Current Issue

• Numerical Simulation about Impact of Vegetation Cover over Australian Land on Asian-Australian Monsoon (I):Impacts on Regional Climate and Winter Monsoon in Australia
• BAO Yan;Lü Shi-hua;LIU Hai-hui
• 2006 Vol. 25 (5): 763-771. 
• Abstract ( ) PDF (1832KB) ( )
• Influences induced by afforestation and desertification on Australian local climate and large-scale circulation,as well as monsoon rainfall in winter were studied by sensitive experiments of afforestation and desertification using CCM3.Results indicated change of land cover has distinct impact on regional climate.Afforestation in mid-west part of Australian land can result in remarkable decrease of air temperature in east of desertification,however desertification can result in notable increase of air temperature in centre Australian land,the change of which is influenced by surrounding ocean environment.Comparing with regional climate change induced by the decrease of local water vapor content in desertification experiment,more marked influence on regional climate induced by increase of water vapor content in afforestation experiment.The change of rainfall has relation with convection strength and production of deviation circulation.The local thermal and moist status can affect the cross-equator air flow and monsoon rainfall by transportation of general atmospheric circulation along longitude direction.Results also showed that afforestation make cross-equatorial flow stronger and increase the possibility of cold wave from Northern Hemisphere invading inland over Southern Hemisphere,where as desertification will make the cross-equatorial flow weaker in range of 100°~110°E and 120°~130°E in lower troposphere,which will further influence Australian monsoon rainfall in winter.The afforestation resulted in strength of flow along northern inshore of Australian land,and monsoon trough moved to south,as well as the movement of rain-belt,and increase the change of precipitation.while in desertification experiment,the north flow weaker,along with the northern flow,which caused the less water vapor transmitted and less rainfall in monsoon trough.

• Numerical Simulation about Impact of Vegetation Cover over Australian Land on Asian-Australian Monsoon (II): Impact on Summer Monsoon System
• BAO Yan;Lü Shi-hua;LIU Hai-hui
• 2006 Vol. 25 (5): 772-780. 
• Abstract ( ) PDF (1609KB) ( )
• The impacts of afforestation and desertification over Australian land on the cross-equatoral flow and monsoon system in East Asia in summer are researched in this paper.Results indicated Afforestation induced the advancing of Somali cross-equatorial flow,as well as the intensifying of cross-equatorial flows at different times,while the effect was reduced in the case of the flows to the east of 90°E,which origin from Australia high.At the same time,afforestation advanced the establishment of Australia high and Mascarene high as well as the northward jump of subtropical high over West Pacific,while the intensity of the latter was weakened,then southwest flow easily extended in to West Pacific and inland East Asia in consequence.Furthermore,In afforestation experiment,establishment of the cross-equatorial southward flow advanced in time,and the northward extension of the flow was amplified.In desertification experiment,the intensity and extension of the southward flow shrank.The change of Australian landuse will cause the intensity of southwest Asia monsoon to change,while its influence on East Asia monsoon is less notable,and this is relevant to the mechanism that afforestation intensified Somali cross-equatorial flow and put relatively minor influence on the flow to the east of 90°E on the other hand.While desertification weakened the Somali flow.the subtropical high on West Pacific in desertification was comparably intense in both spring and summer,and it baffled the northward blow of cross-equatorial flow.It is also demonstrated that Australian landuse change influences the time when East Asian summer monsoon established as well as the seasonal conversion characteristics,especially for south-west monsoon.

• Synoptic Diagnostic Analysis on a Heavy Rainstorm between Yellow River and Huaihe River in Summer of 2004
• YANG Ke-ming;LIN Jian;KANG Zhi-ming;GUO Wen-hua
• 2006 Vol. 25 (5): 781-791. 
• Abstract ( ) PDF (2773KB) ( )
• Based on the NCEP(1°×1°) 6 h reanalysis data,synoptic diagnostic analysis on an abrupt heavy rainstorm between Yellow River and Huaihe River in the summer of 2004 was studied in terms of newly-introduced physical parameters.Results show that the horizontal kinetic term of frontogenetical function contributes most to the formation of rainfall front.The vertical profile of helicity over rainstorm area shows the opposite pattern,with positive and negative respectively in the low-middle-level and upper-level of troposphere.The local variation term is reverse to the advection term no matter for the apparent heat source(Q₁) and moisture sink(Q₂),the vertical transportation term plays a significant role in atmospheric diabatic heating,of which the center was found in the middle and upper levels of troposphere due to the condensation latent heat associated with the convective precipitation.Maxima of frontgenisis,positive helicity and strong heating area are consistent with heavy rainfall area very well.

