Current Issue

• Oscillation Characteristics of Sensible Heat in North Africa and Qinghai-Xizang Plateau and Their Impacts on the Rainfall in East China
• NING Liang;QIAN Yong-fu
• 2006 Vol. 25 (3): 357-365. 
• Abstract ( ) PDF (1036KB) ( )
• By use of the NCEP/NCAR 1948-2002 reanalysis monthly data of sensible heat flux density,the monthly rainfall data at 51 stations of East China in 1951-2000 and the EOF analysis,the oscillation characteristics of sensible heat in North Africa and the Qinghai-Xizang Plateau and their relationship with the rainfall at 51 stations in East China are analyzed.Their spatial coupling patterns and time-lag relationships,as well as the impacts of the sensible heat fields on rainfall are also diagnosed by using the SVD technique.The results show that changes of sensible heat fields in North Africa and over the west of Qinghai-Xizang Plateau are in opposite phase,and both have good time persistence.The sensible heat fields have obvious leading impacts on rainfall in the flood seasons of three regions in East China,including the North China,the Yangtze River drainage area and the South China with evident decadal and interdecadal variations.

• Relationship of Zonal Ozone Seasonal Variations and Planetary Wave in the Stratosphere
• ZHENG Bin;CHEN Yue-juan;SHI Chun-hua
• 2006 Vol. 25 (3): 366-374. 
• Abstract ( ) PDF (718KB) ( )
• The HALOE data from 1992 to 2001 are used to analyze the zonal distributions and the seasonal variations of O₃ mixing ratio in the stratosphere at different latitudes,the results indicate that there are obvious differences of zonal distributions of O₃ mixing ratio in the stratosphere between different seasons.In summer of either NH or SH,the zonal distributions of O₃ mixing ratio are rather small in the stratosphere,and there are disturbances at the middle-high latitudes in other seasons,which strengthen along with the latitude increase and are the strongest in winter.The seasonal variations of O₃ zonal disturbance are similar to the strength of planetary wave in the stratosphere.Together with the NCEP/NCAR reanalysis data,it is shown that the clear signals of wave 1 obtained from the O₃ zonal disturbance and the geopotential height disturbance,which are nearly in phase in DJF at the middle-high latitudes.So the O₃ zonal disturbances are resulted from the planetary wave in the stratosphere.At the middle-high latitudes,wave 1 play the most important role in the O₃ zonal disturbances,while at 30°,the relationship between O₃ zonal disturbances and planetary wave is not very close.At low latitude,planetary wave cannot propagate upward to the stratosphere to affect O₃ zonal distributions.The results are due to meridional O₃ transportation by disturbance flows and influence of basic flow makes observed O₃ disturbance having different phases with the origin disturbance.

• Climatic Features of Boundary Belt for East Asian Summer Monsoon
• TANG Xu;QIAN Wei-hong;LIANG Ping
• 2006 Vol. 25 (3): 375-381. 
• Abstract ( ) PDF (1182KB) ( )
• Using the NCEP/NCAR reanalysis data and observatory station rainfall data in recent 30 years,the climatic features of boundary belt for east Asian summer monsoon and its relation with rainfall of North China and Northwest China are discussed based on rainfall,humidity,wind field,moisture transport,etc.Results show that the boundary belt roughly southwest-northeastly locates along the upper- and middle-reaches of the Yellow River,north part of North China and Northeast China.The summer rainfall along the belt has comparatively large interannual change and the rainfall amount positively correlates with the intensity of summer monsoon.More summer rainfall occurs over Northwest China(north part of North China) when summer monsoon reaches the Northwest China(north part of North China),and vice versa.

