Current Issue

• Impact of Pressure System Anomaly over Mid-High Latitude on the Interdecadal Change of East Asia Summer Monsoon
• LIU Yan-xiang;GUO Yu-fu
• 2005 Vol. 24 (2): 129-136. 
• Abstract ( ) PDF (321KB) ( )
• The interdecadal changes of both the East Asia summer monsoon(EASM) and the pressure system anomalies over China-Mongolia areas(30°~55°N, 70°~120°E) as well as their relationship have been analysed, utilizing NCEP/NCAR reanalysed gridded data from 1958 to 2000, the result show that, in the lower and middle layers of troposphere, from the surface to 500 hPa or more, the negative correlation between EASM and the pressure system anomalies is quite clear. The coefficients are -0.67 (for sea level pressure) and -0.69 (for geopotential height on 500 hPa) respectively, which is significant at 99.9% confidence level. A clear change appears in the late of 1970's. In the period of 1960-1976, both the surface and 500 hPa, the pressure system anomalies were negative centre over the China-Mongolia areas. It indicates that the areas dominate low pressure trough or cyclone activities. The strong southerly wind enhances the EASM and result in wet summer in North China. However, in the period of 1977-2000, in the China-Mongolia areas dominate the high pressure ridge or anticyclone activities, the stronger northerly wind over North China preveates the EASM flow form moving northward, and causes the weak EASM and the dry North China. Interestingly, on 100 hPa, mean geopotential height anomaly appears a dipole pattern: During the period of 1960-1976 it was higher in the east, lower in the west; vise versa during the period of 1977-2000. It would be needed further to study.

• Parameterization of Subgrid Topographic Slope and Orientation in Numerical Model and Its Effect on Regional Climate Simulation
• ZHU Xin-sheng;ZHANG Yao-cun
• 2005 Vol. 24 (2): 137-142. 
• Abstract ( ) PDF (1372KB) ( )
• It is a very important and difficult problem to deal with complex terrain effectively in numerical weather forecast and climate models. A parameterization scheme of subgrid topographic slope and orientation in a p-σ regional climate model developed in Nanjing University has been proposed to improve the calculation of surface energy balance in the regional climate model over complex terrain areas. Numerical experiment results by using p-σ regional climate model show that the parameterization scheme of subgrid topographic slope and orientation can improve the simulation of 500 hPa geopotential height and especially the summer rainfall over East Asia.

• Analysis and Description of West Pacific Subtropical High Using TBB Data
• YAO Xiu-ping;LIU Huan-zhu;ZHAO Sheng-rong
• 2005 Vol. 24 (2): 143-151. 
• Abstract ( ) PDF (4992KB) ( )
• The distribution and evolution of TBB and the u=0 contour at 500 hPa in West Pacific Subtropical Region(WPSR) is analyzed in this paper. The results showed that the belt of TBB≥275K in the WPSR, which corresponds with that of West Pacific Subtropical High(WPSH), shifts northward first and southward later with the season's change, therefore the region of TBB≥275K can be used to describe the zone of WPSH and the corresponding TBB's scale described by WPSH changes with seasons; the ridge line of WPSH (the u=0 contour at the level 500 hPa) also agrees with the axis of the zone of TBB≥275K. Meanwhile, it can be revealed that WPSH described by TBB matches better to the heavy rain region than 588 gpdm contour, avoiding from the false defect in drawing WPSH by 588 gpdm contour. Moreover, TBB data set of every 3 h is beneficial to the heavy rain forecast.

