improved except for some particular lead time.
    4  Characteristic comparison between the rapid intensification of tropical cyclones in easterly and westerly wind shear over the Northwest Pacific
    WANG Wei YU Jin-hua
    2013, 36(3):337-345.
    [Abstract](3438) [HTML](0) [PDF 3.55 M](4997) [Cited by](8)
    Abstract:
    Based on the tropical cyclone best track data from the Joint Typhoon Warning Center (JTWC) and the NCEP/NCAR reanalysis data from 1980 to 2009,we set a threshold for rapid intensification tropical cyclones (RITC) as 35 kn,which was the magnitude of intensity change of tropical cyclones in a period of 24 h with the accumulative probability of 96% over the western North Pacific.According to zonal wind shear between 200 hPa and 850 hPa,the paper divided the vertical wind shear (WS) into the westerly vertical wind shear (WWS) and easterly vertical wind shear (EWS) and compared the characteristics of rapid intensification of tropical cyclones in EWSwith those inWWS.The results show that about 70% of RITCs occur inEWS.There are most RITCs in September,whose initial intensity are between 65 and 70 kn.In largeEWS,abundant vapor comes from southwest at 850 hPa.At 500 hPa and 200 hPa,the Pacific subtropical anticyclone is strong and the ridge line is situated in north area.The temperature in outflow layer is below -79 ℃.In large WWS,the water vapor is from southeast at 850 hPa.At 500 hPa,subtropical high is split into several centers.Compared with that of the former,the divergence field of RITCs at 200 hPa is weaker.And the temperature in outflow layer is about -76 ℃.
    5  Characterization of visibility variation trend and its influence factors in Nanjing
    HOU Ling AN Jun-lin ZHU Bin
    2014, 37(1):91-98.
    [Abstract](1652) [HTML](0) [PDF 1.05 M](3570) [Cited by](7)
    Abstract:
    Visibility variation trends from 1980 to 2005 have been constructed using four different statistical methods:Ridit analysis,cumulative percentiles,frequency of "very good" visibility,and annual and seasonal means.Improvements in visibility were experienced from 1980 to 1984.A decline trend can be observed after 1985 with some fluctuations in the process.In these 26 years,the mean daily visibility was 8.59 km with the maximum at 29.25 km and the minimum at 0.55 km,respectively.There were obvious seasonal and daily variation features in visibility.It was worst in winter and best in summer in one year while it was worst at 08:00 BST and best at 14:00 BST in one day.Visibility showed a positive correlation with wind speed and a negative correlation with relative humidity.However,temperature and atmospheric pressure showed comparatively little correlation with it.PM10 was the major pollutant in Nanjing.Curve estimation of daily mean PM10 mass concentration and the visibility presented a negative correlation and the coefficient was the largest in autumn and the smallest in summer.A regression model based on relative humidity,PM10,wind speed and temperature has been developed.There were seasonal differences in the coactions of air pollution and meteorological condition on visibility,which was worse in summer than that in the other three seasons.
    6  Extraction of paddy planting areas based on MODIS vegetation index time series and linear spectral mixture model
    LI Gen JING Yuan-shu WANG Lin YANG Shen-bin
    2014, 37(1):119-126.
    [Abstract](1291) [HTML](0) [PDF 2.76 M](3137) [Cited by](7)
    Abstract:
    Paddy rice is one of the main crops in China.Timely information acquisition of rice planting area and spatial distribution at a large scale is of great significance in guiding rice production and regulating regional balance of supply and demand.In order to obtain paddy field area of Jiangsu Province,three types of vegetation indexes(including NDVI(normalized difference vegetation index),EVI(enhanced vegetation index),and LSWI(land surface water index)) are calculated by using the MODIS09A1 data from 2009 to 2011.Based on the temporal variation characteristics of EVI in different growth stages of rice,the key growth period of rice area extraction extracts is determined.According to the characteristics of rice transplanting period with high soil moisture,NDVI,EVI and LSWI are used to identify potential planting area of rice.The linear spectral mixture model is applied to decompose the mixed pixel of potential rice area,and the rice spatial distribution is obtained in Jiangsu Province from 2009 to 2011.Finally,selecting the typical sample area of rice,the rice planting area and spatial distribution are extracted by using HJ-1 CCD(30 m) data,and the results are used as reference data to verify the extraction accuracy.Meanwhile,the statistical rice planting area of Jiangsu Province from the statistical department is also used to verify the rice area.The error is within 10% by two methods of the statistical data and HJ-1 CCD(30 m) data.The research shows that it can more accurately extract a large range of rice planting area by using MODIS09A1 data and the linear spectral mixture model.