• Impact of the Position Abnormalities of East Asian Subtropical Westerly Jet on Summer Precipitation in Middle-Lower Reaches of Yangtze River
• KUANG Xue-yuan;ZHANG Yao-cun
• 2006 Vol. 25 (3): 382-389. 
• Abstract ( ) PDF (658KB) ( )
• An axis index of the East Asian subtropical westerly jet is defined as the mean location(latitude) of the 200 hPa maximum westerly at various longitudes over East Asia using the NCEP/NCAR monthly reanalysis data.The indexcan reasonably reflect the interannual variation of the meridional migration of the East Asian subtropical westerly jet and its impact on the precipitation in the middle-lower reaches of the Yangtze River.Moreover,the index has good correspondence with the East Asia summer monsoon and its interdecadal and interannual changes are consistent with the variations of the rainfall in the middle-lower reaches of the Yangtze River.Comparisons of the circulation differences of the East Asian westerly jet position anomalousyearsshow that when the jet is abnormally northward,the intensity of South Asian high is weaker and the location is far north-westward;and the intensity of the western Pacific subtropical high is weaker and its position is far east-southward in comparison with normal condition.As a result,the anomalous convergence areas of air flows migrate to the regions over the North China,which results in more precipitation there.While the jet is abnormally southward,the South Asia high is too strong and far south-eastward,and the western Pacific subtropical high is stronger and far west-southward,resulting in stronger convergent and ascending flows over the Yangtze River valley,which can easily lead to heavy precipitation and floods.

• Simulation of Impact of the Quasi-Stationary Eddies on Changjiang-Huai River Valley Flooding in Summer of 1998 and 1991
• SONG Min-hong;QIAN Zheng-an;CAI Ying
• 2006 Vol. 25 (3): 390-400. 
• Abstract ( ) PDF (583KB) ( )
• Our earlier investigations show the flooding over Changjiang-Huai River(CHR) in summer of 1998 and 1991 related to the fact that there were more southwest vortexes and long-stayed Meiyu front there,the so-called the transient waves inside the region in the following,and the fact that there were stronger cold air north,stronger Plateau thermal effects west and weaker and far south Subtropical High over West Pacific(SHWP),which is viewed as the external forcing of Quasi-Stationary Waves(QSW) on the large scale outside the CHR.
  To further verify and exhibit the influences of external forcing of QSW on the flooding both in 1998 and 1991,four about 20 day-long-integral simulations with and without the above external forcing of QSW,i.e.,the control and filtered runs respectively,have been run,utilizing the wide-used NCAR MM5V3 model and the NCEP reanalysis gridded data for both the flood cases of July 15~August 5,1998 and July 2~16,1991.Their simulated results averaged over both the whole case processes and each scenario of every 5 days were analysed.Their intercomparisons among the control and filtered runs and the observed illustrated:
  (1) Both the control runs with the QSW forcing can quite well reproduce the observed circulation situation in mid- and high-latitudes,and partly reproduce the observed behaviors of the SHWP and main rain belt;while both the filtered ones,in which the QSW anomalies were removed,produce the circulation and precipitation closer to the normal climate values.Namely,the external QSW anomalies,like the cold air north,plateau thermal effect west and the SHWP south,have the significant impacts on the CHR flooding.
  (2) The PSU/NCAR MM5V3 meso-scale model has the quite good simulative performance in reproducing the circulation in mid- and high-latitudes,especially in the first five days,but the simulated SHWP position and main rainy belt is something north than the observed.Possibly,it relates to the too weak,cold air invading simulated.
  (3) The study implements and tests the regional climatological simulation approach,it can show clearly the effects of QSW anomalies on the regional climate of the simulated domain.

• Influence of the Topography on Lee Wave Amplitude in Three-Layer Modle
• ZANG Zeng-liang;ZHANG Mei;ZHANG Ming
• 2006 Vol. 25 (3): 401-405. 
• Abstract ( ) PDF (316KB) ( )
• A bell-shaped mountain was used to study the influence of the topographic parameters on the amplitude of the lee wave.The theoretical analysis showed that,if the topographic height remains constant,the lee-wave amplitude attains its greatest value when the topographic half-width is suitably the reciprocalof the wave frequency.If the topographic height and half-width vary by different proportions,the variety of wave amplitude is uncertain.Especially,if the topographic height and half-width vary by the same proportion,i.e.the topographic preserves its shape,the maximum amplitude occurs when the half-width is the double reciprocal of the wave frequency.Then,the sensitivity tests were performed to examine the change of topographic parameters by the ARPS model,which are consistent with theoretical results.

