Current Issue

• THE DIAGNOSIS OF SYMMETRIC INSTABILITY OF THE "93.5" BLACK STORM
• WANG Wen;CHENG Lin-sheng
• 1999 Vol. 18 (2): 127-137. 
• Abstract ( ) PDF (442KB) ( )
• With the criteria of linear and non-linear symmetric instability,the mechanism of a black storm occurred in the Northwest China from 4 to 6 May 1993("93.5") is diagnosed by using three time level output data of a MM4 model which well simulated the developing structure and evolution of the "93.5" black storm.The results show that the location of maximum of the wet bulb potential vorticity is corresponding to that of squall line and from the vertical cross section chart of pseudo angular momentum and potential equivalent temperature ( M- θ _e) it can be seen that the region where the slope of θ _e surface is more vertical than the M is also consistant to the movement of the black storm.The linear conditional symmetric instability is a possible explanation for the squall line.The Lagrangian parcel theory is applied to diagnose the "93.5" black storm and it is shown that the positive σ ² or negative fq (∂lnθ/∂ z) ^-1 and the cusp catastrophe are corresponding to the developement and movement of the squall line,limited comparison lends some support to the hypothesis that non-linear CSI can be a dominant formative mechanism of the black storm,though more sophisticated studies are required.

• THE RESEARCH OF SEVERAL ASPECTS OF FOUR-DIMENSIONAL VARIATIONAL DATA ASSIMILATION
• FENG Wu-hu;QIU Chong-jian
• 1999 Vol. 18 (2): 138-146. 
• Abstract ( ) PDF (339KB) ( )
• It is possible that both observational data error and model error will influence results through four-dimensional variational data assimilation.According to this,some numerical experiments are performed on a shallow water equation model.In these experiments initial data and model error parameter are adjusted simultaneously or sequentially as control variables.It shows when taking initial data as control variables,model error will be aliased to the initial fields if model equations exist error.Although it can be well adjusted during the periods of assimilation,it may not have good forecast after assimilation.But if taking model error parameter as control variables,although model error will varies with time,we can substitute it with constant model error control if the errors in the model have small effect,otherwise,assimilation will fail.It shows when initial data and model correction term adjusted simultaneous as the control variables,perhaps it will be the best,but the choice of scale will influence the results

• STUDY ON RELATION BETWEEN ABNORMAL SNOW COVER OVER QINGHAI-XIZANG PLATEAU AND ENSO CYCLE
• CHEN Qian-jin;GAO Bo;SUN An-jian
• 1999 Vol. 18 (2): 147-161. 
• Abstract ( ) PDF (758KB) ( )
• Firstly,based on the observatory data and composite analyses,the characteristics of two abnormal processes of yearly change of snow cover in winters over Qinghai-Xizang Plateau in 1980'have been studied,and the relationship between the snow cover anomaly and ENSO cycle have been analyzed.The results show that the mean 500 hPa geopotential height field exhibited obviously different wave pattern when the snow cover in winter over Qinghai-Xizang Plateau was more or less than normal.The atmospheric circulation was characterized by weakened/enhanced East Asian Trough,and far east/far west of East Asian Trough when Qinghai-Xizang Plateau got more/less snow in winter,resulting in warmer/colder winter in China.Consistenting with these,the tropical atmosphere circulation and SSTA also showed reverse patterns.The strength of cumulus convection over southern part of South China Sea is pronouncedly different,and sea-air interaction over India ocean and Pacific ocean tended distinctly to evolution of El Ni no or La Ni na.Finally,the local Hadley circulation as a connector played an important role in the interaction between midlatitudes and tropical atmosphere circulation

• THE RELATIONSHIP BETWEEN THERMAL REGIME IN QINGHAI-XIZANG PLATEAU AND PRECIPITATION IN SICHUAN BASIN DURING FLOOD SEASON
• YE Yue-Zhen;FANG Zhi-Fang
• 1999 Vol. 18 (2): 162-170. 
• Abstract ( ) PDF (347KB) ( )
• Based on the data set of the perpetual snow duration and temperature in the Plateau and precipitation in Sichaun Basin.The relationship between the thermal regime distribution in the Qinghai-Xizang Plateau and the precipitation in the Sichuan Basin during the flood season was investigated using the Singular Value Decomposition method.The results are as follows:the distribution character of the Plateau perpetual snow duration is that the centers are located in the Bayanhar mountain and Nyainqêtanglha mountain.The anomaly in these area in winter related to the precipitation in the middle part of Sichuan Basin during flood season.There is close relationship between the large extent anomalies of the temperature in Qaidam Basin and Qilian mountain and the flooding in the west part and the drought in the east part of Sichuan Basin.The prepetual snow duration and the temperature in the Plateau should be consider as the factor of the long forecasting for the precipitation in Sichuan.In general,the period for prepetual snow bring atmospheric circulation and precipitation into effect is longer than the temperature,because of snow melting and water into the soil need long time.The August precipitation in Sichuan Basin obviously are affeced by the snow and temperature in the Qinghai-Xizang Plateau.