    7  Characteristics of PM10 and PM2.5 during summer time of 2007 and 2008 at Beijing National Stadium
    LI Xue LIU Zi-rui REN Xi-yan LI Xin WANG Yue-si
    2012, 35(2):197-204.
    [Abstract](1197) [HTML](0) [PDF 0.00 Byte](129) [Cited by](6)
    Abstract:
    In order to investigate the variation characteristics of atmospheric particle pollution in the Olympic Village and evaluate the effect of pollution control measures on particle matter concentrations,the on-line measurements of particle mass concentration(PM10 and PM2.5) using TEOM were conducted on the rooftop of a six-floor building in the Institute of Remote Sensing Applications,Chinese Academy of Sciences,during both summer of 2007 and 2008.Results show that the average mass concentration of PM10 and PM2.5 during summer of 2007 are 153.9 and 71.2 μg·m-3,while the average mass concentration of PM10 and PM2.5 during summer of 2008 are 85.2 and 52.8 μg·m-3,respectively.Compared with the same period of one year before,the average mass concentration of PM10 and PM2.5 decrease by 44.5% and 25.1%,respectively,during the Olympic Games.Two typical particle pollution processes are selected to compare the variation difference of particle mass concentrations before and during the Olympic Games.The result shows that the relative humidity increasing and air masses transportation from south regions both together easily lead to the increasing of atmospheric particles,whereas the rainfall events and air mass transportation from north regions have a great effect on the scavenging of particle matter.In the similar weather conditions,the daily growth rate of fine particles in pollution accumulation process are 25.1 and 13.9 μg·m-3·d-1,while the daily growth rate of coarse particles are 20.8 and 2.2 μg·m-3·d-1,respectively,before and during Olympic Games.The daily growth rate of coarse and fine particles in pollution process during Olympic Games are significantly and slightly lower than those in pollution process before Olympic Games,which indicates that the implementation of pollution control measures during the Olympic Games has a great effect on the decreasing of particle matter,especially on the reduction of coarse particles.
    8  Observation analysis on spatial and temporal distribution characteristics of summer urban heat island in Nanjing
    LIU Shou-dong JIANG Run WANG Cheng-gang WANG Yong-wei
    2014, 37(1):19-27.
    [Abstract](2235) [HTML](0) [PDF 4.08 M](2929) [Cited by](6)
    Abstract:
    Using the three dimensional observation test data of urban heat island(UHI) in Nanjing in summer 2010,spatial and temporal distribution characteristics of urban heat island under typical weather conditions were analyzed.The results showed that daily mean UHI intensity on sunny days was over 1 ℃ in Nanjing in summer.UHI intensity was stronger and more stable during nighttime than that in daytime,with UHI distribution displaying directional characteristic and corresponding well to urban land-use conditions.During daytime,mixed layer in urban areas developed faster and was higher than that in the suburbs.During nighttime,there existed a long lasting convective mixed layer at low altitude in the city due to the unstable atmospheric stratification and the roughness of the underlying surface,which was as thick as more than 250 m.Owing to the storage of a large amount of heat and strong turbulent transport in urban underlying surface,heat island came into being in urban boundary layer,with UHI intensity decreasing with height.Heat island in boundary layer extended up to 900 m in daytime and maintained at 300 m at nighttime.
    9  Evaluation of the four PBL schemes in WRF Model over complex topographic areas
    ZHANG Xiao-pei YIN Yan
    2013, 36(1):68-76.