• The Effect of Terrain Fluctuation on the Computed Surface Long-Wave Radiation in the Models
• CHEN Bin;ZHANG Yao-cun;DING Yu-guo
• 2006 Vol. 25 (3): 406-412. 
• Abstract ( ) PDF (1010KB) ( )
• The effect of orographic fluctuation(including height and slope) on the calculation of surface long-wave radiation in numerical modelsis elementarily explored in this paper.The results show that the effect of subgrid terrain height change on computed long-wave radiation is not obvious,with a relative error commonly less than 2%.Digital elevation modelwith different resolutions may lead to different slope calculation errors.Slope distributions calculated by using low resolution terrain data have only a little deviationcomparing with that in the high resolution data,but the slope calculation has larger difference in magnitude.The higher the terrain resolution is,the less the error of the real calculation is.While case calculation using high resolution terrain data shows that the regional relative radiation error caused by terrain slope can reach up to above 10%.Thus,in the surface long-wave radiation calculation of numerical model,the more attention should be paid to the effect of orographic fluctuation on the subgrid scale.

• Blocking High Forming and Collapsing with Wave Packet Propagation
• SONG Yan;MIAO Jin-hai
• 2006 Vol. 25 (3): 413-417. 
• Abstract ( ) PDF (995KB) ( )
• The main feature of wave packet pattern with blocking high forming and persisting is without strong energy center in blocking area.At least there are two directions around blocking area to exist obvious strong centers.Usually,1~3 days before blocking high forming often appears blocking wave packet distribution in wave packet distribution map;1~3 days before blocking high collapsing strong wave packet centers move into blocking area,then the blocking high collapses and disappears.

• A Test of the Soil Heat Flux Calculation in Wudaoliang Area Using Meteorological Elements
• ZHANG Li-jie;JIANG Hao;LI Lei
• 2006 Vol. 25 (3): 418-422. 
• Abstract ( ) PDF (301KB) ( )
• Based on the measured data in Wudaoliang area of Qinghai-Xizang Plateau from 1994 to 1997,the variation characters of soil heat flux with time are analyzed.By using of the monthly averaged data from 1994 to 1996,the correlations between soil heat flux and three meteorological elements are analyzed respectively,which are total radiation,ground temperature and the difference between the ground temperature and the underground soil temperature at the depths of 80 cm.At the same time,three corresponding regression equations are established.Applying these regression equations,the soil heat fluxes in 1997 are predictedas a test.The result showsthat it's fairly reliableto calculate the soil heat flux at shallow layers using the total radiation data and the data of the difference between the ground temperature and the soil temperature at the depths of 80 cm as far as the monthly averaged data is concerned.

• Numerical Simulation and Analysis on the Cloud Microphysics Fields of "98.5" Heavy Rainfall of South China in Pre-Summer Flood Season
• WEN Li-juan;CHENG Lin-sheng;ZUO Hong-chao;Lü Shi-hua
• 2006 Vol. 25 (3): 423-429. 
• Abstract ( ) PDF (1271KB) ( )
• In order to fully understand the evolution of the microphysics fields of cloud and the reaction between the cloud physics process and the thermodynamics,the simulated results using the mesoscale model MM5 were analyzed detailedly.The simulated results using the mixed ice phase scheme was the best,because the simulated areas and values of this heavy rainfall were the quite close to the observed.There were no snow in the simulated results,and it was due possibly to the particular cloud microphysics field of South China.The simulated precipitationin each hour usualy weaken first and strengthen then,the physics variables of cloud had the same changes.Heat and vapor transported by the south jet stream were the premise of this rainfall,and latent heat made vertical motion stretched higher.

• Simulation of Impact of Steep Terrain on East Side of Qinghai-Xizang Plateau on Mesoscale Vortex and Rain Storm over the Basin
• HE Guang-bi
• 2006 Vol. 25 (3): 430-441. 
• Abstract ( ) PDF (2810KB) ( )
• The MM5 mesoscale model was used to simulate a heavy rain process taking place in north western Sichuan Basin on 8~10 August 2003 and some numerical experiments with different kinds of changed topographies were run.The results of experiment show that the mesoscale vortex is favorable for the transportation of positive vorticity and the maintenance of convergent and ascending motion,as a result,the precipitation maintenance and heavy precipitation occuring;The influence of topography on mesoscale vortex mainly shows that the steep and complex topography is of advantage for the generation of mesoscale vortex.In the control experiments with the real plateau topography,the vortexes are more and active over the Plateau and western Sichuan Basin;when the topography is altered in both height and slope,the numbers of vortexes reduce,the intensity of vortex weakenes,and the sources of vortex and their moving paths shift;when the topography is removed,vortexes are less,moreover,vortexes move faster than usual;if the topography is cut down only in height,vortex activities change little;when only the Plateau exists,vortexes are still active in the Plateau area,but in no-topography area vortexes deceased apparently.The results also reveal that the activity of vortex has something to do with the distribution of rainfall.

