Abstract:The observational temperature data(July-August,JA)from 1961 to 2004 in East China have been used to analyze the interannual variations of regional summer temperature anomalies related to the hot summer events in the present article,and the descending trend of the summer temperature has been found.Three criterions for defining hot summers have been set up,and 10 hot summers in the recent 44 years have been indentified.The JA mean temperature field in East China can be divided into three subdivisions with the rotated empirical orthogonal function(REOF) method.The analyses of the climatic catastrophic features as well as periodicities for each subdivision show that there are no significant temperature changes in these subdivisions except the northern subdivision where summer temperature has obviously increased in the 21st century.The periods of both 2 yrs and 3-4 yrs are found to dominate in any one of the three subdivisions.

Abstract:Based on the fact that there exists significant negative correlation between summer temperature and precipitation over the southeastern China,a drought index is appropriately constituted.Choosing monthly mean sea-surface temperature,500hPa height in the Northern Hemisphere,surface temperature over the Eurasian continent from the NCEP/NCAR reanalyses as predictors,the summer drought index calculated from the monthly mean precipitation and temperature of 160 stations in southeastern China collected by Beijing Meteorological Center,are predicted with ensemble canonical correlation(ECC) method.The results show that the ECC analysis is superior to the single factor canonical correlation analysis(CCA) in the spatial/temporal correlations between observed and predicted summer drought index fields,and the superensemble mean method has higher overall skill than the equally weighted ensemble mean method.

Abstract:Using the radiosonde and surface observation data,NCEP/NCAR reanalysis data and FY-2C satellite cloud images,the extratropical transition of typhoon Matsa is analyzed by means of mesoscale Barnes filtering and physical variable diagnosis.The evolution of Matsa after landfall and the process of Tianjin and Beijing's precipitation are simulated for 60h by the Penn State NCAR nonhydrostatic mesoscale model(MM5).The results show that during the landfalling ing and northward going process of Matsa,the cold air in its northwest side first rotated along the typhoon circulation from the north to the south,and then intruded northward from the south into the warm center of Matsa gradually,and at the same time in the vertical direction there were cold airs systematically/slantly descending from the middle-upper troposphere and intruding into the typhoon circumfluence at the low level,which at last resulted in the extratropical transition of Mstsa.The cloud system of Matsa split into the west part and east one,when Matsa appoached to North China,and the emergence and development of the westside cloud is close connected with the genesis of the mesoscale convergence line at 850hPa stream field,in which the clod air took part important role.

Abstract:The adjoint assimilation of GPS precipitable water into mesoscale model MM5 and numerical simulation are conducted for the process of a heavy rain occurring in the Beijing,Tianjin and Hebei area between 23 and 24 July 2005.The effects of the adjoint assimilation is examined using 24-hr precipitation TS scores,and the RMSE between simulated and observed humidity,temperature,height and wind fields.The results prove that the assimilation of GPS precipitable water not only improved humidity field but also ameliorated temperature field,height field and wind field to different extent.

Abstract:Using the NCEP/NCAR reanalysis and in situ precipitation daily data in 2003,association of 30-70d oscillations with the heavy rain over the Changjiang-Huaihe River Valley in the summer of 2003 has been studied in the present paper.The results show that the 30-70d oscillations had important contributions to the total precipitation in the summer of 2003.The low frequency circulation showed a baroclinic structure with the positive vorticitiy in the lower troposphere,and the negative one in the upper troposphere during the torrential rain period,and 850hPa positive vorticity was systematically transported northward and westward.The positive anomalies of precipitation over the Changjiang-Huaihe River valley were strongly influenced by the low frequency wave propagations(P-J)over the west and northwest Pacific regions.Water vapor fluxes vertically integrated from the earth surface to the top of the troposphere on the 30-70d time scale indicate that southwestly monsoon wind along the edge of the western Pacific subtropical anticyclone was responsible for the water transport,and the moisture is found to be transported from the South China Sea other than either the Bay of Bangle or the west Pacific.

Abstract:The phenomenon that there exists obvious difference in times of hail shooting between the eastern and western side of the Yachi River is first revealed using observational data,and the difference is found to be associated with down-slope wind,mesoscale leeward slope low-pressure and environment heating.The reason of lake surface high wind and the range-height indicator(RHI) echo character of hail shooting over the Dongfeng lake area at river confluence reaches are analyzed.The echo analysis of the motion and evolution of two hail storms on May 10,2004 in the Yachi River basin shows that storms with multiple convection centers of small scale exhibited different development trends when crossing the river at different river reaches,and hail storms always moved along a route advantageous to their development.This may prove the mechanism for the motion and evolution of hail storms in the Yachi River basin.