    [Abstract](3625) [HTML](0) [PDF 6.28 M](6249) [Cited by](5)
    Abstract:
    In order to simulate meteorological parameters more accurately in the Planetary Boundary Layer(PBL) over complex terrain,the SRTM3 data from NASA was used in WRF model.With configuration of four PBL parameterization schemes(YSU scheme,ACM2 scheme,MYN scheme,and BL scheme) and two geographical data(SRTM3,GTOPO30),meteorological parameters in the PBL of the Mt Huang area during 24—25 April 2008 were evaluated.Temperature and dewpoint temperature of 2 m,wind speed of 10 m and water vapor distribution from simulation were contrasted to the observational data from 19 meteorological stations and 2 sounding stations in the Mt Huang area.Results show that YSU scheme was best for 2 m temperature simulation and ACM2 scheme was best for 2 m dewpoint temperature and 10 m wind speed simulation in the four PBL schemes with both geographical data;when SRTM3 data was used in WRF model,the mean RMSE of 2 m temperature simulated by the four PBL schemes were reduced by 3.79%(YSU scheme),2.48%(ACM2 scheme),3.8%(MYN scheme),and 0.87%(BL scheme), respectively;for 2 m dewpoint temperature,only the mean RMSE by MYN scheme was reduced by 0.59%,while the mean RMSE of YSU,BL and ACM2 schemes increased by 1.39%,0.49%,and 0.89%,respectively;as to 10 m wind speed,only the mean RMSE by ACM2 scheme was reduced by 2.28%,while the mean RMSE of YSU,MYN, and BL schemes increased by 0.22%,2.32%,and 2.45%,respectively;for the vertical distribution of water vapor from sounding report,all of the four PBL schemes can successfully simulate the vertical distribution tendency of water vapor,but all results turned out to be much moister;by using STRM3 data,the vertical distribution of water vapor simulated by ACM2 scheme was improved on low layer during some periods of time.
    10  Research on the influence of the mixed layer depth anomaly over the north Pacific on the precipitation in China in summer
    LI Li-ping CHEN Li-ping JIN Li-li XU Guan-yu
    2013, 36(1):20-28.
    [Abstract](2141) [HTML](0) [PDF 3.40 M](2864) [Cited by](5)
    Abstract:
    By using GODAS monthly mixed layer depth(MLD) and 160-station monthly precipitation data in China,the seasonal and interannual characteristics of MLD are analyzed over the north Pacific,along with the influences of MLD interannual anomaly on summer rainfall in China discussed.The results show that:1) The MLD is the deepest over the latitudes from 30 to 40°N and is larger in winter and spring than in summer and autumn.2) The interannual anomaly is most prominent over the middle part of the north Pacific near the international date line in four seasons;but only the MLD anomaly is somewhat related to ENSO in summer,and MLD is of interdecadal anomaly characteristics in autumn,winter and spring.3)When MLD increases over western and middle part of the north and central area of Pacific in the previous winter,the precipitation may decrease over the part of the lower Yellow River,Huang-huai,Jiang-huai and to the south of the Yangtze River reaches(except the south of Guangxi) and the precipitation may increase in He-tao,east part of Neimeng and most part of Northeast China in the following year.
    11  Impacts of climate change on food-crops production in Jiangsu Province from 1986 to 2010
    PAN Ao-da CAO Ying CHEN Hai-shan SUN Shan-lei
    2013, 36(2):217-228.