• Impact of the Steep Terrain of Eastern Qinghai-Xizang Plateau on the Genesis and Development of Extreme Heavy Rainfall Event
• LI Chuan;CHEN Jing;HE Guang-bi
• 2006 Vol. 25 (3): 442-450. 
• Abstract ( ) PDF (2297KB) ( )
• Using the high resolotion mesoscale model analysis data,the impact of thecomplex me soscale terrain on the east side of the Qinghai-Xizang Plateau to thegenesis and development of the heavy rainfall event was analyzed.The result shows that the dynamic blocking effect of the Qinghai-Xizang Plateau terrain on atmospheric circulation form the moisture transfer channel over the region of heavy rain scenario occurringand a strong vapor convergence center in the northwest Sichuan and the upper reach of Yellow River.The terrain structure on the east side of Qinghai-Xizang Plateau and the accumulation of vaporin Sichuan Basin also form the high energy tongue and energy front in the lower layer and the potential instability energy in the lower troposphereof Sichuan Basin.The steep terrain on the east side of Qinghai-Xizang Plateau strengthens the ascendant motion.The strongest updraft movement occurredin the convergence area of the vertical shear of east and west wind and the steep landform,stimulating the release of theunsteady energy and rapid developmentof the strong convection.The process is also accompaniedby a mesoscale vortex on the east side of the Plateau.The most significant thermal and dynamical features is very different with mold rain with the high-temperature and high-humidity only appearing in the lower troposphereand strong vorticity column only appearing in the lower troposphere.

• Impact of Nested-Grid Skill on a Mesoscale Convective System Rainfall Event
• HOU Rui-qin;CHENG Lin-sheng
• 2006 Vol. 25 (3): 451-463. 
• Abstract ( ) PDF (3383KB) ( )
• The numerical simulation experiments are conducted using the nonhy drostatic mesoscale model MM5 for a heavy rainstorm event along Meiyu front in the Changjiang basin from 12:00 on 22 to 12:00 on 23 July 2002.The impacts of nested-grid skill on rainfall and mesoscale convective systems are discussed.The results show that the rainfall area shrank reasonably and the spurious rainfall centers comparatively reduced so that the rain intensity and distribution were more approaching to the observational one when the CPS was adopted in the D1 and D2 of triple nesting grid domain.Due to the driving of model nonlinear dynamic,thermodynamic,moist physics process,adopting the two-way interaction multiplenesting mesh technique can make D3 resolve the cloud scale information and pass it to the D2,then to D1 throuth D2.And the dynamic and thermodynamic feedback can do reversely.It can improve the prediction of all nesting grid,but there is a little effect to the position,developing and evolvement of the synoptic system in the D1.On the side,Adopting multiple nesting mesh technique can improve horizontal resolutions of the model forecast area,especially the key forecast area,which can also obtain the improved physical fields.The model can describe what is actually happening about the atmosphere by this way.

