Abstract:Based on the NCEP/NCAR reanalysis data,the pentad time series of the western Pacific subtropic high ridge index is calculated;the time series is analyzed by the phase space reconstruction technique,and during the course of phase space construction,the optimal delay time and embedding dimension of phase space is discussed and determined,and the counterfeit phase plot is also given;then the correlation dimension of subtropic high ridge index series is calculated,to be 3.10±0.05.According to the computation of dynamic parameters and the analysis of recurrence plot by the phase space reconstruction,the dynamic randomicity and complexity of subtropic high is discussed.The analysis result will be of importance to understand the complexity and predictability of subtropical high system,and it will also have special reference value to the subtropical dynamic model retrieval.

Abstract:Three circulation indices are defined for closed pressure systems,which are area index S,strength index P,center longitude/latitude position index(λ_c,φ_c).Their calculation methods are also put forward by using NCEP/NCAR monthly mean pressure(geopotential height) fields.The above circulation indices of 500 hPa north polar vortex are calculated and their climatological time series are constructed respectively.Results indicate that these three indices can simply and quantitatively describe northern polar vortex’s seasonal and interannual variability,and also suitable for describing other closed systems of pressure or the other meteorological element fields on the spherical surface.

Abstract:The diurnal evolution of clear air echo(CAE) and its association with turbulent mixing in the boundary layer are investigated using the CAE data observed by Nanjing Doppler radar on 23 June,2005 and the surface meteorological observations of the same time period.The temporal evolution of the reflectivity of CAE is analyzed against the evolution of refractive index,N,surface temperature,T,dew point,td,vapor pressure,e,surface pressure,p.The results show that at night turbulences occured when gradients of T,p,e were moderate,but they were not strong enough to completely mix airs of the surface layer.Along with the inerease in the fluctuation of refrative index ΔN,the CAE appeared.Temperature rising after sunrise gradually strengthened turbulances,which resulted in fully mixing of air and the reduction of T,p,e gradients and ΔN in the surface layer,then,the weakening and vanish of CAE.

Abstract:A rainstorm case in the Changjiang-Huaihe River valley on 5th July 2003 is studied in the paper,and the preprocessing and error estimation of radar radial velocity are discussed.Contrast experiments for assimilating grid radial velocity data and E-VAP(extended velocity azimuth processing) retrieved data into the nonhydrostatic meso-scale model WRF(weather research and forecasting) are performed,and results show that the direct assimilation of radial velocity improved the initial wind fields with more meso-scale information and rationalized the distribution of vertical velocity,and also improved the distribution of water vapor through the effect of winds.The assimilation of the retrieved wind data was able to increase the meso-scale information in the initial wind fields,but its effect was not as good as direct assimilation.Precipitation fields analysis shows that the direct and retrieved data assimilation both improved the rainfall forecasts,but as far as assimilation effect on precipitation concerned,the direct assimilation is better than the retrieval assimilation,and the assimilation experiments with 5—6 min assimilation interval are better than those with 30 min interval.

Abstract:Base on the cross wavelet and wavelet coherence transform methods,by using the daily averaged data derived from the NCEP/NCAR reanalysis dataset and interpolated outgoing long wave radiation(OLR) data provided by the National Oceanic and Atmospheric Administration(NOAA),the abnormal activities of the West Pacific subtropical high during the summer of 2006 and its time-delayed phase characteristics with the East Asian summer monsoon system are analyzed.The results show that the cross wavelet and wavelet coherence spectrum of the subtropical high index and the characteristic indices of East Asian summon monsoon system members can reveal the time-frequency characteristics and delayed correlation between those different factors and the subtropical high index on 14—20 days time-scale.The Mascarene high and South Asia high may predict the westward extension and northward advance of the subtropical high better;the strengthening and northward movement of ITCZ and the subtropical jet stream are synchronized with the northward jump of the subtropical high ridge;the northward advance of the subtropical high favors precipitation in Southern China,in turn,the formation of rainfall belt benefits the further westward extension of the subtropical high.