    [Abstract](1426) [HTML](0) [PDF 2.39 M](2223) [Cited by](5)
    Abstract:
    Based on the observations of 63 conventional meteorological stations and the investigated data of food-crops production in Jiangsu Province from 1986 to 2010,this paper studied the characteristics of climate change on three time scales in north,central and south Jiangsu,and the whole province.Based on the one-dimensional linear regression equation with the bootstrap resampling method,this paper studied the responses of the food-crops production to climate changes on the three time scales of crop-year(from November to October the next year),the growth seasons of summer(from Novemeber to May the next year) and autumn(from June to October) crops,and month.The influences of climate changes on the food-crops yield and the contributions of each climate factor in the past 25 years were quantitatively estimated.Results show that:1)In north,central and south Jiangsu,and the whole province,the climate factors are different on the time scales of crop-year,the growth season of summer and autumn crops and month,with some spatial-temporal differences.Under the combined impacts of the developing agricultural managements and technologies,and climate change,the food-crops yield per hectare in the four study areas increases significantly(p>0.01),with increasing trend of 66.89 kg·hm-2·a-1 in the whole province.2)Except that the response of the food-crops yield in south Jiangsu to climate change on the time scale of crop-year is not significant,the negative response of the food-crops yield to precipitation(the food-crops yield decreases when precipitation increases,and v.v.) can be found in the four study areas on the three time scales,indicating that precipitation variation plays an important role in the food-crops production.When precipitation increases(decreases),the food-crops yield in north and south Jiangsu,and Jiangsu decreases (increases),with the mean rates of 0.19%·(10 mm)-1,0.09%·(10 mm)-1 and 0.11%·(10 mm)-1,respectively.3)Results of the three models show that the food-crops production in north and south Jiangsu,and Jiangsu all decreases due to climate change.Results of Model-C established by monthly climate factors reveal that climate change leads to the food-crops yield per hectare(total production) decrease of -6.51%·(10 a)-1(-11.28×108 kg·(10 a)-1),-3.27%·(10 a)-1(-2.36×108 kg·(10 a)-1) and-1.34%·(10 a)-1(-4.45×108 kg·(10 a)-1) in north and south Jiangsu,and Jiangsu,respectively.Additionally,it is very necessary and critical to pay enough attention on the effects of monthly climate change in order to completely and systematically evaluate effects of climate change on food-crops production.
    12  Projection of heavy rainfall events in the middle and lower reaches of the Yangtze River valley in the 21st century under different representative concentration pathways
    HAN Le-qiong HAN Zhe LI Shuang-lin
    2014, 37(5):529-540. DOI: 10.13878/j.cnki.dqkxxb.20130512001
    [Abstract](1279) [HTML](0) [PDF 4.79 M](2376) [Cited by](5)
    Abstract:
    This paper evaluates the future projection of heavy rainfall events in the middle and lower reaches of the Yangtze River valley based on outputs of eight coupled models attending the Coupled Model Intercomparison Project phase 5(CMIP5) from IPCC AR5.The experiments under different representative concentration pathways(RCPs) are compared with each other,and with the previous CMIP3 experiments as well.The outputs from the historical simulation of CMIP5 are also utilized as a base to derive future trends.The results suggest an agreement among all the CMIP5 models,in that both the strength and the occurrence frequency of heavy rainfall events are projected to increase in the 21st century relative to the last twenty years of the 20th century(1980—1999).In contrast,the strength increase in the east of the region is even greater than that in the west.Besides,the interannual variability of heavy rainfall events is also projected to enhance in the future.As for different RCPs,the projected increases in the strength and occurrence frequency of heavy rainfall events in RCP2.6 and RCP8.5 are greater than those in RCP4.5.In comparison to CMIP3,the projected increases in the strength and occurrence frequency are even larger,albeit a significant difference in the spatial distribution in the latter projection.The projected maximum increase in the rainfall amplitude in CMIP3 is located in the central region,while it is in the east of the region in CMIP5.