• Application of the Wet Q Vector Partitioning Method to the Diagnosis of the Heavy Rainstrom
• YANG Xiao-xia;SHEN Tong-li;LIU Huan-zhu;XUE De-qiang;WAN Feng
• 2006 Vol. 25 (3): 464-475. 
• Abstract ( ) PDF (1672KB) ( )
• Using the ageostrophic wet Q vector to analyze diagnosticallytwo rare heavy rainstorms(one in springand the other in autumn) in Shandong,the results show that the strong ageostrophic wet Q vector convergence forces ascending motions and produces storm rainfall,and that the condensation latent heating plays an important role in producing rainstorm.By dividing the ageostrophic wet Q vector into two parts of parallel and perpendicular to isotherms,the results show that there is superposition of meso-scale and large-scale ascending motions in the two heavy rainstorm,especially in the rain storm of spring,the ageostrophic wet Q vector convergence,perpendicular to isotherms,is approachingto the total ageostrophic wet Q vector convergence,which is nearly the same,parallel to isotherms in the autumn,which also has similar distribution and stronger intensity to the total convergence,so that the meso-scale ascending motion is primaryin the spring,while the large-scale ascending motion is dominantand concomitantwith the mesoscale ascending motion in the autumn,with mainly mixed types of precipitation.

• Mesoscale Numerical Simulation of a Heavy Snowfall Process in Northern China
• JIANG Xue-gong;LI Zhang-jun;KANG Ling;SHI Shao-hong
• 2006 Vol. 25 (3): 476-484. 
• Abstract ( ) PDF (1555KB) ( )
• Using the mesoscale modle MM5,a snowstorm process in the middle and southern part of Inner Mongolia from 14 to 16 March,2003 is simulated.The results shown that the strength,position and time change of heavy snowfall center are successfully simulated.The main effect system of causing snowstorm process is surface inverse trough and 700 hPa meso-α-scale low vortex,and its impact time is relative to the lasting.The couple of divergence in upper troposphere and convergence in lower troposphere producted the short wave trough in upper level induced the heavy snowfall to occur,but it induced two peak values in the snowfall process.Meanwhile,the forming and strengthening of meso-α-scale low vortex and its fitting collocation with warm and wet jet flows in low level are another factor of heavy snowfall occurring.The Yinshan mountain has a great impact on the strength and position of the snowfall process.It made the snowfall strenthened at the south of mountain and minimized at the north of mountain.The lifting of topographic forcing is direction reason of the heavy snowfall.The impact of the topography on the divergence was complex and in this condition the associationbetween the lower level divergence and the ascending motion became faintness.

• Study on Influence of the Mechanical Forcing of Mesoscale Topography on the Extremely Heavy Rainfall in Southern Shaanxi on 8~9 June 2002
• BI Bao-gui;LIU Yue-wei;LI Ze-chun
• 2006 Vol. 25 (3): 485-494. 
• Abstract ( ) PDF (912KB) ( )
• By analyzing the results of the sensitivity experiments about topography causing extremely heavy rainfall in the southern Shaanxi Province during 8~9 June 2002,it is found that the precipitation increment caused by Daba mountains occurs in the southeastern slop of Qinling mountains and lower reaches of Weihe river,while rainfall reduction by Daba mountains appears in the ridge of Qinling mountains and Hanjiang valley;that the gap between Daba mountains play's an important role in transportation of humid warm air flows causing strong precipitation in the south- and east-slopes of Qinling mountains,that Qinling mountains make precipitation increase in the area of Daba mountains,Hanjiang valley and part of northern Shaanxi Province,and decrease in itself,whose effect on rainfall is realized by secondary vertical circulation caused by topography mechanical and thermal forcing,and that elevation change of Qinling mountains have a reverse correlation with precipitation on the mountains and no remarkable relation with precipitation in Hanjiang vellay.

• The Seasonal Climate Division and Precipitation Trends of China in Recent 41 Years
• QIN Ai-min;QIAN Wei-hong
• 2006 Vol. 25 (3): 495-502. 
• Abstract ( ) PDF (630KB) ( )
• Using the day-to-day precipitationdata at 486 stations of China during 1960-2000 and the differential cluster analysis and analogues analysis,as well as taking account of the seasonal and interannual changes of precipitation,the climate regions are divided according to precipitation in China.The suitable sub-region schemes are seeked for the study of different seasonal precipitation in China using the difference index method of interclass and intraclass average correlation coefficients in the dynamic analysis cluster process.The three sub-regions of precipitation in China are obtained in sub-region schemes of annual precipitation: 11,28 and 54 regions.With the same method,the sub-regions of monthly and seasonal precipitation are obtained too.The following climate characteristics can be drawn out from the above:(1) The number of sub-regionsof summer(and its months) is bigger than that of winter,obviously.The seasonal variation of precipitation can be divided into 20 sub-regions and annual variation can be divided into 40 sub-regions.The numbers of sub-regions in winter summer and half-year are both 25 and the numbers in spring,summer,autumn and winter are 25,30,30,22,respectively,in the twelve months,22,27,30,28,28,38,38,34,33,33,23,23.(2) The11 sub-regions of I level have local characteristics in the annual variation of ratio of precipitation in four seasons.