• Climatic Characteristics of Monthly Mean Height Field on 30 hPa in Stratosphere
• YANG Jing;QIAN Yong-fu
• 2005 Vol. 24 (2): 152-159. 
• Abstract ( ) PDF (2589KB) ( )
• Using the monthly mean height and wind fields on 30 hPa of NCEP/NCAR reanalysis data from 1958 to 1997, the climatic characteristics in the stratosphere of Northern Hemisphere have been analyzed. The features of the various eigenvectors of the EOF and their corresponding time coefficients are discussed.It is found that the first EOF mode of height field has in-phase and evident variations. In the stratosphere of Northern Hemisphere, there is a circumpolar cold low in winter, and for a circumpolar warm high in summer. Taking January and July as the representations of winter and summer, the characteristics of different spatial oscillation patterns in winter and summer are analyzed by using EOF, and the periods of interannual and interdecadal changes are analyzed by using wavelet transfer. The oscillation indexes of the spatial patterns are defined and the climatic change in stratosphere is discussed.

• Numerical Simulation of A Winter Case Low-Level Wind, Temperature and Humidity Fields in Zhungaer Basin
• AO Yin-huan;CHEN Yu-chun;Lü Shi-hua
• 2005 Vol. 24 (2): 160-166. 
• Abstract ( ) PDF (2295KB) ( )
• The local climatic effect of Zhungaer basin, Xingjiang in winter was simulated through the MM5V3 meso-scale model and NCEP reanalysed data. The simulations reappear the some typical characteristics in Zhungaer basin, such as mountain valley wind and cold lake effect in the winter. The simulated results are consistent with theory and observational facts. The main results are as follows: The Zhungaer basin is covered with snow in winter, there is bigger albedo at underlying surface, so mountain valley wind in Zhungaer basin is smaller than Heihe area, Gansu Corridor, but there is stronger "cold lake effect" and inversion. The strongest inversion can reach to 10℃.

• Numerical Study on Characteristic of Vehicle Emission Pollutants in Turbulence Boundary-Layer of City
• Lü Ping;YUAN Jiu-yi;ZHANG Wen-yu
• 2005 Vol. 24 (2): 167-172. 
• Abstract ( ) PDF (272KB) ( )
• A numerical model is developed based on Navier-Stokes and K-E equations, and as well as the method of artificial compression. Then the structure of the flow and the characteristics of vehicle emission pollutants in urbal turbulent boundary layer are studied through the numerical model. The result shows that a vortex can be formed in urban street canyon. The concentration of vehicle emission pollutant are stacked on the leewind side of building and the ground, and its gradient change along vertical direction is higher on the leewind side, and low on the windward side. When the wind speed of both sides of building in street canyon is faster, the intensity of vortex flow field is stronger, the speed of pollutant emission is faster, too. When the inflow wind direction towards the street, The center of the vortex is tilt toward leewind side or higher, the released pollutants from urban street canyons become more diluted.

• Interannual Change of Global Solar Radiation over Wudaoliang Region
• LI Ren;JI Guo-liang;YANG Wen
• 2005 Vol. 24 (2): 173-177. 
• Abstract ( ) PDF (249KB) ( )
• Using the observed data of global solar radiation (GSR) and surface-atmosphere temperature differences (SATD), the regression equations between the GSR flux density and SATD are fitted. Monthly average GSR flux density in another fourteen years was computed by the equation. the interannual changes of the GSR flux are analyzed and it is found that the GSR fluxes exist obvious oscillation periods about 6 to 7 years. And the GSR flux density will increased in the last decade of 20 centuries.

• Impacts of Barotropic and Baroclinic Enstrophy Interaction on Ural Blocking Processes
• HUANG Chang-xing;LI Wei-jing;HE Jin-hai
• 2005 Vol. 24 (2): 178-186. 
• Abstract ( ) PDF (508KB) ( )
• The strengthening and weakening of the barotropic enstrophy are the important characteristics of the blocking process over Ural mountains. The main mechanicm of strengthening barotropic enstrophy is the transformation from baroclinic to barotropic enstrophys. The baroclinic enstrophy comes from the net transport from outside to inside of the blocking area and the net growth of the baroclinic enstrophy. The weakening mechanisms of the barotropic enstrophy are the drag machanism and effect. Therefore, the blocking process is the result of barotropic and baroclinic enstrophy interaction. The transportation of baroclinic vorticity under influence of zonal baroclinic wind has great effect on the maintaining and declining of blocking.And the transportation of baroclinic vorticity with the meridional baroclinic wind is vital in the shaping of blocking.The transportation of barotropic enstrophy under influence of meridional barotropic wind and the transportation of mixing enstrophy under influence of baroclinic wind also have key contribution.