• A NUMERICAL EXPERIMENT ON "93.8" HEAVY RAIN OF THE SOUTHWEST OF SHANGDONG
• ZHOU Zu-gang;ZHANG Wei-huan;CHENG Xin-xi;FAN Hong-jun
• 1999 Vol. 18 (2): 171-178. 
• Abstract ( ) PDF (318KB) ( )
• In order to research the important influence of the meso-scale topography on Chinese weather,an improvement has been made on the horizontal and vertical resolution of REM,and the heavy rain case of August 4 to 5,1993(called "93.8") has simulated with the higher resolution model.Using the routine data to get initial field and model topography by envelope method.Compared to the forecast results of model A,B and C,observation,it is found that the precipitation and circulation pattern forecast of model C has been improved greatly than that of model A and B.It is found that meso-scale topography has an important influence on heavy rain forecast.

• INTERDECADAL FLUCTUATION OF ASIAN SUMMER MONSOON AND THEIR RELATION TO ASTRONOMICAL FACTORS
• WEI Jie;TANG Mao-cang;FENG Song;ZHANG Li
• 1999 Vol. 18 (2): 179-184. 
• Abstract ( ) PDF (227KB) ( )
• On the basis of the moving t-test method and correlation analysis,the relation among summer monsoon in South Asia,East Asia and Tibet and their relationship with astronomical factors (sunspot cycle length and earth rotation velocity) were analyzed.The results show that the three kinds of Asian summer monsoons have close relation at interdecadal scale,though they have no appreciable relation at interannual time scale.Moreover,the interdecadal fluctuations of Asian summer monsoon have good relation with the astronomical factors,especially the earth rotation velocity. The physical link between astronomical factors and Asian summer monsoon were discussed.

• OLR FIELD CLIMATIC FEATURES OVER YUNNAN AND AROUND AREAS
• XIE Ming-en;LU Ya-bin;PU Gui-ming
• 1999 Vol. 18 (2): 185-191. 
• Abstract ( ) PDF (269KB) ( )
• Using NOAA's monthly mean grided Outgoing Longwave Radiation (OLR) data with the grid of 2.5°×2.5°Lat/lon during the past 15 years,the radiation climatic feature over Yunnan and around areas have been analysed.The result shows OLR distribution is longitudinal pattern ,it is low in north region and high in south region during winter monsoon,it is reversed during summer monsoon.OLR mean values over Yunnan is greater than the Qinghai-Xizang Plateau and less than South and Southeast Asia tropical regions.The variation of OLR over Yunnan and the Qinghai-Xizang Plateau is reversed in monthly time phase,but Yunnan is similar to India,Bay of Bengal,Indochina Peninsula and South China Sea in OLR monthly curve features.The annual range of OLR over Yunnan is the least.The OLR curve over Yunnan has better negative relationship with precipitation,the yearly mean correlation coefficient is-0.59.

• CANONICAL CORRELATION ANALYSIS TO THE TEMPERATURE FIELDS BETWEEN AUGUST AND SPRING IN YUNNAN
• DUAN Xu;YAN Hua-sheng;DONG Xie-qiong
• 1999 Vol. 18 (2): 192-198. 
• Abstract ( ) PDF (256KB) ( )
• The temperature fields between August and spring of Yunnan were studied by using canonical correlation theory.It is found that the temperature fields in August of Yunnan and southern branch westerly trough,subtropical high,Kunming quasi-stationary front are related to the strength variation of them.The microthermal climate in August of Northwest Yunnan is positive correlation to the strength variation of southern branch westerly trough in February and subtropical high in March and Kunming quasi-stationary front in April.

• SIMPLE INTRODUCTION OF THE NCEP/NCAR 40 YEARS GLOBAL REANALYSIS DATA AND THEIR DECODER/DISPLAY SOFTWARES
• SU Zhi-xia;Lü Shi-hua;LUO Si-wei
• 1999 Vol. 18 (2): 199-208. 
• Abstract ( ) PDF (354KB) ( )
• The NCEP/NCAR 40 years global reanalysis data have been introduced,which are the best at present and have the longest data sequence (1957~1996),the very abundant observations and the same analysis scheme have been used in whole analysis process.The outputs include four categories.Observational archive,synoptic archive, "time series" archive,Quick-look CDROM and a special CD-ROM.The output variables are classified into four classes (A,B,C and D) depending on the degree to which they are influenced by the observations and the model.There are 4-times/2-times every day,daily/monthly mean basic variables and 2(or 3)-dimension diagnostic fields on each standard pressure level,isentropic surface and sigma level.They are useful for the numeral simulation and the weather,climate diagnostic analysis.