    13  Heavy haze events during December 2013 in Nanjing
    ZHENG Longfei XIE Yuning LIU Qiang HUANG Xin NIE Wei DING Aijun
    2016, 39(4):546-553. DOI: 10.13878/j.cnki.dqkxxb.20160212001
    [Abstract](1076) [HTML](0) [PDF 4.77 M](2462) [Cited by](5)
    Abstract:
    Particular matter (PM) is one of the major pollutants in China.The radiation balance,visibility and human health can be strongly influenced by high concentrations of PM.Also,roduction rates of relevant heterogeneous reactions can be dramatically enhanced by significant levels of PM.Due to local anthropogenic emissions and the effect of regional transport,haze events occur frequently in the Yangtze River Delta (YRD),severely impacting upon the everyday and working lives of citizens.In this study,an intensive field campaign was conducted in December 2013 at a regional background site in Nanjing referred to as SORPES (Station for Observing Regional Processes of the Earth System) and,based on the data collected,the formation mechanism of haze pollution in wintertime was discussed and analyzed with a focus on the aerosol chemical composition and synoptic pattern.An online composition analysis instrument named MARGA (Monitoring Instrument for Aerosols and Gases) was used to measure water-soluble ions such as NO3-,SO42-,NH+4,Cl-,K+,Na+,Ca2+ and Mg2+ in the fine PM (PM2.5) fraction.Meanwhile,the gases SO2,NOx and O3 were measured by a trace gas instrument manufactured by Thermo Fisher Scientific (Massachusetts,USA).In order to study the synoptic pattern during hazy days,weather systems were analyzed using data from NECP.Moreover,the HYSPLIT model was used to simulate the atmospheric transport and dispersion of pollutant plumes originating from various air mass sources.HYSPLIT has capabilities ranging from simple trajectories to complex dispersion and deposition calculations for both puffs and particles.It can simulate dispersion based on input variables (wind,temperature,pressure etc.) from various meteorological models.These fields can then be integrated both in space and time to with respect to particles' positions in order to simulate the dispersive nature of the atmosphere.The results showed that the monthly average concentration of PM2.5 was 142 μg·m-3 and the water soluble ions (NO3-,SO42-,NH4+,Cl-,K+,Na+,Ca2+and Mg2+) contributed about 62% to the total mass concentration of PM2.5.Two heavy haze events were observed during the campagin.The concentration of PM2.5 reached 267 μg·m-3 in the first event and 150 μg·m-3in the second event,during which three major inorganic ions (sulfate,nitrate and ammonium)accounted for 63.6% and 66.4%,respectively.Both haze events lasted for several continuous days with very low visibility-only 1.9 km in the first event and 4.7 km in the second.Aerosols in the first event were mostly secondarily formed,with a stable weather system and lower mixing layer.The higher temperature and humidity compared to the second event provided appropriate conditions for the heterogeneous transformation of particles in the surface layer.HYSPLIT showed that the air masses of the first event mainly originated from local Nanjing and the surrounding YRD.However,the second event was largely influenced by long-range transport from the North China Plain.The formation of sulfate and nitrate in daytime was observed during both haze events,which mainly came from homogeneous reactions.Meanwhile,nighttime heterogeneous or aqueous-phase reactions contributed to the first event only.The catalytic oxidation of metal ions or liquid-phase oxidation of NO2 may have been important mechanisms through which sulfate formed at night in first haze event.
    14  Features of moisture transport in the Yangtze-Huaihe River Basin during the Meiyu season in the last 50 years
    WANG Zhiyi GAO Qingjiu HU Banghui SUN Yuting
    2017, 40(1):48-60. DOI: 10.13878/j.cnki.dqkxxb.20150916002
    [Abstract](1144) [HTML](0) [PDF 6.99 M](2490) [Cited by](5)
    Abstract:
    Meiyu refers to a special season of rainy weather that usually happens in early summer in China's Yangtze River region.The intensity,range and other characteristics of Meiyu precipitation,including trends of change,have important influences on the economic development,agricultural production,and lives of the people residing in this region.In recent years,an abnormal enhancement in rainstorm intensity,an increase in associated damage,and other atypical features have become more frequent.In other words,the Meiyu has begun to show new characteristics against the background of global warming.Choosing the moisture source during the Meiyu season as the starting point,the vapor transport characteristics over China's Yangtze River region were studied and discussed in this paper.The spatiotemporal characteristics of June-July Asian monsoon moisture transport and its relationship with precipitation over the Yangtze-Huaihe River Basin were investigated using ERA reanalysis data of wind and