Current Issue

• Distribution, Changes of Atmospheric Precipitable Water over Qinghai-Xizang Plateau and Its Surroundings and Their Changeable Precipitation Climate
• CAI Ying;QIAN Zheng-an;WU Tong-wen;LIANG Xiao-yun;SONG Min-hong
• 2004 Vol. 23 (1): 1-10. 
• Abstract ( ) PDF (518KB) ( )
• In this paper, the multiyear mean features and their seasonal, yearly and interdecadal changes for the air column precipitable water (hereafter PW) over the Qinghai-Xizang Plateau and its Surroundings (QXPS) have, wholly, not partly, been analyzed, utilizing the NCEP's monthly mean specific humidity, wind velocity and potential height reanalyzed gridded data and the observed rainfall data etc.The results show that there exist the considerably regional, seasonal, yearly and interdecadal changes of the air column PW over the QXPS.Over the QXPS there are the maximum PW over the South and East Asian Monsoon regions, with the value of 60mm or more in summer; the minimum PW over the Qinghai-Xizang Plateau (QXP), with only 3mm in winter.In East and South Asian Monsoon areas have the largest summer and winter seasonal changes of the PW, the PW values summer are four times as large as those winter.In recent four decades the air column PW over the North China and east part of Northwest China are continually being decreased; but has something increase tendency over the Changjiang river reaches and to the south of it since 1980's, namely with the distribution pattern of drying in the north and wetting in the south in China.On the other hand, there are the striking differences in the PW conversion rate into precipitation in various parts of China summer, with the highest rate in QXP, the second highest in East Asian Monsoon areas, the minimum one in south Xinjiang.

• Precipitation Field of Large Scale Catchment Reconstructed by Combination of GMS Satellite and Weather Radar
• Ahmed Tidiane Diallo;LIU Xiao-yang;MAO Jie-tai;ZHU Yuan-jing
• 2004 Vol. 23 (1): 11-17. 
• Abstract ( ) PDF (303KB) ( )
• For a large basin where a ground weather radar cannot cover completely, the precipitation field could be better estimated by radar-modified satellite data than satellite data alone.A method for 3 h precipitation estimation is first presented based on GMS satellite and gauge data statistics.Then the estimation of precipitation is further modified by ground weather radar and Kalman filter.The result on test subcatchment in Shihuaihe river basin shows that the error of satellite precipitation estimation decreases from 31% down to 13% after the radar adjustment.

• Predictability Analysis and Preliminary Application of the Bay of Bengal Summer Monsoon Onset
• DUAN An-min;MAO Jiang-yu;WU Guo-xiong
• 2004 Vol. 23 (1): 18-25. 
• Abstract ( ) PDF (336KB) ( )
• Based on thermal-wind relation and the fact that the essence of summer monsoon onset is a result of the change in land-sea thermal contrast, the relation between monsoon onset and the variation of the subtropical anticyclone is studied.The summer monsoon onset appears firstly over the eastern Bay of Bengal (BOB), then propagates regularly eastwards to the western Pacific by early June.Whenever the axis arrives at a region, the in situ lower-layer wind direction and the sign of meridional temperature gradient (MTG) in the upper-layer are changed, and monsoon onset occurs.Furthermore, the time required to overturn the MTG depends on the initial MTG as well as the averaged meridional differential heating before the monsoon onset.Based on these results, the daily and monthly NCEP/NCAR reanalysis data during March to May 1980-1999 were used to explore the predictability of the BOB monsoon onset.Results show that qualitative prediction of the BOB monsoon onset is possible by using the initial MTG and the climate mean meridional differential temperature variations.Moreover, there is significant correlation between the spring-time monthly-mean air temperature over Qinghai-Xizang Plateau and the BOB summer monsoon onset.This provides additional clue for predicting the monsoon onset.These two methods have been utilized to predict the qualitative BOB monsoon onset in 2000 and 2001 correctly.However, detailed examination reveals that a satisfactory prediction of the BOB monsoon onset requires the consideration of the low-frequency variability of the atmospheric circulation.

• Study on Influence of Electrical Processes on Dynamical Development in Thunderstorm
• SUN An-ping;ZHANG Yi-jun;YAN Mu-hong
• 2004 Vol. 23 (1): 26-32. 
• Abstract ( ) PDF (298KB) ( )
• The influence of electrical processes on dynamical development was calculated by using a three-dimensional dynamics and electrification coupled model.The results revealed that the triple electrical structure was formated with the development of simulated thunderstorm.The direct effect of electric field force on development of thunderstorm was smaller than that of dynamics.The vorticity that electric field force produced was 10 ^-6·s ^-1 and 2 orders smaller than that of dynamics.However, the electric field force influenced the microphysical processes, especially the falling velocity of hydrometeors.The electrical processes changed the temporal and special structures of hydrometeors distribution by adjusting the transformation between hydrometeors.By this way, the water vapor increased by 41% and the latent heating increased by 19.4%.The structure of stream field was changed and electrical vorticity was about 10 ^-4·s ^-1.It corresponded to that of dynamics.Therefore, there was a large influence of electrical processes on development of thunderstorm in mature stage of thunderstorm.