Abstract:A severe snow storm on 3th December 2005 in the Shandong Peninsula is simulated with a mesoscale model MM5V3.6,and detailed diagnostic analyses are performed upon the mesoscale gravity-wave(MGW) event.The nonlinear balance equation(NBE) is used to diagnose the flow imbalance,and analysis indicates that the important role of the geostrophic adjustment and topographic forcing in the gravity-wave event in the snow storm.The MGW's wavelength is about 100km,and the propagation speed is about 20m/s.The Taihang Mountains and the flow imbalance are the key factors to initiate the MGW,on the other hand,the thermal forcing of the ocean in winter is also important in the genesis of the local snow storm.The NBE diagnostic shows clear evidence of the MGW initiation region and the propagation direction.The analysis on wave structure and maintaining mechanism suggests that the MGW in this snow storm satisfies the necessary conditions for wave ducting and Wave-CISK.This complex sequence of nonlinear interactions produced a long-lived,large-amplitude gravity-wave that created hazardous winter weather in Shandong Peninsula.

Abstract:In this paper,a genetic algorithm(GA)-based four-dimensional variational data assimilation(4DVAR) is applied to the MM5 model.In order to verify the performance of the GA assimilation system,the output of the GA based 4DVAR model has been compared with that of an adjoint 4DVAR model.The results indicate that the new method of GA-based 4DVAR can be considered as one of the effective methods to improve numerical weather prediction initial field and raise the prediction accuracy of physical field and rainfall.The new method shows a better performance than the adjoint counterpart based on the present experimental case.

Abstract:Interaction along with its interdecadal variation between tropical Pacific and Indian Ocean have been studied on the basis of the monthly NCEP/NCAR Reanalysis dataset,and GISST data.The results are summarized as follows:when Dipole indices lead Nino3 indices by 2 months,their correlation is the best,and when Unipole indices lag Nino3 indices by 3-4 months,their correlation is also the best.Indian Ocean Dipole is able to influence occurrence of El Nino to some degree,but the occurrence and development of El Nino can influence occurrence of Indian Ocean Unipole.There was an obvious jump in interaction between Dipole and ENSO events in 1961,the possible cause is likely that the impact of the Dipole on zonal winds over the tropical Pacific was weak before 1961,however enhanced after 1961.But the correlation of Unipole and ENSO events was always distinct,and their interaction has not obviously changed.

Abstract:Using the NCEP/NCAR reanalysis data from January 1 to December 31 on 2000,the wind energy of Jiangsu Province was simulated by the Regional Climate Model3(RegCM3).The comparative analysis of the simulated and observed data demonstrates that the spatial distribution of simulated wind field can well reflect the spatial pattern of the observed,and especially,the fine resolution simulation can more realistically reproduce the feature of winds over special terrains.The results of wind simulation show:1)The surface mean wind energy density of Jiangsu increases with height from 60-100W/m² on the ground surface to 320-380 W/m² at the height of 200m.2)The wind energy near the coast is larger than that in the inland,and the wind power in the central-south of Jiangsu than that in the north.Moreover,the availability of wind power above Taihu Lake and other lakes is more sufficient than nearby lands.3)The gradient of wind power is sharp between land and sea at the lower levels,while it becomes gentle at the higher levels.As a result,this paper suggests that the best location for building wind power stations is the coastal regions in the central-south of Jiangsu Province.

Abstract:Based on the kastrov expression,the calculative method of the possible sunny day total and direct radiation received by wall surfaces with different orientations was obtained.Using vapor pressure to fit the parameter of expressions,we calculated the hourly solar radiation amount received by wall surfaces with different orientations at 704 stations of China,and analyzed its variations.The distribution of radiation exposure in the strongest hourly radiation over China was also analyzed.Results show that the sunny day solar radiation amount received by southern walls increases with latitude in winter and it is the largest among those recieved by walls with different orientations;and variations of the sunny day solar radiation received by eastern and western walls with latitude are relatively smaller than other orientations and its radiation amount is the largest in summer.

Abstract:Aerosol optical depths(AOD) were retrieved by using the vapor pressure and visibility data over 70 stations in China from 1999 to 2003,then its statistical characteristics were analyzed.It is found there Sichuan Basin was the maximum area of yearly mean AOD,and another two large value centers were in the middle and lower reaches of Yangtze River and the coastal area of Guangdong,but AOD was lower in the Northeast China and Northwest China and Yunnan.The distribution of AODs for each month was similar,but differences were also obvious.During 1999-2003,the national average AOD showed a weakly increasing.The monthly average AOD had a close negative correlation with visibility.

Abstract:A heavy rainstorm happened in North China during the period from 0000 UTC 16th to 0000 UTC 17th August 2005,and the strongest rainstorm occurred in Tianjin.By use of surface observation data and NCEP/NCAR reanalysis data and results of the mesoscale numerical model MM5V3.7,the circulation features and heavy rain in North China during 16th to 17th August 2005 were diagnosed and analyzed.The results show that the dry cold air intrusion had important impact on the rainstorm.The dry air in the upper troposphere intruded into the lower level was in favor of the development and enhancement of the meso-scale cyclone.