pressure,along with APHRODITE daily precipitation data for East Asia,over the period 1958-2007.Results showed that different moisture paths connected with different regional rainfall in the Yangtze-Huaihe River Basin.By calculating the water vapor flux intensity,three main water vapor paths that influence Meiyu precipitation in the Yangtze-Huaihe River Basin were partitioned out.The strongest transmission intensity belonged to the southwest path,but the greater contribution to Meiyu precipitation was from the South China Sea path and the southeast path.Meridional water vapor transport of the southwest path enhanced local precipitation in the western part of the Yangtze-Huaihe River Basin,while zonal transport reduced precipitation in the northern part;The influence of the South China Sea path on precipitation over the Yangtze-Huaihe River Basin featured reverse characteristics in the north and south.The precipitation in the area north of the basin was weakened by the direction of the meridional transport,while most areas south of the basin experienced an increase in precipitation.When water vapor transport was anomalously strong,there was less rain in the northern part of the basin and rain in the southeast;The zonal transport of the southeast path featured a significant increase in precipitation in the southwest and central to northern parts of the Yangtze-Huaihe River Basin.When the water vapor transport path was strong,a corresponding increase in precipitation in the central eastern Yangtze-Huaihe river basin was found.The characteristics of moisture transport during the Mei-yu season were found to exhibit interannual variation.Furthermore,precipitation intensity over the Yangtze-Huaihe River Basin was closely related to the strength of moisture transport.Using correlation analysis to identify the most significant areas of water vapor transport,nd combined with the synthesis of difference analysis of anomalous years of water vapor transport,he impact of water vapor transport intensity on the strength of Meiyu precipitation in the Yangtze-Huaihe River Basin was studied.The results of the correlation analysis and the synthesis of difference demonstrated that precipitation during the Mei-yu period over the Yangtze-Huaihe River Basin was mainly influenced by the southeast path of moisture transport,when the moisture transport derived from the West Pacific.The western Pacific Ocean contributed much more than the Indian Ocean in terms of vapor transfer into the Yangtze-Huaihe River Basin region.Against the background of global warming,the correlation and range of influence between the precipitation of the Meiyu season over the Yangtze-Huaihe River Basin and the intensity of the main water vapor transport sources has changed.The effect of western Pacific transportation into the Yangtze-Huaihe River Basin region on the enhancement of rainfall has weakened,while the scale of the decreased influence of Indian Ocean transportation on rainfall has significantly increased.Since the 1980s,the slowly increasing trend of precipitation over the Yangtze-Huaihe River Basin has been related to the moisture transportation anomalies caused by the easing of Asian circulation anomalies as a result of global warming.
    15  Extended-range probabilistic forecasts of surface air temperature over East Asia during boreal winter
    JI Luying ZHI Xiefei ZHU Shoupeng
    2017, 40(3):346-355. DOI: 10.13878/j.cnki.dqkxxb.20161106001
    [Abstract](1125) [HTML](0) [PDF 2.12 M](2539) [Cited by](5)
    Abstract:
    Based on the TIGGE datasets including the European Centre for Medium-Range Weather Forecasts(ECMWF), the U.S.National Centers for Environmental Prediction(NCEP), the United Kingdom Met Office(UKMO) and its multi-center ensemble systems, Bayesian Model Averaging(BMA) probabilistic forecasts of winter surface air temperature over East Asia are established.Anomaly correlation coefficient(ACC) and root mean square(RMSE) are used for the evaluation of the BMA deterministic forecasts.Furthermore, Brier score(BS), Ranked probability score(RPS), BSS and RPSS are applied to evaluate the performance of BMA probabilistic forecasts.The results show that the BMA forecast distributions are considerably better calibrated than the raw ensemble forecasts, and BMA forecasts of ECMWF, NCEP and UKMO EPSs provide better deterministic forecasts than the individual model forecasts.The BMA models for multi-center EPSs outperform those for single-center EPS for lead times of 240-360 h, and the optimal length of the training period is about 35 days.In addition, BMA provides a more reasonable probability distribution, which depicts the quantitative uncertainty of the forecasts.The uncertainty on the land(higher latitude) is larger than that on the sea(lower latitude).
    16  A study on potential sources and transportation pathways of PM10 in spring in Lanzhou
    LIU Na YU Ye CHEN Jin-bei HE Jian-jun ZHAO Su-ping
    2012, 35(4):477-486.