Abstract:Using the PMS data of a precipitation process in Changchun on 5th July 2004,combined with synoptic charts,satellite cloud photographs and radar echoes,this paper comprehensively analyzes the microphysical structure features of the precipitable cloud system impacted by weakened tropical cyclone Mindulle(2004).The results show that the vertical macro-and micro-structure of precipitable stratiform clouds can be partitioned into four growth layers:near the cloud top is the nucleating and depositing layer;between-4 and-7 degree centigrade is the active growth layer of cloud drops and ice crystals;from 0 to-4 degree centigrade is the layer of solid particle aggregation and cloud drop evaporation;below the zero temperature level is the layer of rain drop coagulation and the condensation growth of cloud drops.Around the melting layer,the peak value of mean diameter,maximum diameter and peak diameter of 2D-P precipitation particle were concentratedly observed to be corresponding with radar bright band echo.It is found that density distribution function N(r)=mr^fexp(-ar+br²-cr³) is able to describe the size distributions of small cloud drops,big cloud drops and raindrops in the warm layer,and the fitted spectrum distribution is well matched with the observed one,and the fitted mean diameter,square-root diameter,number concentration,and liquid water content are also close to the observational results.

Abstract:The NCEP/NCAR reanalysis data have been used to study differences between the Somali jet and the cross-equatorial flow at 105°E in association with the Asian summer monsoon variations.The results demonstrate that there are significant differences in periodicities as well as the time of climatic jumps of the interannual and interdecadal variations between the two cross-equatorial flows.The strong negative correlations are found between the two cross-equatorial flows in some decades.The Somali jet is closely related to the subsystems including the Indian summer monsoon,East Asian subtropical summer monsoon and South China Sea summer monsoon in the Asian summer monsoon regimes.However,the cross-equatorial flow at 105°E is only closely related to the South China Sea summer monsoon variations.The two cross-equatorial flows are found to have different influences on the circulation changes related to different members of the Asian summer monsoon system.

Abstract:Using the NCEP/NCAR reanalyzing data and monthly rainfall data at 160 stations in China from 1951 to 2002,this paper analyzes the influence of the variation of Mascarene high(MH) on Meiyu in the Changjiang-Huaihe basin from 1951 to 2002.Results show that MH in April-May impacts Meiyu precipitation in the Changjiang-Huaihe basin most.There is a strong positive correlation between Mascarene high in spring and Meiyu precipitation in the Changjiang-Huaihe basin,while there is a close correlation between MH in spring and atmospheric circulation systems in summer.When the April-May MH is stronger,the East Asian summer monsoon is stronger,and the Western Pacific subtropical high tends to be intensified with a more southwestward position which result in more rainfall in the Changjiang-Huaihe basin,and vice versa.Further analysis indicates that the influence of MH is stronger in the south of the Changjiang-Huaihe basin than in the north.The results are of benefit to the prediction of Meiyu precipitation in the Changjiang-Huaihe basin.

Abstract:Using the NCEP/NCAR reanalysis data and the CPC(Clinate Prediction Center) SST data of the Nino3-4 region in 1950—2003,the relation and its interdecadal variation of the ENSO and the Northern Hemispheric atmospheric circulation in winter are studied.Results show:1)the response of the Northern Hemispheric atmospheric circulation to ENSO abruptly changed in the winter of 1978/1979;2)after the abrupt change,the association between ENSO and the middle-upper level atmospheric circulation over the low latitudes has been weakened,especially over the Southeast Asia,while that with the lower-level circulation enhanced;3)the atmospheric circulation in the Eastern Hemisphere has been less affected by ENSO than before,while that in the Western Hemisphere more intensively affected.

Abstract:Using the daily average temperature data from China Meteorological Administration and the NCEP/NCAR reanalysis data,we have analyzed the features of summertime low temperature events in the southern part of China,especially in the middle and lower reaches of the Yangtze River,and the related circulation changes from 1960 to 2004.Our results show that summer temperature trend change its sign in the late 1970s;the temperature was lower than normal before the late 1970s and higher after that time.The low temperature events occurred more frequently over the south of the Yangtze River.Both the general circulation changes at different levels and variations of the precipitation along with the total cloud cover were responsible for the formation of low temperature events during boreal summer season.

Abstract:Effects of Eurasian snow cover anomaly on storm track is studied in this paper by the singular value decomposition(SVD),correlation analysis and composite analysis of the 23 winters’ 500 hPa filtered potential height variance over the north Pacific storm track region and the Eurasian snow cover data.And the possible influencing mechanism is also discussed.It is shown that the positive Eurasian snow-cover’s area anomaly leads to the southward shift and weakening of Pacific storm track,and vice versa.Deep investigation shows that the anomalous cooling of Eurasian snow cover gives rise to changes in the upper lever geopotential heights over the Eurasian continent and its downstream Pacific ocean,then the East Asia jet steam and baroclinicity,and finally the storm tracks.