Abstract:The pot experiment was conducted to study the effect of lead,especially at low levels,in Nanjing and Beijing soils on the growth of Brassica campestris SSP.chinensis Makino.Results show that the texture of soil and lead pollution had effects to a certainty on the growth of Brassica campestris SSP.chinensis Makino.Lead content in plant presented an increase-to-decrease trend with the rising concentration of soil lead.Under the treated concentration of lead at 100 mg/kg,the growth of Brassica campestris SSP.chinensis Makino was inhibited and the content of lead in the plant was higher than control groups.

Abstract:Based on the data observed by airborne particle measurement system(PMS) under the condition of clear sky weather in summer over the Hengshui lake area,the distributive characters of aerosols have been analyzed.The results show that the size of aerosol particulates over Hengshui lake is smaller than those over Hengshui city and Zaoqiang town,and the size over the Hengshui lake area most ranges from 0.1 to 0.25 μm,and very a few from 0.25 to 3.0μm.As for the number concentration of aerosols,the concentration at the low level over Hengshui lake is larger than those over the city and town,but rapidly decreasing with height,and at the middle-upper level it is smaller over Hengshui lake than those over the city and town.The aerosol characteristics and vertical distribution over the lake different from those over the city and town.

Abstract:On the basis of the Meiyu characteristic variable data at 37 stations in the Changjang-Huaihe River Valley from 1954 to 2001,the temporal evolution and spatial distribution of Meiyu characters are investigated in terms of harmonic analysis,empirical orthogonal function(EOF) and maximum entropy spectrum analysis and so on.Results show that temporal-spatial distributions of Meiyu characteristic variables are not homogeneous in the Changjiang-Huaihe River Valley.There are prominent interannual quasi-three years and interdecadal(10 years) variabilities in variations of Meiyu characteristic variables,and there are also positive or negative correlations between those interdecadal variations.The duration,rainfall and rainfall rate of Meiyu are positively/close correlated(P<0.001) and except the onset date,the end date,rainfall and duration of Meiyu all showed an increasing long-term trend.

Abstract:Based on daily maximum and minimum temperature data of 234 stations in China during the period of 1955-2005,the spatial and temporal features of trends of annual and seasonal extreme temperatures are studied by using modern statistical diagnostic methods such as the computation of trend coefficients.Results show the stably increasing trends of annual and seasonal extreme minimum temperatures all over China.Decreasing trends of extreme maximum temperatures are obvious in the lower reaches of the Yellow River in year,spring and summer;while increasing trends of extreme maximum temperatures are evident in South China.Increasing trends of extreme temperatures are detected in most areas of China,and the increase range of extreme minimum temperatures is greater than that of extreme maximum temperatures.Increasing trends of extreme minimum temperatures are found in every season,especially in winter.Further analysis suggests that interdecadal variations in extreme maximum and minimum temperatures are generally consistent.

Abstract:Based on the April temperature data of 20 surface meteorological stations of the Beijing region from 1990 to 2004,the characteristics of Beijing spring urban heat island(UHI) were analyzed.The results show that the UHI in the nighttime was stronger than that in the daytime.Furthermore,with the additional data from three automatic meteorological observing stations and the 325m meteorological tower of LAPC(State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry),the characteristics and influencing factors of a strong UHI event on 18th-19th April 2003 were analyzed.And the results show that the strong UHI event occurred in the nighttime of 18th,and its centre lay over major urban area along the Baijiazhuang-Tian'anmen-Gongzhufen area,it weakened and disappeared in the next daytime,and the diurnal change of the strong UHI was very obvious.In the clear night of sunny day on 18th,the surface wind speed over the urban areas and the suburb was very small(≤1.0m/s),and the wind speed below 15m in the surface layer remained weak(≤1.5m/s),and the strong inversion in the atmosphere layer below 320m maintained all the night,and all of these contributed to the formation and maintenance of the strong UHI.And in the next daytime the solar radiation had most important effects on the weakening and disappearance of the strong UHI,it made the suburban surface atmosphere temperature rise faster and more than the urban atmosphere temperature and the urban surface inversion temperature as well as strong UHI disappear in the end.

Abstract:Using the super-sub-solution method and the maximum principle,the existence result of positive classical solutions for a singular semilinear elliptic Dirichlet problem is obtained.We also establish the regularity of classical solution to the problem(1).

Abstract:It is important for the study of the atmosphere-vegetation interaction to extract architectural parameters rapidly and accurately.In this paper,the methods for leaf area index(LAI) and leaf angle distribution(LAD) retrieval areaddressed from the following three aspects:the theory and model of canopy structure parameters extraction,the retrieval of gap fraction,and clumping index.And the main factors affecting the retrieval accuracy of canopy parameters in the collection and analysis of fisheye photographs and model's hypothesis etc are also ananyzed.It is worth pointing out that the hemispherical photography is an ideal indirect LAI and LAD estimation device,while errors from digital hemispherical canopy photography could not be avoided,therefore,parameter validation should be performed to delete the uncertainty in retrieval results.