• Application of the Helicity in a Heavy Storm Rainfall Process in Spring of Shandong Province
• CHI Zhu-ping;LI Chang-yi;LIU Shi-jun
• 2006 Vol. 25 (5): 792-799. 
• Abstract ( ) PDF (1518KB) ( )
• The heavy storm rainfall process in Shandong Province on 17~18 April 2003 is closely related to the warm shear,the occurring and developing of microscale low vortex on 850 hPa,high temperature and abandant moisture.The microscale limited-area model MM5 is used to simulate the heavy storm rainfall process.On the basis of better accurate simulation and using the fine-mesh data of model output, the helicity during the evolution process of heavy storm rainfall is diagnostically analyzed based on the helicity theory and stability condition.The results show that the hight occurred miximum value centre of positive helicity is related to the intensity and weakness of convective development when the severe convective storm occurs in the unstable atmosphere;the long axis in positive value area of 500 hPa helicity is consistent with the causing severe convective warm area's weak shear and moving towards of radar band echo;the variation of helicity intensity has centain indication to the predictions of severe convective moving and developing,as well as heavy strom rainfall's occurring when the heavy strom rainfall occurs near 850 hPa helicity centre.

• Primary Analyses of Teleconnection Relationship between the Qinghai-Xizang Plateau Air Temperature and the Indian Ocean SST
• ZHANG Ping;GAO Li;MAO Xiao-liang
• 2006 Vol. 25 (5): 800-806. 
• Abstract ( ) PDF (1293KB) ( )
• Using the annually temperature data of 54 observational stations over Qinghai-Xizang Plateau(QXP) in 1960-2000,the spatial distribution and climatic anomaly characteristics of temperature over QXP are investigated.The indian ocean sea surface temperature data at the same period and SVD method are used to study the teleconnection relationship between QXP air temperature and Indian ocean sea surface temperature,and their physical mechanism are primarily discussed.The results show that the temperature is lower in the middle of QXP and its surroundings is highter,the trend of QXP air temperature ascends year by year in recent 41 years.The teleconnection relationship between QXP air temperature abnormality and Indian Ocean SST is significant,which probably have something on correlative wave train forced by Indian Ocean SST through the main coupled relationship model.

• Analysis on Structure of Atmospheric Boundary Layer and Energy Exchange of Surface Layer over Mount Qomolangma Region
• LI Mao-shan;Dai You-xue;MA Yao-ming;ZHONG Lei;Lü Shi-hua
• 2006 Vol. 25 (5): 807-813. 
• Abstract ( ) PDF (687KB) ( )
• The Mt.Qomolangma(Everest),the highest peak of the Plateau,is a representative region of mountains of Himalayas.During the Scientific Expedition to Mt.Qomolangma(Mt.Everest) of Chinese Academy of Sciences in spring of 2005,one radio sonde system and one turbulent measurement system[sonic anemo-thermometer(CSAT3)] were set up in the base camp of Mt.Qomolangma(28.137°N,86.854°E,and 5149 m above m.s.l.).Another turbulent system [sonic anemo-thermometer(CSAT3)] was set up at Quzong Station(28.310°N,86.896°E,and 4475 m above m.s.l.).The turbulent flux measurement was set up at 3 m above the ground at both the Stations.The density of water vapor and concentration of carbon dioxide was obtained by an LI-7500 device at the two stations.The field turbulence data,after removing noise and bad records caused by instrument failures,are given every 30 minutes.
  With the observational radio sonde and turbulent measurement data,the structure of atmospheric boundary layer and the characteristics of energy exchange in the near surface were analyzed over Mt.Qomolangma region.The results showed that:(1) The diurnal variation of boundary layer height is obvious,the structure of boundary layer is affected by glacier wind,and its highest is 3888 m which is observed at 14:00 on 21 May when it blows downward north wind.When blowing downward south wind at low layer,the height is less than 600 m.In daytime there is moisture inversion at low layer over Mt.Qomolangma region.(2) The characteristics of energy exchange in the near surface is different with vary altitude and underlying surface at Qomolangma and Quzong Stations.In daytime the sensible heat flux dominates at Qomolangma site,but the latent heat flux is larger than the sensible heat flux at Quzong station.The change time from positive to negative value of soil heat flux at Qomolangma site is earlier than of at Quzong station.(3) Downward shortwave radiation at Quzong station is smaller than those at Qomolangma station,but upward long wave radiation at Quzong station is significant larger than those at Qomolangma station.Upward shortwave radiation at Qomolangma station is larger resulting from high albedo.Such variation is due to sunrise at Qomolangma station earlier than it at Quzong site,underlay situation is different between two sites,the altitude at Qomolangma site is higher than it at Quzong site,and surface temperature at Quzong site is higher than it Qomolangma site.(4) Because of glacier wind prevailing,the structure of boundary layer becomes more complex in this region.

