Current Issue

• OCCLUDED FRONTAL CIRCULATION IN UPPER AND LOWER-LEVEL JETS
• JIANG Hou-shuo;Lü Ke-li
• 2000 Vol. 19 (3): 265-276. 
• Abstract ( ) PDF (476KB) ( )
• The evolution and enhancement of occluded frontal circulation in upper-level westerly jet and lower-level southerly jet are discussed by using a dry primitive equation model.The numerical results show that the upper-level jet intensifies greatly the occluded frontal circulation and vertical velocity in frontal zone,and it is advantageous to propagate vertically internal gravity waves excited in frontal zone.The calculations also show that the effects of lower-level southerly jet on occluded front are much smaller than upper-level jet,and it causes smaller enhancement of upward velocity and smooth frontal circulation.The combination of upper and lower-level jets has more complex influences on occluded frontal circulation.

• THE FEATURES OF LIGHTNING FLASH ACTIVITY IN NORTH OF CHINA
• ZHANG Min-feng;LIU Xin-sheng;GE Zheng-mo
• 2000 Vol. 19 (3): 277-284. 
• Abstract ( ) PDF (311KB) ( )
• Based on the cloud-to-ground lightning flash data obtained by direction finder(DF) in Beijing area and North of China,the lightning spatial distributions and the regularities of all lightning factors are discussed respectively for negative and positive lightning in this paper.The results indicate that there are great difference in seasonal and diurnal variation between two type flashes.This gap maybe caused by the different weather patterns and geography features.It is necessary that we should pay more attention to correlations between theweather factors and the lightning activities in order to obtain the realistic reason which lead difference of lightning distributions in different regions.

• DYNAMIC DIAGNOSES OF THE GENESIS AND DEVELOPMENT FOR THE MESOSCALE SHEAR LINE DURING "96.1" SNOWSTORM.Ⅰ:DIAGNOSES OF VORTICITY AND VORTICITY VARIABILITY
• ZHANG Xiao-ling;CHENG Lin-sheng
• 2000 Vol. 19 (3): 285-294. 
• Abstract ( ) PDF (416KB) ( )
• The structure of the genesis and development of "96.1" plateau snowstorm shear line was diagnosed in kinematics and dynamics using the output data of a mesoscale model(MM4),in which a three-phase cloud explicit precipitation scheme has been introduced.The evolution of vorticity field showed that the genesis and development of the local vorticity center or zone not only was directly related to a snowstorm shear line,also predicted its genesis in advance.The vertical section structures of vorticity,divergence,vertical velocity and equivalent potential temperature showed that the inter-allocation and coupling relationship of kinetic and thermodynamic fields were very favorable to the development of snowstorm shear line and the genesis and persistence of the snowstorm.Diagnoses of the vorticity variability revealed that the positive vorticity variability center originated near the snowstorm shear line,its space-time evolution was basically consistent with that of the positive vorticity which was associated with the genesis and development of shear line.In the factors of contributing to the vorticity variability the relative numeric of nonlinear interaction vorticity variability was the most component;the time-mean vorticity variability was less important;the contribution of the perturbation vorticity variability related with strong disturbed flow was small.In the forcing terms of the total vorticity variability,the divergence term contribute most;less was the horizontal vorticity advection term;the vertical vorticity transport and the twisting term played the opposite role,and roughly offset.

• THE PERIODLY VARIATION OF ANNUAL PRECIPITATION IN EAST GANSU
• LI Dong-liang;XIE Jin-nan;WANG Lei;BAI Hu-zhi;LIU De-xiang
• 2000 Vol. 19 (3): 295-303. 
• Abstract ( ) PDF (326KB) ( )
• Nine stations annual precipitation data of east Gansu have been used by means of harmonic analysis and wavelet analysis.From 2 to N/2 years period were calculated and from 2 to 10 years period were experimented in phase space of 10 years and 20 years time sequence.It is shown that the significance level of quasi-3 years period of annual precipitation is the best in central Gansu.East Gansu has 9 years period,south Gansu has not signal period.The period experiment of phase space shown,the quasi-3 years period of annual precipitation of central Gansu is mainly in from 1950's to 1970's,the quasi-9 years period is signally in last 20 to 30 years.the quasi-2 years period oscillation of East Gansu is the mainly in last 10 years.Make further analysis for quasi-3 years period of annual precipitation of central Gansu at the lower point now in the past records,but it has 19 years and over 28 years long period.Maybe it can be return to the significance level in 2000's.The 9 years period shows 23 years rhythm clearly now,but maybe it go into a relatively weak in the coming.