• Measurement of Column Cloud Liquid Water Content by Airborne Upward-Looking Microwave Radiometer (Ⅱ): Retrieval Method
• JIANG Fang;WEI Chong;LEI Hen-chi;JIN De-zhen;ZHANG Jing-hong;GU Shu-fang
• 2004 Vol. 23 (1): 33-39. 
• Abstract ( ) PDF (274KB) ( )
• The fundamental and method of deducing path-integrated cloud liquid water content (L) by an airborne upward-looking microwave radiometer are introduced in this paper.Based on historic radiosonde data in Changchun city, Jilin province and on the model of vertical distribution of cloud liquid water content for typical stratiformis, the coefficients of retrieval equation are obtained as the functions of height for each month from April to July and the numerical simulation tests of the accuracy of retrieval results are given: The statistical relative deviation of retrieved values of L to the simulated trues on the ground is 15%~25% and that at altitude of 6 km is 5%~10%, that means the retrieval method and implementation of the method are applicable to processing measurements of an airborne radiometer made in China recently.Besides, the information on actual height of the lowest cloud base is used in constructing of cloud liquid water profile by using the radiosonde profiles, that makes an improvement of relative accuracy of retrieved value of L at almost all altitudes by 5%~10% according to numerical simulation comparison.The lower the altitude is, the more the accuracy is improved.

• Echo Structure for Splitting Process of A Long Life Cycle Thunder Cloud
• ZHANG Hong-fa;ZUO Hong-chao;CHENG Chen-pin;GUO San-gang
• 2004 Vol. 23 (1): 40-47. 
• Abstract ( ) PDF (475KB) ( )
• In studying the evolvement rule of severe hailstorm in Pingliang region, it is found that the severe local hailstorm on 13 August 1976 is a long life thunderstorm produced splitting process which form the supercell hailstorm having the leftward- and rightward-movements.Combining the sounding data and environment wind field, the echo characteristics of hailstorm produced splitting process were analyzed.The results show that, in the strong wind shear environment, the observed environment wind velocity 07:00 and 19:00 increases with hight, their u and v wind components appear opposite correlation, and also increase with hight.The calculated environment wind vector by the numerical model has weak anticyclonic rotation at 1~3 km hight, has the strong anticyclonic rotation at 4~8 km, and has the strong cyclonic rotation above 8 km, showing the thunderstorm produced splitting process has strong shear and wind velocity increased with height.After splitting, the leftward- and rightward- moving supercell hailstorms are to maintain and develop by itself, and generat the hail shooting.The evolution process in the whole thunderstorm is to maintain a long life cycle, the echo characteristic has four different stages.

• Numerical Experiments on the Effects of Lateral Boundary Topographic Buffer Zone in Regional Climate Model
• ZHONG Zhong;SU Bing-kai;ZHAO Ming;TANG Jian-ping
• 2004 Vol. 23 (1): 48-54. 
• Abstract ( ) PDF (325KB) ( )
• The regional integrated environmental model system (RIEMS) is used to test the effects of lateral boundary topographic buffer zone on the simulation of climate in East Asia.The results suggest that the root-mean-square error between simulation and observation is decreased when the regional model is conducted with the topographic buffer zone, and so does the meso-scale kinetic energy in model domain, which would be benefit for the long-range integration of regional model.It also shows that the quantitative precipitation simulation is improved with the buffer zone, whereas there is no significant change in precipitation scenario, especially in northern part of China.

• Analyses and Numerical Simulations of Southwest Vortex Rainstorm Processes in July 2000
• JIANG Yong-qiang;ZHANG Wei-huan;ZHOU Zu-gang;ZHANG Zhi-hua
• 2004 Vol. 23 (1): 55-61. 
• Abstract ( ) PDF (343KB) ( )
• The large scale weather system of the southwest vortex rainstorm process during 1~8 July 2000 is analyzed.Also the numerical simulation of this process is conducted by a mesoscale model(MRM1).It is shown that the rainstorm process of southwest vortex is divided into two stages, corresponding to two cold air processes of moving southward respectively.Latitudinal fluctuation of warm shear line is an important factor for rainstorm.Northward propagation of southwest jet cores causes the rain area moving northward.The meso- α scale vortex and shear line are successfully simulated.Its intense inclined rising air current, mesoscale columnar structure of positive vorticity, as well as the convergence moisture flux divergence provide for dynamical and moisture conditions of the heavy rainstorm, while the energy frontal zone of the south-north orientation, the long and narrow warm moisture tongue along low-level jet axes, the rather strong middle and low level unstable stratifications are important condition of this persistent rainstorm.

