Current Issue

• NUMERICAL STUDY OF CONDITIONAL SYMMETRIC INSTABILITY OF "96.1" SNOWSTORM
• WANG Wen;CHENG Lin-sheng
• 2000 Vol. 19 (2): 129-140. 
• Abstract ( ) PDF (467KB) ( )
• With the criteria of nonlinear symmetric instability theory,the mechanism of the heavy snowstorm of 15~17 January 1996("96.1") occurred in the northeast region of the Qinghai-Xizang Plateau is diagnosed by using the output data of a MM4 mesoscale numerical model which fairly well simulated the developing structure and the evolution of the "96.1" snowstorm,it suggested that the CSI is one of the mechanisms of triggering and organizing the shear line on which the snowstorm formed.Based on the diagnosis,numerical simulation experiments are done by nonlinear,non-zonally and non-parallel basic flow CSI models to further validate the possible effect of CSI on the formation of the snowstorm,the results showed that the circulations of symmetric perturbation fields emerged in each model,not only the fields of vertical velocity are coincident with that of streamfunction,but also with the observations,the results in the CSI is substantially a formative mechanism for the occurrence of the "96.1" snowstorm,though the vertical velocity fields are behind the shear line during the evolution.

• MESOSCALE ANALYSIS ON THE FORMATION AND DEVELOPMENT OF SOUTHWEST VORTEX DURING 8~10 JULY 1989
• ZOU Bo;CHEN Zhong-ming
• 2000 Vol. 19 (2): 141-149. 
• Abstract ( ) PDF (321KB) ( )
• By using conventional and non-conventional observation data,a preliminary study on the formation and development of southwest vortex during 8~10 July 1989 is made.The results show that the circulation evolution of the southwest vortex in PBL displays discontinuity feature in comparision with the case in free atmosphere,but the convection and precipitation in the region of southwest vortex show same feature too and the important factors that affect formation and development of this southwest vortex are the dynamical force of unbalance fields on PBL top and positive vorticity advection on 500 hPa.

• ANALYSIS OF TEMPORAL AND SPACIAL VARIATIONS FOR CLOUD RADIATIVE FORCING IN CHINA BY USING ERBE DATA
• MA Xiao-yan;JI Guo-liang
• 2000 Vol. 19 (2): 150-158. 
• Abstract ( ) PDF (386KB) ( )
• The basic characteristics of cloud radiative forcing over the continent of China are investigated by using ERBE data from 1985 to 1988.The results indicate that there are highly variable distributions among diffenrent regions and strong seasonal variation.The highest negative values of cloud forcing occur over Sichuan and Guizhou areas,next is middle or lower reaches of Yangtze River and in North China,Qinghai-Xizang plateau lies in the transition regions,while small positive values associate with the arid areas in winter over the northwest of China.In addition,cloud forcing also have some interannual variations.

• THE IMPACT OF CLIMATE VARIATION ON THE HISTORY EVOLUTION OF CHINA
• TANG Mao-cang;TANG Chi
• 2000 Vol. 19 (2): 159-164. 
• Abstract ( ) PDF (265KB) ( )
• According to the Chu's temperature vibration curve of China in the past 3000 years ^[1],it is found that the progressive stages of Chinese history are appeared in the warm periods,and the regressive stages are appeared in the cold periods.

• SOME CHARACTERISTICS OF INTERANNUAL AND INTERDECADAL CHANGES IN THE EASTERN PART OF NORTHWEST CHINA
• MA Jing-xian;DAI Cai-di
• 2000 Vol. 19 (2): 166-171. 
• Abstract ( ) PDF (217KB) ( )
• Interdecadal precipitation changes in the eastern part of Northwest China can appear obvioursly.After 1990,the region of drought enlarges,the intensity of drought intensifies and the region shifts southeastward,exhibiting much drought trend.

• APPLICATION OF PERIOD RELATION BETWEEN SAH AND WPSH TO FORECASTING SHAANXI RAINY SPELLS SUMMER
• ZHAO Gai-ying;LIU Bing;QI Shou-jin
• 2000 Vol. 19 (2): 172-178. 
• Abstract ( ) PDF (258KB) ( )
• In this paper,spectral analyses of both the oscillation index of the South Asia High(SAH) in 100 hPa and the index of extending westward of the West Pacific Subtropical High(WPSH) in 500 hPa have firstly been done.The results show that the oscillation of the SAH has mainly a quasi-biweek period;the WPSH,a quasi-week one.Usually,when the SAH moves eastward,the WPSH extends westward,the former occurs mostly one to two days earlier than the latter.Also when the periods of both the SAH and WPSH meet together,there is rainy spells in Shaanxi Province summer.