• Spatial and Temporal Variation Characteristics of Arctic Oscillation on 500 hPa in Recent Fifty-One Years
• YAN Hua-sheng;DONG Hui-lin;CHENG Jian-gang;CAO Jie;WANG Qing-chuan
• 2005 Vol. 24 (2): 187-195. 
• Abstract ( ) PDF (420KB) ( )
• The monthly mean normalized data of 500 hPa geopotential height field over Northern Hemisphere in 1951-2001 is used to do the EOF analysis according to the each of 12 month, respectively, and then the power density spectrum is used to study the time coefficient changes of the first eigenvector of EOF. The result show that the Arctic Oscillation is the first character of 500 hPa geopontential field circulation anomaly over Northern Hemisphere in recent fifty-one years, and the variance contribution rate is between 10% and 20%. The center at polar area has a remarkable eccentric construction. The areas of the center extend to high latitude in winter and spring, are larger and that of the center in summer and autumn are smaller to polar contracting. The central area at middle-high latitude is also larger in winter than in summer. The regions of from polar to Greenland, from Southwest Europe to Etesian, from Baikal lake to the Japanese Sea and the Southeastern of North America are the major occurring areas of 500 hPa circulation anomaly over Northern Hemisphere. For positive periods of AO, winter is in 1990's; spring, before the middle of 1970's; summer, in 1960's and 1970's; autumn, in the mid-later period of 1980's to the early 1990's. For negative periods of AO winter are in 1950's; spring, after middle period of 1970's, 1950's and 1990's; autumn, the later half of 1990's. And 1998 is the most notable year of AO.

• Atmospheric Instablity Parameters and Forecasting of Ligthning Activity
• ZHENG Dong;ZHANG Yi-jun;Lü Wei-tao;MENG Qing;HE Ping
• 2005 Vol. 24 (2): 196-203. 
• Abstract ( ) PDF (1333KB) ( )
• By using M-LDARS single-station lightning location system data and sounding data in 182 lightning activity processes and 153 no-lightning activity processes in Beijing, the relation between atmospheric instability parameter and lightning activity is analyzed in this paper. The results indicate that the correlation between the latent-convective instability index, lifted index, convective available potential energy and 700 hPa equivalent potential temperature and lightning activity is good, at the same time, the correlation between middle-level humidity and lightning activity is unobvious. In addition, the probabilityof forecasting the lightning activity when these parameters are colligated and the linear regression relation between lightning frequency and these parameters are analyzed. Then, some diagnosisindexes for lightning forecasting are given. These results can provide the reference for lightning inspection and forecasting in Beijing.

• Total Kinetic Energy Budget of Mesoscale Condition in A Severe Dust Storm Process
• KANG Feng-qin;LI Yao-hui;Lü Shi-hua
• 2005 Vol. 24 (2): 204-211. 
• Abstract ( ) PDF (390KB) ( )
• The total kinetic energy budget is computed by the numerical simulative results of MM5 mesoscale meteorological model for studying the energy source and sink of severe dust storm in Northern China on 7~9 April 2001. The results show that (1) the mesoscale kinetic energy budget is very active. (2) the start up and development of the sandstorm system depends on depleting the local kinetic energy which comes from the high altitude. (3) the wind crosses contour resulting in local energy source throughout all sandstorm is the second important energy sink. (4)the horizontal flux divergenence is the maximum energy sink. (5)the vertical flux divergent is the second energy source. As the system is developing, the center of energy source is moving from high to middle levels until the energy sink occurs at high level at the system's vanishment stage.(6) the friction depletion and sub-grid scale effect are the first energy source at total stage.