• Applying Nonlinear Oscillation Theory to Evolution Law of Yunnan Local Temperature
• CAO Jie;TAO Yun
• 2004 Vol. 23 (1): 62-67. 
• Abstract ( ) PDF (252KB) ( )
• The nonlinear oscillation equations describing local temperature were applied to study the evolution law of local temperature at 17 stations in Yunnan, the specific equation was obtained from the retrieving theory and the each ten day temperature departure data during January 1958 to December 2000.According to the classical nonlinear oscillation theory, the temperature evolution law at 17 stations in Yunnan was studied.The results indicate that the local land-air system in Yunnan is weak nonlinear system, and its inherent period is from 60 to 100 days.Under no external forcing condition, the local temperature amplitude of Yunnan always decreases with time.Under external forcing condition, the local temperature amplitude of Yunnan oscillates with the oscillation of the external forcing.The future local temperature evolution patterns in yunnan were forecasted by the retrieved nonlinear oscillation equations, and its average forecasting accuracy is 78.9%, which indicate that the equations have better forecasting ability and stability.

• Relationship between South Asian High and Characteristic of Precipitation in Mid-and Lower-Reaches of Yangtze River and North China
• HUANG Yan-yan;QIAN Yong-fu
• 2004 Vol. 23 (1): 68-74. 
• Abstract ( ) PDF (383KB) ( )
• By using of the NCEP/NCAR monthly mean meteorological reanalysis data and the monthly precipitation data in China, the relationships between the South Asian High(SAH) and the precipitation of the typical drought and flood years in the mid- lower reaches-of the Yangtze River and North China are studied in this paper.It is found that the intensity and the center position of the SAH can affect the droughts and floods in the two areas.Anomalous intensifying of the SAH usually induce floods in the mid-and lower-reaches of Yangtze River and droughts in North China; while anomalous weakening of the SAH often induce droughts in the mid-and lower-reaches of the Yangtze River and floods in North China.In addition, it is concluded that the anomalies of precipitation in the two areas are usually in opposite phase.

• A Case Study on Coupling Interaction between Plateau and Southwest Vortexes
• CHEN Zhong-ming;MIN Wen-bin;MIAO Qiang;HE Guang-bi
• 2004 Vol. 23 (1): 75-80. 
• Abstract ( ) PDF (267KB) ( )
• The evolution of southwest vortex and the occurrence of heavy rain caused by the coupling interaction between Plateau and southwest vortexes during the period of 26~28 July 1982 are diagnosed.The results show that, when the Plateau vortex moving eastward near 100°E, the positive vorticity advection and the negative unbalanced force in the east part of the Plateau vortex on 500 hPa imposed on 850 hPa southwest vortex occurred the vertical superposition.The coupling interaction between both the vortexes leads to the development of the southwest vortex and the occurrence of heavy rain.

• Analysis on Distribution Character of Rainfall over Qilian Mountain and Heihe Valley
• ZHANG Jie;LI Dong-liang
• 2004 Vol. 23 (1): 81-88. 
• Abstract ( ) PDF (443KB) ( )
• Using the EOF and REOF methods and rainfall data of 42 weather stations in Qilian mountain and its surroundings, the spatial variation of annual rainfall in Qilian mountains is summarily analysed and divided three subregions.By combining grid analysis method, GIS technology, as well as aiming at rainfall distribution in the middle and east of Qilian mountains, the fitting study of annual rainfall is done and the complex variation of simulated rainfall in space is analyzed.The results show that the local rainfall distribution can be obtained by applying those methods, local rainfall and the observed rainfall at station are identical, at the same time, the terrain of Qilian mountain area can be reflected by local rainfall of grids, and its rainfall distribution provides the scientific basis for the water source distribution in Heihe valley.