• EVOLUTION OF MONTHLY EARTHQUAKE AND GROUND TEMPERATURE AND PRECIPITATION FIELD DURING 1996~1998
• LIU Yan-xiang;GUO Wei-dong;TANG Mao-cang;MA Wen-ting
• 2000 Vol. 19 (3): 304-312. 
• Abstract ( ) PDF (356KB) ( )
• The relationship of the geothermal vortex evolution and precipitation are analyzed by the data of monthly ground temperature,earth rotation and earthquake during 1996~1998 over China.The result shows that the vortex is increased and the precipitation is more in a fast month of rotation;Vice versa in slow month.The earthquake is a strong signal on developing of the vortex.

• COMPARISON OF SIMULATED RESULTS OF REGIONAL CLIMATE IN SUMMER OVER QINGHAI-XIZANG PLATEAU AND NORTHWEST CHINA
• LIU Li-ping;QIAN Yong-fu;WU Ai-ming
• 2000 Vol. 19 (3): 313-322. 
• Abstract ( ) PDF (441KB) ( )
• With GCM and regional model nesting into GCM the regional climate in summer in Qinghai-Xizang Plateau and northwest China was simulated,and the simulated results by two models were compared with observed results.The results showed that GCM could only reproduce the largescale climatic properties but failed in simulating the mesoscale systems.The simulated precipitation amount by GCM is reasonable.The regional model nesting into GCM can distinguished some regional climatic features including mesoscale systems in summer over Qinghai-Xizang Plateau.The nesting technique improved the simulation of regional climate in this area.The differences between simulate results by GCM and observed results effects the simulation skill of regional model,especially on the edge of model area.

• ANALYSIS OF THE SURFACE TEMPERATURE OVER QINGHAI-XIZANG PLATEAU FROM SATELLITE
• JIANG Hao;WANG Ke-li
• 2000 Vol. 19 (3): 323-330. 
• Abstract ( ) PDF (317KB) ( )
• Using surface temperature data set of the ISCCP-C2,spatial features and temporal variability of the surface temperature over the Qinghai-Xizang Plateau are discussed through EOF analyses.The impact and response between the thermal state on the surface and climatic variation of precipitation and monsoon are investigated.Representativeness of the meteorological observing station is analyzed and three subregions are compartmentalized for the surface temperature overQinghai-Xizang Plateau.

• ROSSBY WAVE AFFECTED BY LARGE-SCALE TOPOGRAPHY OF QINGHAI-XIZANG PLATEAU
• LIU Shi-kuo;BAI Jing-yu;CHEN Hua
• 2000 Vol. 19 (3): 331-338. 
• Abstract ( ) PDF (287KB) ( )
• On the basis of analysis on dynamic and thermal effects of large-scale topography of Qinghai-Xizang Plateau we will focus to analyze the effect of slope and diabatic heating of Qinghai-Xizang Plateau on the 2-D Rossby wave.It is shown that the effect of topography slope of Qinghai-Xizang Plateau on Rossby wave is equivalent to the effect of Rossby parameter;it is a circle between phase velocity and group velocity( c_gx- c_x) ²+ c_gy ²= R ²;and the heating effect is just equivalent to the effect of horizontal convergence.The slope and biabatic heating will make 2-D Rossby wave turning into low-frequency wave.