• Characteristic of Main Meteorological Element Changes and Cause Analyses during Sand-Dust Storm Process in Mid-and North-Parts of Ningxia
• LI Yan-chun;ZHAO Guang-ping;HU Wen-dong;LI Yan-fang
• 2005 Vol. 24 (2): 212-217. 
• Abstract ( ) PDF (266KB) ( )
• Using the routine meteorological data, the duration, variation and causes of related meteorological elements during sand-dust storm process in mid-and north-parts of Ningxia are statistically analyzed. The resoult show that the wind directions have an important effect on the sand-dust storm weather occurring. The time of occurring sand-dust storm under five wind directions from west to north amount to 70% and over of total one. In the same sand-dust storm process, the duration of sand-dust storm at different stations is close related to the topographic, geomorphic and geographic factors, and next to the maximum wind. The influence of maximum wind in the different sand-dust storm processes at same stations on the duration of sand-dust storm is significant. The more the stations of sand-dust storm occur, the longer duration in the same sand-dust storm process is. The sand of Yanchi station during sand-dust storm not only come from the background source but also the local supply.

• 7 Predicting Rules of Di-qi Map Method For Short-Term Climate Prediction
• TANG Mao-cang;ZHANG Yong-jun;LI Dong-liang
• 2005 Vol. 24 (2): 218-222. 
• Abstract ( ) PDF (236KB) ( )
• Based on the thirty year short-term climate prediction experiences, the 7 rules for rainfall prediction of short-term climate are introduced in this paper. Because the physical foundations of these rules are correction, they play an important role on the short-term rainfall prediction. But in some cases they may be incompatible, some further investigations and improvements are still needed.

• Nonhydrostatic Numerical Simulation and Analyses on the Mesoscale Systems of "98.5" Heavy Rain in the South China Preflood Season
• WEN Li-juan;CHENG Lin-sheng;LONG Xiao
• 2005 Vol. 24 (2): 223-231. 
• Abstract ( ) PDF (420KB) ( )
• In order to study in detail the heavy rain event of South China, the simulation for "98.5" heavy rain using the nonhydrostatic mesoscale numerical model was conducted on the basis of synoptic analysis of heavy rain on 23~24 May 1998 ("98.5"). The comparions between the simulated results and objective analysis have shown that the simulated results reappeared the large- and meso-scale circulations. The mesoscale system producing this heavy rain has the warm and wet core. Divergence on upper levels, convergence on low levels,and ascending motion as well as the cyclonic vorticity column are the dynamic mechanisms causing the heavy rain. The southwest jet over low levels is importantfor this heavy rainfall. The centre of the simulated precipitation is close to that of the observed, but its location is southward and westward, rainfall is light. Their simulated precipitation is smaller than the observed. Rainfall usually occur in favorable terrain in where is the bell-mouthed. Simulated results using differentterrain data of high or low resolutions were similar.

• Synthetic Analyses of An Extreme Heavy Storm Rain on the East Side of Qinghai-Xizang Plateau in Early Summer
• ZHANG Hong;SUN Wei
• 2005 Vol. 24 (2): 232-239. 
• Abstract ( ) PDF (1899KB) ( )
• An extreme heavy storm rain on the east side of Qinghai-Xizang Plateau in early summer of 2002 was analyzed. The result showed that the cause of heavy storm rain was the low trough in Xinjiang combined with the Plateau trough, and lead to the convergence of strong cold air and southwest airflow of warm and moist from Sichuan to Shaanxi on the east side of Qinghai-Xiang Plateau. The strengthening of westerly jet in upper level, forming of blocking high in Eastern China, strengthening and extending northward of the warm and moist southerly airflows in low level provide the advantageous conditions for heavy storm rain. The activity of meso-β-scale convective system before warm area of cold front directly cause local heavy storm rain, mesoscale convergence system in low level is closely related to the activity of meso-β-scale convective cloud cluster, timing and precipitation region of heavy storm rain. The especial structure of vertical distribution of divergence in mesoscale convective system, namely the double structures of convergence-divergence from lower levels of troposphere to upper level, has an important role in forming strong ascending motion and deep convective formation of heavy storm rain.