• Numerical Simulation and Diagnosis Analysis of "4.12" Sand-Dust Storm
• WANG Jin-song;LI Yao-hui;KANG Feng-qin;ZHANG Hua
• 2004 Vol. 23 (1): 89-96. 
• Abstract ( ) PDF (404KB) ( )
• Using the MM5 mesoscale numerical model and the T106 analysed data, the strong wind weather type and surface wind field of the strong sand-dust storm in Gansu Corridor on April 12, 2000 were simulated.the diagnosis analyses have done by the output results of the model.It shows that the MM5 model can simulate the strong wind and ascending motion of strong sand-dust storm area, the north-west wind is appeared and the strong wind is converged distinctly at Gansu Corridor before 3 hours of the sand-dust storm outbreak.The horizontal distribution of potential vorticity has certainly indication for occurring time and area of the sand-dust storm.Strong sand-dust storm area lies below the dense strip of isometric potential vorticity at upper troposphere.The vertical distribution of helicity over the sand-dust storm area is the negative value in the upper levels and the positive value in the lower levels.There is certain corresponding relation between the evolution of the positive value of the helicity and the occurrence of sand-dust storm.

• Numerical Simulation of Mobile Emission Pollution in Urban Street Canyon
• LI Lei;ZHANG Lei;HU Fei
• 2004 Vol. 23 (1): 97-102. 
• Abstract ( ) PDF (266KB) ( )
• A simple 3-D street canyon pollution model is developed and validated by the measured data.Using this model, 7 schemes are designed to simulate the pollution condition in street canyon.The result of the CO numerical experiment shows that the wind direction and velocity above street canyon are the important factors to decide the pollution condition in the street canyon.The larger the angle between the wind direction and the street axis and the weaker the wind velocity, the higher the pollutant concentration on street surface is.In the light of current typical traffic flow and average mobile emission factors, CO surface concentration in the street of Lanzhou tends to exceed the national standard.If the traffic flow increases too rapidly, the CO surface concentration in street will likely exceed the national standard by 2008, even though the emission factors are under control.

• A Study on Remote-Sensing Inversion of Atmospheric Aerosol Particle Size Distributions of Lanzhou City Winter
• LIU Ji;CHEN Chang-he
• 2004 Vol. 23 (1): 103-109. 
• Abstract ( ) PDF (293KB) ( )
• The measured data of the aerosol optical depths in Lanzhou city winter are used to invert the columnar aerosol size distributions by inversion method.Moreover, the validity of inversion programs and the dependability of inverted results are demonstrated.Results show that the inverted columnar aerosol size distributions are all characterized by three peak modes.The optical depths calculated by directly-calculation method are used to check inversion method.Results show that the inversion programs is valid and the inverted results is correct.

• Study on SO ₂ Atmospheric Environment Capacity in Lanzhou Winter
• AN Xing-Qing;CHEN Yu-chun;Lü Shi-hua
• 2004 Vol. 23 (1): 110-115. 
• Abstract ( ) PDF (257KB) ( )
• Through numerical simulation method, the atmospheric capacities of sulfur dioxide in Lanzhou winter have been studied to offer the premise and basis for the total quantity control method, which is usualy one of the atmospheric pollution control methods.First, the concentration of sulfur dioxide in Lanzhou city are simulated with the Hybrid Particle and Concentration Transport Package Model(HYPACT), which is forced the meteorological conditions produced by a three-dimension model, the Regional Atmospheric Modeling System Version 4.3(RAMS4.3).Then, concentration-shared ratio of each pollution unit in Lanzhou is computed.Finally, using the linear programming method, the atmospheric capacities of SO ₂ of representative days in Lanzhou winter are calculated according to the atmospheric state quality standard.

• The Statistical Characters of Influencing Factors of Diffuse Irradiance on the Clear Sky Days in Dunhuang Region
• LI Ren;JI Guo-liang;YANG Wen;Lü Lan-zhi;ZHOU Xiao-ping
• 2004 Vol. 23 (1): 116-122. 
• Abstract ( ) PDF (279KB) ( )
• Using the observed solar irradiance data in whole year of 1981-1983 and the January to February of both 1984 and 1985, the variation of the diffuse irradiance on the clear days in Dunhuang region with the solar height angle, atmosphere optical mass and the aerosol optical depth were analyzed.A statistical relation was found by the last square method, it shows the variation of diffuse irradiance on clear sky days with the solar height angle coincides with power function, and the diffuse radiation on clear days increases linearly with the aerosol optical depth of atmospheric column.

• An Analysis of Atmospheric Diffusion Features in Liaodong Bay
• YANG Hong-bin;MA Yan-jun
• 2004 Vol. 23 (1): 123-126. 
• Abstract ( ) PDF (173KB) ( )
• The atmospheric diffusion features are studied using data obtained with tower-based sensors at a site located about 800 m on the coast area.The wind data measured by three axis propeller anemometer in Liaodong Bay in 1993 were used to calculate atmospheric diffusion parameters and turbulent intesity.It is shown that σ _y and σ _z are a little larger than the values from Briggs' equation under different atmospheric stability conditions, but smaller than those in Benxi; the turbulent intensity is the largest for unstable conditions(B, C).