Abstract:A series of severe convective storms affected Guangdong Province and produced disastrous heavy rain in Guangzhou especially on August 11,2004.This paper introduces the elementary formation mechanisms for clear air-echo before severe convection and trys to extract the dissipation rate of turbulent energy ε from the spectral data of CINRAD/SA in Guangzhou.The results show that the turbulence energy dissipation rate in the low atmosphere layer obviously increased before the severe convective storms occurred,which reveals the precursory character of this weather phenomena.

Abstract:Based on T213 data and conventional observation data,a dense fog occurring in North China plain between 19th—21st,November,2005 was simulated by using mesoscale model MM5.Results show that the heavy fog is a radiation fog occurring in stable synoptic situation.The location,intensity,formation and dissipation of the simulated fog are in accordance with the real situation.The inversion layer and abundant moisture play an important role in the maintenance of the fog.Diagnostic analysis indicate that:the fog area locates in weak vapour convergence area;the descending movement accaused by the divergence and negative vorticity above 900 hPa contributes to the formation of the inversion layer;the cold advection is also favourable for the formation of the inversion layer;the long wave radiation cooling is a predominant factor for tempereture decresing;and the short wave radiation plays an important role in the fog dissipation and diurnal variations of the fog.

Abstract:Based on the NCEP/NCAR reanalysis data during 1948—2002,the climatic distributions of summer and winter atmospheric heat sources are computed and their interdecadal variabilities analysed.Results show that there were four major atmospheric heat source centers and their positions changed seasonally.In summer,they located in central Africa,the Bay of Bengal,the Philippines/tropical western Pacific and the southwest Caribbean Sea,while in winter,they moved to South Africa,the Oceanic-Continent to the tropical Indian Ocean,northwest Australia to the tropical South Pacific and northern South America,respectively.The intensities of summer heat sources in the four major center areas all showed obvious interdecadal variations with an abrupt weakening in central Africa in 1972,an abrupt strengthening in the Philippines/tropical western Pacific in 1972 and in the southwest Caribbean Sea in 1975,and a generally weakening trend in the Bay of Bengal.In winter,the intensities of heat sources in the four center areas also showed obvious interdecadal variations with an abrupt strengthening only in northern South America,and a generally strengthening/weakening trend in South Africa and the Oceanic Continent to the tropical Indian Ocean/northwest Australia to the tropical South Pacific.

Abstract:With the summer rainfall data from 13 stations in Jiangsu from 1960 to 2000 and the NCEP/NCAR reanalysis monthly data,characters of summer precipitation in Jiangsu and its relations with Pacific SSTA(sea surface temperature anomaly) are investigated.Conclusions are as follows:obvious interannunal variations can be seen in summer precipitation,and the interannual precipitation change is positive.During flood(drought) years there was "+-+"("-+-")anomaly pattern at 500 hPa height field from low to high latitudes over East Asia.Correlation between summer precipitation and the index of East Asia monsoon is negative.Positive correlation was found between the north Pacific SSTA in the preceeded winter and the summer precipitation in Jiangsu,also between the eastern equatoral Pacific SSTA in the spring and the summer precipitation.

Abstract:Based on the synoptic analysis for a heavy rain event occurred in Shanxi on 1—2 July 2005,using the new generation mesoscale model of Weather Research and Forecasting(WRF) with two-way nested grid,the numerical simulation of the rain event is performed in this paper,and high spatial and temporal resolution model outputs are used to diagnose the relation between removal entropy index and rainfall area.Diagnostic results show that the event is caused by active subtropical high;the rainfall area matches well with the mid-low level convergence and the upper-level divergence,and the the SW low-level jets provide vapor and motive terms and play an important role in the heavy rain event.Results also show that the negative entropy change(I_RE<0) area corresponds to the large-scale heavy rain area;the convergence of the negative entropy change indicates the location of heavy rain;and the removal entropy index match the heavy rainfall centers quite well.

Abstract:By using 1950—2005 global land monthly precipitation,statistical relationship between precipitation over Northwest China during March to September(R_m) and ENSO was analyzed.Results show that the relationship of less R_m in Northwest China in the El Nino year and more R_m in the subsequent year existed stably,and with global warming,this relationship has become more stably.Northwest China,especially its east part,is the area where R_m is closest and most stably related to ENSO compared with other main arid and semi-arid areas in the latitude band of Northwest China.Northern China is the only region among the arid and semi-arid regions in the Northern Hemisphere where R_m is less in the El Nino year and more in the subsequent year.There is less/more R_m in the El Nino/subsequent year over the east part of Northwest China,while more/less R_m in the El Nino/subsequent year in the west part south of 38°N,and thus obvious difference exists between the east and west part of Northwest China.