• Mesoscale Analyses of Heavy Storm Rain in the Central Part of Yunnan on June 17, 2003
• HE Ping;LI Hong-bo;HE De-feng
• 2005 Vol. 24 (2): 240-246. 
• Abstract ( ) PDF (1702KB) ( )
• Base on Shuman-Shapiro mesoscale filter mothed, high pass filter under the background of large-scale circulation and analysis of satellite cloud image and radar echo are used to analyze the heavy storm rain in Chuxiong and Nanhua of central Yunnan on June 17, 2003. Results show that the precipitation process is caused by a moved southeastward and well-developed tropical mesoscale cyclone. The surface cold air intruded into the mesoscale depression and led to the development of convective activity, and the cold air was the reason for the strengthening of the tropical mesoscale cyclone. The tansportation of water vapor coming from Begalese Gulf, South Sea and West Pacific Ocean under large-scale circulation provides the energy for the development and maintenance of the severe convection. The low pressure center of surface mesoscale and the north side of the shear line are indicative to the rainfall area.

• Mesoscale Analyses on A Moist Convective Storm Rain Behind Trough
• LIU Yong;ZHANG Ke-xiang
• 2005 Vol. 24 (2): 247-254. 
• Abstract ( ) PDF (1318KB) ( )
• Mesoscale analyses were carried out for a moist convective storm rain behind trough in Shaanxi Province on August 5, 2002. The primary results are as follows:This heavy storm rain was of long-time duration, wide influence and high density, which reflected the synoptic feature of moist convection storm rain. The southward movement of cold advection behind 500 hPa trough was direct factor of this process; θ_se on 850 hPa, frontal zone in the northern part, and energy zone in the mid- and south- parts supplied the energy and caused strong unstable zone of potential for this process. Typhoon named "kammuri"located in the South China Sea, transformed water moistureto the continent, and provided the ample moisture for this process. Moist in the whole atmospheric layer, moist and cold in the upper, caused the moist convection wind storm; second-circulation formed by coupling of high- middle and low-level jets resulted in successive violent updraft. Evere rainfall weather in the northern part of shannxi was caused by one of the two mesoscale cyclones, and short-term storm rainfall and heavy storm rain in the middle and southern parts were caused by amalgamation of two mesoscale cyclones. Effect of sub-circulation might be main reason of surface mesoscale cyclone. The density of radar echo appeared in pieces for this process varied from 45 to 55 dBz, and its cloud height reached to 12~14 km, the maximum was 16 km.

• Diagnostic Analysis of Heavy Rain Process After A Prolonged Drought
• ZHAO Shi-fa;WANG Jing-hong;YAO Yong-sheng;ZHANG Hou-fa;HU Cheng-ying;ZHAO Xiao-ning;LEI Ya-jing;GUO Yan
• 2005 Vol. 24 (2): 255-260. 
• Abstract ( ) PDF (341KB) ( )
• In this paper, a heavy rain process after a prolonged drought in Shangluo, Shaanxi on 1~3 June, 2000 has been analyzed, utilizing various observed and calculated meteorological data. The results show that the heavy rain process not only related to the circulation on large scale of the weaken East Asia trough and the strengthened and extended westward subtropical high over west Pacific etc, but also related to the local characters like strong lower-level-jet, shear line and straticification unstability. When the heavy rain weather occurred, the heavy rain is located in the area with the high energy tongue in the lower level, the center of vapor convergence, the convergence and ascending center in lower level, and the divergence at the upper level.