• Processes of Intraseasonal Evolution of Asian Summer Monsoon Under Climatological Mean Condition
• Lü Jun-mei;TAO Shi-yan;ZHANG Qing-yun;JU Jian-hua
• 2006 Vol. 25 (5): 814-823. 
• Abstract ( ) PDF (2305KB) ( )
• Based on the daily data of outgoing longwave radiation(OLR) from National Oceanic and Atmospheric Administration(NOAA) satellites in 1979-1995,the power spectrum analysis and band-pass filter are implemented to investigate the processes of intraseasonal evolution of the Asian summer monsoon under climatological mean.The intraseasonal evolution of subsystems in Asian monsoon region is divided into eight key stages.At every stage,the temporal and spacial structures of the atmospheric circulation and rainfall are analyzed using the National Centers for Environment Prediction-National Center for Atmospheric research reanalysis and Climate Prediction Center Merged Analysis of Precipitation data in 1979-1999.The physical picture of intraseasonal precipitation change of atmospheric circulation and precipitation over the Asian monsoon region is obtained.The result shows that the variability characteristics of circulation systems of Asian summer monsoon subsystems at different intraseasonal evolution stages can primely describe the intraseasonal evolution processes of the entire Asian summer monsoon system.

• The Numerical Experiments of the Effect of Urban Buildings on Boundary Layer Structure
• CHEN Yan;JIANG Wei-mei
• 2006 Vol. 25 (5): 824-833. 
• Abstract ( ) PDF (1726KB) ( )
• Building's effect is developed in Regional Boundary Layer Model.The simulated results illustrate that it can simulated the effect of buildings on urban air flow field.According to the urban morphology,we design the different building heights and densities.The simulated results show that the buildings can weaken the wind speed in urban area and lead to convergence in lower layer atmosphere.The weaken can reach a peak of 1.6 m/s.The dynamic production of turbulence is strengthened and the turbulence transportation is greater.The presence of building leads to a more instable stratification with a mixing layer.The top of boundary layer can improved.It leads to a weaker energy exchange between atmosphere and the earth.In daytime the heat exchange between atmosphere and the earth is weakened while strengthened at night.All of the simulations illustrate that the buildings play an important role in urban air flow field and boundary layer structure,particularly when wind speed is great.

• Transfer Coefficients of Sensible Heat under the Atmospheric Stability in Near Surface Layer over Dunhuang Gobi
• WEI Zhi-gang;HUANG Rong-hui;CHEN Wen
• 2006 Vol. 25 (5): 834-839. 
• Abstract ( ) PDF (1455KB) ( )
• At first,the transfer coefficients(C_h) of sensible heat from September 1,2000 to September 30,2001 over the Dunhuang Gobi were computed and analyzed by aerodynamic method.The mean C_h is 0.00203±0.00045.In the near-neutral and neutral stratified atmosphere,C_h is constant,C_hn≈0.0020.In the stable atmosphere,C_h is relatively small and increasing with the wind speed and gets bigger and trends to C_hn, C_h=0.0012+0.0003ln(V).In the unstable atmosphere,C_h is relatively large and decreasing with the wind speed and gets bigger and trends to C_hn,C_h=0.0026-0.0002ln(V).Then,the bulk Richardson numbers (R_b),which were used to determine the atmospheric stratified stability,were computed by the surface temperature,the air temperature at only a high and the wind at another high.The C_h is R_b-dependent.

• Characteristics of the Changes in Pan Evaporation over Northern China during the Past 45 Years and the Relations to Environment Factors
• LIU Bo;MA Zhu-guo;Ding Yu-guo
• 2006 Vol. 25 (5): 840-848. 
• Abstract ( ) PDF (1525KB) ( )
• Analyzing the time series of the whole Northern China and the sub-regions of it,Northeastern China,northern China,the east part and the west one of Northwestern China,it is found that the pan evaporation obviously decrease in the past 45 years(1961-2004).And the space pattern of change is: Pan evaporation declined least in the Northeast China,when moving westward,its decrease trend gradually increase.Analysis of the relations among pan evaporation and some environment factors,for instance,wind speed,precipitation,relative humidity and diurnal temperature range,etc,show that either whole North China or in its sub-regions both the diurnal temperature range and wind speed were the most important factors,while precipitation,relative humidity and temperature,etc,were also important impact factors on pan evaporation.In total,many meteorology factors have a close correlation with pan evaporation.The correlation changes with the change of time and space in the past 45 years,the influences of the diurnal temperature range and wind speed changes on pan evaporation change were dominant,they are the primary reasons for the decreasing of pan evaporation in the Northern China in the past 45 years.