• CHEMICAL CHARACTERISTIC OF TWO DUSTSTORMS IN THE SOUTH-EAST COASTAL AREA OF CHINA AND ITS POSSIBLE ORIGIN
• CAI Chen-xia;JIANG Wei-mei;HUANG Shi-hong;LI Lian-meng;XU Zheng-tao
• 2000 Vol. 19 (2): 179-186. 
• Abstract ( ) PDF (299KB) ( )
• The proceedings and meteorological background of two duststorms happened in Changzhou on 10~14th April 1992 and in Xi'an on 14~17th April 1998 were discussed.The results show that there are chemical characteristic differences between the duststorm and non-duststorm proceeds.By comparison with the characteristics of some kinds of soils,we came to know the possible origin of the duststorm and the distributions of soil source to the duststorm were accounted.

• A MESO-SCALE ANALYSIS OF QINGHAIXIZANG PLATEAU SNOW STORM AND ITS VORTEX SOURCE STUDY
• XU Jian-fen;TAO Jian-hong;XIA Jian-ping
• 2000 Vol. 19 (2): 187-197. 
• Abstract ( ) PDF (394KB) ( )
• The synoptic chart and T63 data were used to analyse the heavy snow event in the middle of January 1996 in Qinghai Province.The result suggests that the heavy snow event was caused by the plateau's shear line on meso-αscalewhich was generated by the combination of northerly airflow areas with coldness and dryness and southerly airflow areas with warmness and humidity.The positive vorticity on the shear line was the main trigger signal.The diagnosis shows that the advection and the twisting terms were the main contribution for the high level positive changing vorticity,and the two term positive contributions were relative to the proper allocation and interaction of the westerly jets on the south and north sides over Plateau background field.

• CLASSIFICATION OF QINGHAI-XIZANG PLATEAU LANDUSE AND TWO-DIMENSIONAL NUMERICAL SIMULATION OF RADIATION FLUX ON ITS NORTHWEST PART
• CHENG Lin-sheng;SONG Zhen-xin;YANG De-bao
• 2000 Vol. 19 (2): 198-213. 
• Abstract ( ) PDF (593KB) ( )
• Trough the results of the classification for Qinghai-Xizang Plateau landuse and meridional two-dimensional numerical simulation along Wudaoliang in this paper,we found that 13 landuse categories all are existed,in spite of its vegetation exhibiting a few bands from northwest to southeast,but the landuse is still very complex.This classification of the landuse at grid points provides a quite useful surface boundary condition for high resolution numerical model and simulation in this region.The considerable closeness and consistence of the simulated and observed results for the surface net radiation flux and its components shown that this model possesses a capacity of simulating diurnal variation of surface flux in Qinghai-Xizang Plateau region.The simulated result and observed analysis also indicated that the solar net short-wave radiation was the main component in the surface radiative energy budgets under the clear sky condition during summer,its peak value 884 W/m ² is obvious greater than that of other places in our country,the single peak value interval occurred between 12:00BST(04:00UTC) and 14:00BST(06:00UTC) was consistent with the surface outgoing long-wave radiation,but it advance one hour.The diurnal variation of atmospheric downward longwave radiation and the surface net radiation,this is related to a complex variation of cloud over Qinghai-Xizang Plateau region.The mean value of single peak value of the surface net radiation was about 584 W/m ²,but their peak values exhibited obvious difference due to the different underlying surfaces.The evolution and structure of the sensible heat flux in cross section revealed a few important features.

• ANALYSIS OF RELATIONSHIP BETWEEN SNOW COVER ON EURASIA AND QINGHAI-XIZANG PLATEAU IN WINTER AND SUMMER RAINFALL IN CHINA AND APPLICATION TO PREDICTION
• CHEN Xing-fang;SONG Wen-ling
• 2000 Vol. 19 (2): 214-223. 
• Abstract ( ) PDF (395KB) ( )
• The relationships between the snow cover in Eurasia and the Qinghai-Xizang plateau(QXP) in pre-winter and the summer rainfall in China were studied and tested.The result shows that there is the impotant effect of the snow cover on the summer rainfall in China.The relationship in winter and spring snow cover with the summer rainfall are about the same.But the relationship distributions between the snow cover in Eurasia and QXP and the summer rainfall in China are nearly contrary.The main positive correlation for snow cover in QXP occurs in the mid-lower reaches of the Yangtze River and North-East China and the east region of North China and South-West China.The flood of the Yangtze River valley in summer usually is occured when anomalous snow cover in QXP would be above normal in winter.This is the important indicator for the prediction of rainfall in summer.