    [Abstract](1357) [HTML](0) [PDF 2.24 M](2032) [Cited by](4)
    Abstract:
    Three-dimensional 4-day backward trajectories arriving in Lanzhou at 500m high were calculated every 6 h by using HYSPLIT-4 trajectory model in spring of 2001 to 2008.The 8 years were divided into two categories:high dust year (2001,2002,2004 and 2006) and low dust year (2003,2005,2007 and 2008).Cluster analysis,potential source contribution function (PSCF) model,and concentration-weighted trajectory (CWT) method were used to evaluate the transportation pathways and potential source regions of Lanzhou PM10 pollution in spring.Results indicate that the western and northwestern pathways,respectively accounting for 33% and 19.4% of all trajectories,were major pathways leading to high springtime PM10 loadings in Lanzhou in 2001,2002,2004 and 2006.However,the major pathways were the western and the northern pathways in 2003,2005,2007 and 2008,accounting for 23.6% and 18%,respectively.There were six potential source regions that had effect on PM10concentration in Lanzhou,including Tarim Basin and Turpan Basin in Xinjiang,Qaidam Basin in Qinghai,Hexi Corridor in Gansu Province,the desert and gobi area in central and western Inner Mongolia.
    17  Characteristics of SO2, NO2, O3 volume fractions and their relationship with weather conditions at Linan in summer and winter
    FAN Yang FAN Shu-xian ZHANG Hong-liang ZU Fan MENG Qing-zi HE Jia-bao
    2013, 36(1):121-128.
    [Abstract](1834) [HTML](0) [PDF 3.87 M](2655) [Cited by](4)
    Abstract:
    This paper studies NO2,SO2,and O3 at Linan in summer and winter of 2003 and 2004.Results show that the mean volume fractions of NO2 and SO2 are 19.48×10-9 and 35.74×10-9 in winter,respectively,which are higher than those in summer(4.81×10-9 and 8.12×10-9, respectively).The mean volume fractions of O3 is 33.55×10-9 in summer,which is higher than that in winter (25.44×10-9).The volume fractions of NO2 and SO2 during the daytime are lower than those during the nighttime.The diurnal variation of NO2volume fraction shows the single valley and single peak distribution with its peak during the nighttime.The diurnal variation of O3 volume fraction is similar to NO2,but its peak appears during the daytime.The volume fractions of NO2 and SO2 show an obvious "Holiday Effect",and are obviously lower during weekends than those during weekdays,with the highest on Fridays.The volume fraction of O3 does not have an obvious "Holiday Effect".The wet removal efficiency of precipitation to SO2 is more obvious than to NO2.By contrast with the different wind directions,the higher volume fractions of NO2 and SO2 are affected by NW and WNW winds in summer,while by NE,SW and SSW winds in winter.The influence of wind direction on the ozone is complex,which is relevant to local photochemical reactions.
    18  Multi-model ensemble forecasts of surface air temperature in the extended range using the TIGGE dataset
    CUI Hui-hui ZHI Xie-fei
    2013, 36(2):165-173.
    [Abstract](1428) [HTML](0) [PDF 4.34 M](2675) [Cited by](4)
    Abstract:
    Based on the 10-15 days extended range ensemble forecasts of CMC,ECMWF,UKMO and NCEP in the TIGGE dataset,the multi-model ensemble forecasts of surface air temperature in the Northern Hemisphere middle latitudes during the period from 1 July to 30 September 2008 have been conducted by using EMN(Ensemble Mean),BREM(Bias-Removed Ensemble Mean) and SUP(Multi-model Superensemble),respectively.Meanwhile,the Talagrand distribution,ensemble spread,and RMS error are utilized to evaluate the forecast skills of each single forecast system.As is known that the precision of daily forecasts in extended range is relatively low,people pay more attention to the prediction precision of weather process in extended range.The daily data of each single forecast system and the daily observed data are processed by the moving average method.The processed data are also conducted with multi-model ensemble means.Finally,the training period of SUP is tested.Results show that four single forecast system’s ensemble spread are low compared with RMS error.ECMWF is the best single system,NCEP follows and UKMO is the worst.The forecast skills of EMN,BREM and SUP are all higher than single system and SUP is the best ensemble method.Moving average methods further improve the forecast skill of surface air temperature and the longer of moving step is,the better of the prediction results are.For the training period of SUP about daily and 3-day moving average,75 days are the best training period for 10-12 d forecasts and 35 days are the best for 13-15 d forecasts.For 5-day and 7-day moving average,the best training period is 35 days at all forecasting time.

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