• THE EXAMINATIONS AND ANALYSIS OF NCEP/NCAR 40 YEARS GLOBAL REANALYSIS DATA IN CHINA
• SU Zhi-xia;Lü Shi-hua;LUO Si-wei
• 1999 Vol. 18 (2): 209-218. 
• Abstract ( ) PDF (443KB) ( )
• The confidence of the NCEP/NCAR 40 years reanalysis data in China have been preliminarily examined for temperature,pressure,wind,moisture,precipitation,surface radiation,surface sensible heat,surface latent heat and surface heat source (sink) of Qinghai-Xizang Plateau etc. Except the reanalysis precipitation compared with the climatic data for same period,the other variables are not examined by the data of the same periods. The results show that the basic features and distribution patterns of the reanalysis data are almost consistent with the climate data and the reanalysis data are more reasonable.

• THE INFLUENCE OF MOISTURE ADVECTION CALCULATION ON HEAVY RAIN SIMULATION AND A CASE ANALYSIS
• HAN Mei;GE Xiao-zhen
• 1999 Vol. 18 (2): 219-229. 
• Abstract ( ) PDF (435KB) ( )
• A mesoscale model MM4 with improved moisture advection schemes is used to simulate a case of Jiang Huai heavy rain.Through contrasting the simulated moisture field of different moisture advection schemes,and analyzing the dynamical and thermal causes,the reason for different rainfall,includes meso-αand meso-β scale,with different moisture advection schemes,is presented. The results indicate:high accurate and positive definite moisture advection scheme contributes to improve the simulation ability of MM4.

• PRELIMINARY ANALYSIS ON MAXIMUM AND MINIMUM TEMPERATURE CHANGE IN QINGHAI PLATEAU DURING RECENT 40 YEARS
• TANG Hong-yu;LI Xi-fu
• 1999 Vol. 18 (2): 230-235. 
• Abstract ( ) PDF (246KB) ( )
• The linear trends of maximum and minimum temperature in the Qinghai Plateau and their relationship between the both and total cloud amount and sunshine time have been preliminarily analyzed.The results show that the maximum temperatures in the Qinghai Plateau display a weak warming trend in winter and autumn during recent 40 years (1959~1996),but they have obvious cooling trends in spring.The minimum temperatures show warming trend in all seasons especially in winter and autumn.Moreover,the long-term trends of monthly maximum,minimum and average temperatures at the higher altitude areas (higher than 3 000 m) are all weaker than those in the lower altitude areas (lower than 3 000 m).A close relationship between maximum temperatures and sunshine duration and total cloudness exists,while the minimum temperatures show strong relation to total cloud amounts,suggesting that the extreme temperature in this area is influenced by increases of cloud amount and reduced insolation.

• THE RELATIONSHIP BETWEEN THE VARIATION OF HAIL CLOUD SYSTEM AND ITS CLOUD TO GROUND LIGHTNING IN THE EAST PART OF GANSU PROVINCE
• ZHOU Yun-jun;ZHANG Yi-jun;QIE Xiu-shu;GE Zhen-mo;WANG Zhi-jun;WANG Huai-bin
• 1999 Vol. 18 (2): 236-244. 
• Abstract ( ) PDF (329KB) ( )
• Based on the data of the lightning location system and the dual linear polarization radar in east part of Gansu province,the relationships between the cloud to ground lightning and the variation of the hail cloud system are analyzed.The results show that the number of the cloud to ground lightning per five minutes increase suddenly at 30 minutes before the hailstones fall,its average value is about 3.5 at 18 minutes before the hailstones fall,it is not the biggest one when the falling of the hailstones takes place,it always appear between 6 and 16 minutes before the falling,and the negative one is much bigger than the positive one.In three stages of the variation of the hail cloud,the ice phase particles in the center of the hail cloud increase in the beginning,then decrease,just like the number of the cloud to ground lightning;The non-inductive charging mechanism change from strong to weak one.

• THE AREA DISTRIBUTION AND SEASONAL VARIATION OF NDVI OVER HEIFE AREA
• JIA Li;WANG Jie-min
• 1999 Vol. 18 (2): 245-249. 
• Abstract ( ) PDF (356KB) ( )
• Normalized difference vegetation index (NDVI) over HEIFE area in summer and near-winter are derived from Landsat TM data.The spatial distribution and seasonal change of NDVI are obvious due to the complicity of underlying surface in this area.It is shown that the situation of vegetation of surface can be reflected well by NDVI.

• AN IMPROVED SCHEME OF CALCULATING VORTICITY AND DIVERGENCE BY USING TRIANGLE METHOD
• SHANG Ke-zheng;WANG Shi-gong;YANG De-bao;SUN Li-hui
• 1999 Vol. 18 (2): 250-254. 
• Abstract ( ) PDF (236KB) ( )
• According to the definition of vorticity and divergence,an improved scheme of calculating vorticity and divergence has been derived from the triangle method.Compared with the past triangle method,this scheme has more convenient and highter precision of calculation.