Abstract:Based on Doppler radar and NCEP/NCAR reanalysis datasets,mesoscale characters of the ocean-effect snowstorm in the north coastland of Shandong Peninsula south of Bohai sea in the December of 2005 is diagnostically analyzed by RAMS4.4.The results show that the snowstorm occurred with the northwest airflow,large sea-air temperature differences and the special hill topography.Long life cycle adverse wind regions in Doppler radial velocity images were observed during the snowstorm.Results of numerical simulation indicate that the RAMS can successfully simulate the location and evolution of the ocean-effect snowstorm in the coastal area.The mesoscale vertical circulation is found when the snowstorm occurs,and the snowfall increases with the strengthening of updrafts and the development of adverse wind regions.

Abstract:Mesoscale numerical model MM5(V3.6) is used to simulate a heavy storm rainfall event on 16th—17th June 2003 in the Low Latitude Plateau region of China,and orographic sensitivity experiment is also performed.Analysis indicates that the water vapour which contributes to the storm rainfall has different channels at different levels.Convergence on lower layers and weak divergence on upper layers is the factor which leads to the formation of storm rainfall of M_βCS.Strong potential equivalent temperature gradients on 700—500 hPa levels accumulate and rapidly release intensive unstable energy,giving rise to the formation of upper level warm core and the lifting of isobaric surface,and the genesis of β-mesoscale cyclonic disturbance at 500 hPa.Then the lower level convergence and the upper level divergence strengthen further.The lifetime of warm core structure of M_βCS in the Low Latitude Plateau region is shorter than that in downstream regions,which is the main reason why the lifetime of M_βCS in the Low Latitude Plateau is relatively short and the precipitation intensively breaks out in a short time.

Abstract:This paper analyzes the characteristics and primary reasons of interannual and monthly variations of dust deposition in Shanghai on the basis of monthly dustfall and meteorological factors from 1993 to 2003.The interannual variations of dustfall showed a declining trend while monthly variations displayed a bimodal distribution.Synoptic backgrounds of dust deposition were classified into A,B,C,D and E types with different dustfalls by the method of clustering.Type A has the highest amount of dustfall.The closest related meteorological factors of Type A are orderly the frequencies of southerly winds and wind speed greater than 3 m/s,evaporation,and temperature;the next is precipitation,rain-days and moderate humidity;and the last is air pressure.In winter,positive correlation relationship between precipitation and dustfall is evident.

Abstract:The mass-transfer performance of hydrophobic PP(polypropylene) microporous membrane and activated MDEA(methyldiethanolamine) solutions in the CO₂ separation from a mixture was evaluated with a membrane based gas absorption coupling.Effects of gas and liquid flowrates as well as absorbent and feed components on overall mass transfer coefficient were investigated.Overall mass transfer coefficient Kov was theoretically calculated based on the model of resistance in series.Results show that,activated MDEA solutions could enhance mass transfer and increase the values of K_ov.The values of the model are in good agreement with those of experiments.

Abstract:This paper reviews the topics and recommendations of the tenth WMO Symposium on Education and Training(SYMET-Ⅹ).The theme of the SYMETⅩ is meteorological and hydrological education and training for disaster prevention and mitigation.Three topics,namely,"Preparedness—Prevention and Early warning","Mitigation — Emergency,Relief and Rehabilitation" and "Interdisciplinary training" were intensively discussed.Scientists stressed that the application of the ensemble weather prediction is of crucial importance in the estimation of the risk of the extreme weather and climate events.At the same time,meteorologists and hydrologists must be trained to use probabilistic weather forecasts.The monitoring,prediction and warning of natural disasters in China have been scaled up from simply providing disaster information to the socioeconomic benefit-related disaster service,taking into account both natural and economic factors.The interdisciplinary training which integrates management and meteorology elements may be more effective for the training of meteorologists and hydrologists in risk and crisis management.The recommendations of the SYMET-Ⅹ include the improvement of the capability of the training units in WMO Regional Training Centres(RTCs) and National Meteorological and Hydrological Services(NMHSs),the guidance of the training courses on the risk management of natural disasters mainly by providing training units of disaster prevention and mitigation,and emphasis on the requirement of the NMHSs in the training of the management and communication.