• THE CHARACTERISTICS OF ELECTRIC FIELD OF HAILSTORM WEATHER IN NAGQU AREA OF QINGHAI-XIZANG PLATEAU
• ZHOU Yun-jun;CHEN Chen-pin;LIU Li-ping;CHU Rong-zhong;FENG Jin-ming;ZHANG Tong;SONG Xin-min;M. Kajikawa;H. Fujii;Y. Aoi;T. Koike;S. Shimizu;K. Ueno
• 2000 Vol. 19 (3): 339-347. 
• Abstract ( ) PDF (407KB) ( )
• The characteristics of electric field of hailstorm weather in Nagqu area of Qinghai-Xizang Plateau are analyzed.The results show that the lightning is observed in the central and strongest convective cell,all eletrical fields of hailstorm weather are almost minus,the strongest electric fields in all the hailstone weather are stronger than-22 kV·m ^-1 and weaker than-48 kV·m ^-1.In the hailstone weather,with the eletric field getting weaker,the number of all sizes of hailstones is decreasing.The coherence between the electric field and the number of all sizes of hailstones in different diameter scope is very good.In the proceedings of hailstone weather,with the time of hailstone falling getting near,the electric field is getting stronger and stronger at first,and then getting weaker.At same time,with hailstone falling time getting near,the number of the lightning per 5 minutes is increasing,and the peak value almost appear at the hailstone falling time,it appears about 3 minutes later than the hailstone falling time.The average peak value is 43.After the peak value appears,the value begins to decrease,but the decreasing speed is slower than the one of increasing speed.The non-inductive charging mechanism is the major electrification processes in the hailstone weather.So the electric field and the number of lightning per 5 minutes can be used as indicator of hailstone weather.In the proceeding of hail falling,especially in the latter mature stage of hailstorm cloud,hail rate and lightning number appear to be anticorrelated.

• CLIMATOLOGICAL RESEARCH OF LIGHTNING IN XICHANG LAUNCHING SITE AND SOUTHWEST OF SICHUAN DISTRICT
• JIANG Xiao-hua;LAI Shun-lai;LI Jian-yun;ZHANG Dong-chun;WANG Li-hua
• 2000 Vol. 19 (3): 348-362. 
• Abstract ( ) PDF (527KB) ( )
• During 1994 to 1998 the lightning sounding data of Xichang launching site and southwest of Sichuan district are analyzed in detail.The climatological probabilities of strength and stroke number are given respectively for cloud-to-ground lightning.The climatological laws of the diurnal circle and yearly variation and the special distribution are also given respectively for lightning in this paper.The climatological characteristics of the lightning in Xichang launching site and southwest of Sichuan district are compared with Beijing-Tianjin-Hebi district.The results show that the climatological characteristics of lightning could exhibit the climatological regularity of the connective activity on time-space distribution.

• A STUDY ON CHARACTERISTICS OF CHANGE OF MAXIMUM MIXING DEPTHS IN LANZHOU
• WANG Shi-gong;JIANG Da-bang;YANG De-bao;SHANG Ke-zheng;QI Bin
• 2000 Vol. 19 (3): 363-370. 
• Abstract ( ) PDF (294KB) ( )
• According to the fundamentals of estimating maximum mixing depths(MMD's) by the assumption of a dry adiabatic lapse rate,two methods of calculating MMD's,that is,a method of solving dual linear equation groups and a method of stepwise approach,have been presented.By using the latter and the everyday meteorological data f rom Meteorological Observing Station of Lanzhou during 1988~1992,the MMD's in Lanzhou Proper were calculated and their variable characteristics with time were analysed.The results were as follows:Annual variation of monthly mean MMD's accorded with a single cycle pattern,that is,the minimum value(716 m) of monthly mean MMD's occurred in December but the maximum value(2 074 m) of them occurred in May.An annual variable tendency of ten-day meanMMD's almost corresponded with that of monthly mean MMD's except two peak values occurring in the last ten days of April and June respectively.In addition,the MMD's in Lanzhou Proper varied with different synoptic systems.The mean MMD was minimum(735 m) before cold-front passage.But it was maximum(946 m) when Lanzhou Proper was controlled by the front of a high pressure system after cold-front passage.Annual variations of monthly mean concentrations of SO ₂,CO and NO _X were also single cycle pattern separately.But their phases were almost contrary to that of annual variation curve of monthly mean MMD's,that is,the three air pollutants were all corresponding to the minimum value of monthly mean MMD's in December.The correlation coefficents between the ten-day mean concentrations of SO ₂,CO,NO _X and the monthly mean MMD's were-0.774,-0.827 and-0.743,respectively.These showed that their negative correlations were remarkable.In other words,the MMD's were a primary factor affecting air pollution in Lanzhou Proper.