• Characteristic of Temperature on Lightning Return Stroke in Qinghai Area
• YUAN Ping;OUYANG Yuhua;Lü Shi-hua;QIE Xiu-shu;JIA Xiang-dong;ZHANG Hua-ming
• 2006 Vol. 25 (3): 503-508. 
• Abstract ( ) PDF (265KB) ( )
• Slit-less spectra for first return stroke of lightning between the cloud and ground have been obtained in Qinghai Plateau.According to the relative intensities of lines and transition parameters,the temperatures for individual lightning strokes and at different heights of the same discharge channel have been calculated by using multiple-line method.The result shows that the temperatures in return stroke channel vary from stroke to stroke.In generally,the moreintensive lightning discharge,the higher is the value of channel temperature.On the other hand,for a certain return stroke channel,temperatures at different positions show signs of falling away with increasing height alone the discharge channel.

• A Doppler Radar Dynamical Diagnosis of Heavy Precipitation in North China in Spring
• WANG Li-rong;TANG Da-zhang;HU Zhi-qun;ZHANG Yan-gang
• 2006 Vol. 25 (3): 509-515. 
• Abstract ( ) PDF (445KB) ( )
• Performing Doppler weather radar data mainly,and associating with the weather chart fields of physical variable,a areal heavy precipitation process which occurred in North China in April 25 th,2004 was analyzed.The average divergence and vertical velocity in each altitude layer were calculated according to EVAD method which was modified by Gram-Schmidt arithmetic(MGS),the dynamical mechanism in the precipitation process was analyzed primarily,a very fine coincidence was discovered between the weather chart data and the divergence and vertical velocity which were calculated from radar data.Furthermore,there are quite close relation between the precipitation intensity and the convergence and divergence in layers in the range of radar exploring.This study provided some efficiently information for predicting the generating and disappearing of precipitation and artificial precipitation enhancement.

• Extended-VAP Method for Retrieving Wind Field from Single-Doppler Radar.(Ⅰ): Methods and Contrast Exprement
• ZHOU Zhen-bo;MIN Jin-zhong;PENG Xia-yun
• 2006 Vol. 25 (3): 516-524. 
• Abstract ( ) PDF (1284KB) ( )
• Single-Doppler radar radial velocity fields simulated by ideal uniform and vortex wind field are employed to analyze the capability of VAP moethod.Result shows that VAP mthod has stronger capability for retrieving local uniform wind field than that for vortex wind field,and the main reason is related to the assumption of local uniform wind.Hereby,the extended-VAP method is proposed and verified using simulated data for local variational wind fields that do not satisfy the supposition of VAP method.The results show that the extended-VAP method could obviously improve the retrieval result for local variational wind fields,and the retrieved wind fields are more reasonable both on direction and velocity.It has further proven the retrieval capability of extended-VAP method via the retrieval example and the comparason with the result of dual-Doppler analyses.

• The Preliminary Analysis Spatial Agreement between Two Kinds of Hail Frequencies
• YANG Gui-ming;YANG Xiao-xia;ZONG Zhi-ping;MA Xue-kuan
• 2006 Vol. 25 (3): 525-530. 
• Abstract ( ) PDF (271KB) ( )
• Usually,there are two kinds of hail frequency data: One is in the station(F_s);another,in a area(F_a).Are their climate distribution map the same? to answer the question,the two climate maps of hail frequency were made with F_s and F_a.Some intercomparisons with each other were done.Firstly concavity(R) in hail frequency was introduced in order to watch the agreement in relative distribution of hail frequency(F) in two climate maps(as F is relative large,R<ε;relative less,R>+ε;saddle).Secondly,spatial agreement was also calculated used formula introduced.Results indicated(at least) 84% of grid numbers(distribution of high or low value) is agreement in two climate maps.