• THE USE OF VLF AND IF-SOUND SOUNDING SYSTEM FOR DEVELOPING AND DISCUSSING MESOSCALE CATASTROPHIC STRONG CONVECTION WEATHER(THUNDER STORMS) NOWCASTING AND WARNING SYSTEM OVER NORTHERN BAY OF SOUTH CHINA SEA
• HAN Yuan-jie;LI Shao-wen;CHEN Hong
• 2000 Vol. 19 (2): 224-234. 
• Abstract ( ) PDF (395KB) ( )
• The warning system to be composed of infra-sound sounding net and single thunder warning station by use of VLF and IF-sound emitted from lightning was developed in 1995.After that,during three years(1995~1997) the system ran on in the 4~6 months every year and forecast 21 strong thunder storms.The convection 17 m/s gale had been happened in Northern Bay of South China Sea since the IF-sound signal appeared 3~6 hours in advance.From April to June 1997,the seven catastrophic convection thunderstorms had been forecasted by the authors and had been protected by NHOC before it appeared 40 minutes ago.The nowcast decreased the loss about seventy million RMB predicted.In the strong convection weather system,the strong turbulence exists in the beginning,a lot of the vapor phase changes and water drops increase and grow up with the turbulence in the unstable cloud,and the charge accumulate or release go on,the drops grow up with collision and electric attraction again and again,turbulent and entrainment motion might be caused selforganization and positive feedback.Consequently the turbulent motion would evolute to some single direction motion(prosconvection) and then emit the IF-sound if the conditions exist for very strong extra-unstability and more moisture exchange.By the time the turbulent motions develop to the convection that can emit another long period IF-sound.The results show that the pros 1~2 seconds period IF-sound wave of the turbulence is different from 5~100 seconds period of IF-sound waves of the convection,besides,the waves pattern don't show dispersion and always appear in half amplitude form.The mechanism has been discussed.

• LYAPOUNOV STABILITY ANALYSE FOR CONVECTION BOUNDARY LAYER
• XUE Ju-kui;HU Yin-qiao
• 2000 Vol. 19 (2): 235-243. 
• Abstract ( ) PDF (316KB) ( )
• According to the dissipative structure theory and Lyapounov's stability principle,the theremodynamic and hydrodynamic stabilities of convection boundary layer are studied for a simple dry atmospheric convection model.As a result,a generalized Lyapounov founction is made,by which,the critical Rayleigh number for onset of convection in the non-equilibrium static boundary layer is given by small perturbation.The numerical experiment is in good agreement with the theoretical analyse.

• THE INFLUENCE OF TYPHOON ACTIVITIES ON DROUGHT ON NORTHEAST SIDE OF QINGHAI-XIZANG PLATEAU
• XIE Jin-nan;ZHUO Ga
• 2000 Vol. 19 (2): 244-252. 
• Abstract ( ) PDF (348KB) ( )
• An analysis was undertaken on the influence of typhoon activities on the drought and flood on the northeast side of Qinghai-Xizang Plateau.The results show there exists an obvious positive correlation linkage between the typhoon numbers and the precipitation on the northeast side of Qinghai-Xizang Plateau.

• DIAGNOSTIC ANALYSIS OF MOIST POTENTIAL VORTICITY FOR HEAVY RAIN IN MIDDLE YUNNAN
• DUAN Xu;LI Ying
• 2000 Vol. 19 (2): 253-259. 
• Abstract ( ) PDF (286KB) ( )
• By using the concept of moist potential vorticity,the characteristics of moist potential vorticity are analyzed in the process of the six heavy rain days over the middle Yunnan in June 1998.The results show that the very stiff moist isentropes and strong warm and moist air located its south can lead to the development of moist slantwise vorticity and the heavy rain occurred.The top of moist convection air can only attain between 600 hPa and 500 hPa levels.When MPV1 < 0 and MPV2 > 0,sudden heavy rain will probably happen.

• STATISTICAL RELATIONS BETWEEN TYPHOON ACTIVITY AND PRECIPITATION IN CHINA
• ZHUO Ga;XIE Jin-nan;MA Jing-xian
• 2000 Vol. 19 (2): 260-264. 
• Abstract ( ) PDF (188KB) ( )
• Statistical relation between typhoon activity and precipitation in China was analyzed with the precipitation at 160 stations and the number of typhoon activity from 1951 to 1996.Results show that remarkable relation exists between the typhoon activity and the annual precipitation on the eastern edge of Qinghai-Xizang Plateau.