• STATISTICS ANALYSIS OF CHARACTERISTICS OF CONTINUING CURRENT IN C-G LIGHTNING
• ZHANG Cui-hua;ZHANG Yi-jun;ZHANG Guang-shu;WANG Cai-wei
• 2000 Vol. 19 (3): 371-378. 
• Abstract ( ) PDF (287KB) ( )
• The electric field change measurements with high time resolution in Gansu and Guangdong areas were analyzed statistically.The characteristics of continuing current in C-G Lightning were discussed.The results indicate that of 103 C-G lightning flashes in Gansu,49.5 percent of lightning contain continuing current.The mean duration of the continuing current is 88.9 ms.While of 98 C-G lightning flashes in Guangdong,52 percent of lightning contain continuing current.The mean duration of the continuing current is 158.2ms.The most of containing continuing current lightning have 2~3 return strokes.There is an inverse relation between the duration of the interstroke interval just preceding the interval containing continuing current and the duration of the continuing current.

• THE TEST STUDIES ON THE MEAN GENERATING FUNCTION FIELD MODEL OF PRECIPITATION FORECAST
• ZHANG Wan-cheng;XIE Ming-en;ZHANG Rong-hua
• 2000 Vol. 19 (3): 379-384. 
• Abstract ( ) PDF (232KB) ( )
• Based on mean generating function principle,the predict and field are analysed by Empirical Orthogonal Function(EOF) method,time coefficient is given to be accepted as predictor and predictive model is set up using stepwise sieving to choose predictors.The mean generating function field model is applied to the precipitation prediction in rainy season and rainfall in May of Yunnan province.The predictive result shows the model has a certain virtue in the forecasting of regional rain and multi-step prediction capacity.

• OBSERVATION AND ANALYSIS OF WATER DYNAMICS FOR SOIL AND SPRING WHEAT IN HEIHE AREAS
• XIE Zhong-kui;WANG Ya-jun;LAN Nian-jun;QI Xu-sheng
• 2000 Vol. 19 (3): 385-390. 
• Abstract ( ) PDF (232KB) ( )
• The laws of soil moisture variations on the state of evapotranspiration in Heihe areas has studied.It has made observations and analyses on diurnal variations of the water potential,stomatal resistance and transpiration rate of spring wheat under various soil moisture conditions and different leaf-positions.Comparison of the water potentials of leaf,sheath and culm has done.The relationships of soil moisture with leaf water potential and stomatal resistance as well as the effects of soil moisture on them have also been analyzed and the relationships have been expressed by empirical equations.

• ON THE OPERATIONAL APPLICATION OF REAL-TIME SHORT-RANGE FORECAST OF SEVERE CONVECTION
• HU Fu-quan;GUO Min;ZHANG Jia-cheng
• 2000 Vol. 19 (3): 391-396. 
• Abstract ( ) PDF (220KB) ( )
• θ _se characteristic method is a short-range forecast of severe convective weather.It can make severe convective weather forecast into predicting presaging severe convective high probability events under trigger mechanism condition.From 1995 to 1998,the accuracy of real-time short-range forecast in Shanghai area has reached 89 percents.

• PRECEDING ATMOSPHERIC CIRCULATION FEATURES OF SPRING LOWER TEMPERATURE OF YUNNAN
• ZHAO Hong-xu;XIAO Zi-niu;HE Hua
• 2000 Vol. 19 (3): 397-400. 
• Abstract ( ) PDF (166KB) ( )
• Spring lower temperature of Yunnan is defined as cold and frost of late spring that occurs often from February to April.Studies show that activities of 10~20 days oscillation during microtherm are protruding and circulation features in preeceding winter differ from normal years.Also using zonal gradient of geopotential height is better than height for temperature forecasting and analyzing.