• Circulation Background for a Severe Convective Hailstorm Weather Process in Yunnan and Its Dopplar Radar Echo Features
• ZHANG Teng-fei;DUAN Xu;LU Ya-bin;HAI Yun-sha
• 2006 Vol. 25 (3): 531-538. 
• Abstract ( ) PDF (1004KB) ( )
• The intensive observation echo data of the Doppler radar and the physical quatities of the severe convective hailstorm weather on 6 July 2001 are analyzed,the results show that the combinations of upper air divergence and lower air convergence form the strong atmospheric instability,the three meso-β-scale convective systems producted under the advantageous large scale background directly cause severe convective hailstorm process in middle part of Yunman.There are many features of Dopplar Radar echoes,such as rear-flank notch,weak echo region(WER),bow echo,gust front echo,hook echo,echo wall,vault,echo overhang etc,and the strong echo areas are related to the areas of the anti-wind,the large radial velocity and wind convergence in Dopplar radar velocity field.

• SVD Analyses of the Precipitation of Northern Part over the Changjiang-Huaihe River Valley from June to July and the Sea Surface Temperature in the North Pacific Ocean
• CHEN Ke-yi;WANG Qian-qian;MAO Wen-shu;MA hui
• 2006 Vol. 25 (3): 539-544. 
• Abstract ( ) PDF (894KB) ( )
• Using the Rotated Empirical Orthogonal Function(REOF),the whole Changjiang-Huaihe region is divided into the Southern area and Northern area according to the first mode of the standardized precipitation departure.The relationship betweenthe precipitation anomalies of Northern area from June to July and the monthly sea surface temperature anomalies(SSTA) are investigated by means of Singular Value Decomposition(SVD) analysis.The results show that Key region lies in North Pacific ocean which influences the precipitation anomaly of Northern area from June to July and the key period of time is from January to February in the same year.SSTA has the best positive correlation with the precipitation in Changiang-Huaihe,in South China and in Northeast China and negative correlation with the precipitation in North China,in Northwest China,in Southwest China.

• Study on Climatic Change and Anomaly of Low Cloud Amount over Qilian Mountain Area
• CHEN Shao-yong;DONG An-xiang
• 2006 Vol. 25 (3): 545-548. 
• Abstract ( ) PDF (331KB) ( )
• Using the low cloud amount of 34 observational stations over Qilian mountain area from January to December in the period of 1961-2000,the spatial anomaly features and time evolution rule of low amount for 40 years were analyzed with EOF and REOF methods.The results show the first three principal components can reflect the whole anomaly structure of season low cloud amount,namely the consistent type in the whole,"+-+" type of east and west changes,north and south change contrary type.The first three loading vector fields of REOF can represent the three principal amount anomaly areas: Chaidamu basin,Qilian mountain area and Hexi corridor.Its turn in to have the different trends,Chaidamu basin'scloud amount had increased trend in each season,especially the amount of cloud notable increased after 1985.Hexi corridor's cloud amounttrend hadn't obviously changed in spring and summer,but in 1990'sthe amount obviously decreasedin summer.Qilian mountain area's trend didn't obviously change in spring and autumn,but the autumn's amount trend increased in 1990'sand decreased in summer.

• Review of High-Altitude Air Discharges above Thunderstorms
• ZHU Bao-you;TAO Shan-chang;TAN Yong-bo
• 2006 Vol. 25 (3): 549-555. 
• Abstract ( ) PDF (614KB) ( )
• Following the discovery of high-altitude air discharges by accident in 1989,there has been a robust effortof experiment-based and theory-based study of these mysterious phenomenaabove thunder-cloud,which leads to the formation of a new branch field of atmospheric electricity.Over most regions of the world,Transient Luminous Events(TLE) produced by high-altutude discharges were observed to occur from the top of thundercloud(about 20 km heights) to the ionosphere bottom(about 100 km heights),with their lasting time ranging from less than 1 ms to beyond 100 ms.These phenomena have been divided into three groups,named Elves,Red Sprites and Blue Jets,respectively.This brief review will summarizesome advance concerning observations and theoretical study of high-altitude air discharges above thunderstorms.