• Application of Q-Vector Theory to "02.6" Heavy Storm Rain on the East Side of Qinghai-Xizang Plateau
• WANG Chuan;DU Chuan-li;SHOU Shao-wen
• 2005 Vol. 24 (2): 261-267. 
• Abstract ( ) PDF (352KB) ( )
• By using the routine sounding and surface observation data, the circulation features and physical causes for the heavy storm rain process occurred in Shaanxi on the east side of Qinghai-Xizang Plateau on 8~9 June 2002 were diagnosed and analyzed. Furthermore, based on MM4 model output production, a mesoscale analysis was made according to Q-vector theory. The results show that the distribution of wet Q-vector indicates the direction and intensity of the secondary circulation. The heavy storm rain may occur when the mesoscale circulation enhanced. The partition of wet Q-vector indicates mesoscale feature in the heavy storm rain.

• Analysis on A Mesoscale Convective System in North China Plain
• Lü Sheng-hui;GAO Yan-hong;LIU Wei
• 2005 Vol. 24 (2): 268-274. 
• Abstract ( ) PDF (1252KB) ( )
• Meteorological routine observation data are used to analyze a Mesoscale Convective System (MβCSs) on the Meso-β scale which takes place in the North China Plain on June 1, 2002. The results show that the convective system occurs in the wind shear zone, and it locates on the right-hand side of upper-level jet stream, and which exists in the northeast part of North China Plain, due to the influence of the Northeast Cold Vortex. The collective effect of upper-level positive vorticity advection and low-level negative vorticity advection results in both upper-level convergence and low-level divergence, which tend to maintain the ascending motion of middle troposphere in this region. Low-level moisture flux convergence provide plenty of water vapor. Then decreasing(increasing) the total energy of the upper(low)-level airso that a large amount of unstable energy develops over the North China Plain. This circulation pattern favors convective systems and finally triggers the mesoscale convective system. This paper sheds light on the causes of MβCSs and provides some experiences for forecasting MβCSs in the future.

• Analysis on Eurasian Circulation of Drought and Flood in Summer of Chongqing
• LIU De;LI Yong-hua;GAO Yang-hua;LI Jing;TANG Yun-hui;YE Zhao
• 2005 Vol. 24 (2): 275-279. 
• Abstract ( ) PDF (1431KB) ( )
• The summer precipitation indexes in Chongqing have been calculated. The Eurasian circulation circulation in summer at the same period and winter before it and drought and flood in summer of Chongqing have been analyzed by using the correlation, composite analysis and SVD methods. On the basis of them the circulation indexes in key areas have been defined, and the correlation between the precipitation and the circulation indexes have been discussed, too.

• Recognition Model of Hail Cloud Based on Matter Element and Extension Sets in Low Latitude Plateau and Its Result Verification
• LI Gui-hua;JIN Shao-hua
• 2005 Vol. 24 (2): 280-284. 
• Abstract ( ) PDF (216KB) ( )
• Hail cloud recognition is a pattern recognition problem of multi-parameter. The recognition result of hail cloud based on single parameter is always non-compatible. The basic thinking of matter elements and extension set was used for changing the non-compatible problem into compatible problem. After the contrast between it and Chengdu region hail cloud recognition, according to the low latitude plateau terrain and the climate characteristic, and through the suitable increasing parameter, the recognition model of hail cloud on low latitude plateau is completed. The accuracy of hail cloud recognition by this method is over 86%.

• Development and Use of Virtual Digit Video Integraph
• FANG De-xian;ZHAO Kun;LI Ming;GE Wen-zhong
• 2005 Vol. 24 (2): 285-290. 
• Abstract ( ) PDF (839KB) ( )
• The principle and development of virtual digit video integraph (DVIP) are discussed in detail. The integraph simplify the process of dealing with the reflectivity field of the numerical terminal of the weather radar system. All the numerical calculations are completed by the computer, and DIVP is replaced by the software.