• The Valanche,Fractals and the Self-Organized Evolution with Occurrence of Strong Discharge in Thunderstorm
• GOU Xue-qiang;ZHANG Yi-jun;DONG Wan-sheng;QIE Xiu-shu
• 2006 Vol. 25 (5): 849-854. 
• Abstract ( ) PDF (982KB) ( )
• It is considered that avalanche and fractal characterize self-organized evolution of complex system far from equilibrium.By using the ground electrical filed data obtained in the middle of Qinghai-Xizang Plateau region,long-range correlations and multifractal behavior of strong lightning discharges in thunderstorm is investigated with recently developed detrended fluctuation analysis(DFA) and multifractal detrend fluctuation analysis(MF-DFA) method,it is found that the clear long-range persistence and multfractality are involve in the strong lightning discharges,all scaling behavior is consisted with a modified version of the binomial multiplicative cascade multifractal model,the analysis suggest the possible existence of self-organized evolution in thunderstorm discharge.

• Contrast Analysis of Background Error of MM5 3DVAR System in Cold and Warm Seasons in Beijing
• FAN Shui-yong;ZHANG Chao-lin;ZHONG Ji-qin
• 2006 Vol. 25 (5): 855-861. 
• Abstract ( ) PDF (1900KB) ( )
• NMC method is widely used to statistically analyze background error covariances currently.In this paper, based on a month-long series of model forecast fields in August 2002 and February 2003, the background error covariance of high-resolution mesoscale model MM5V3 in cold and warm seasons, which is about to pre-operationally run in Beijing region, is computed using NMC method.The detail climatological statistical characteristics are present as well.The results show that different model variables has different background error characteristics, even the same model variable has different background error characteristics when model resolution or model vertical-level changes.The characteristics are also different in cold and warm seasons, mainly wind field.All those characteristics are corresponding to averaged weather condition in the forecast region.Consequently, 3DVAR should be done respectively for different model domains.In practical run of MM5 3DVAR system in Beijing, method used to compute and update background error covariance should be developed incorporating actual seasonal variation of weather condition.

• A Study on Application OIQC Method to Velocity Dealiasing of Doppler Radar VAD Profile Data
• ZHU Li-juan;GONG Jian-dong
• 2006 Vol. 25 (5): 862-869. 
• Abstract ( ) PDF (330KB) ( )
• Doppler radar has the ability to scan large volumes of the atmosphere at high spatial and temporal resolutions,but ambiguities limit its data using widely.The application of the Optimal Interpolation Quality Control(OIQC) method to the Radar velocity-azimuth display(VAD) data quality control which is presented in this paper.This is based on the ECMWF optimal interpolation quality control technique.Here the simple statistical interpolation method just the Cressman interpolation is adopted.The single variable background error covariance is used because of the characters of the Doppler Radar radial velocity data.And the homogeneous but anisotropic covariance function is adopted in the horizontal orientation according to radial velocity characters.The covariance function in the vertical orientation is Gauss style.For the tested data on the circle and tilt which is formed the VAD wind profile,the Cressman interpolation is used to provide a reference value at every data gate.Comparison the reference velocity with observation data the Nyquist is decided.After the dealiasing,the horizontal wind velocity get by the classical VAD technique at different altitude and the vertical wind profile is obtained.Application this method into WSR-88D data collected during 3 May 1999 tornado outbreak,compares the wind profile with it obtained by wind profiler,Tabary's slope method,Bayes method,Yamada's continuity method.The aliased radial velocity and dealiasing radial velocity images also be presented.All these result show that this method has the ability of unfolding the ambiguity velocity,and it combined VAD method can obtain accurate wind profile from fold data.

• Estimation of Atmospheric Sulfur and Nitrogen Deposition over East China Using Sub-Grid Simulation Scheme
• WANG Ti-jian;ZHANG Yan;YANG Hao-ming
• 2006 Vol. 25 (5): 870-876. 
• Abstract ( ) PDF (671KB) ( )
• The sub-grid scheme for dry deposition was nested into the Regional Acid Deposition Model System(RegADMS) to simulate sulfur and nitrogen depositions over East China.Four different sub-grid schemes and coarse grid scheme(with the horizontal resolution of 75 km) were compared with the fine-grid scheme(with the horizontal resolution of 25 km) to find the best one.As a result,as far as dry deposition velocity was concerned,the sub-grid schemes showed more performance than the coarse grid scheme.For the four subgrid schemes,the best one assumes that sub-grid friction velocity multiplies wind speed is constant.Investigations have showed that the total annual sulfur and nitrogen depositions in East China is 1.92 mt(1 mt=10⁶ ton)and 0.65 mt,respectively,most of which are deposited to soil-plants ecosystem(more than 70%).The sulfur (SO₂ and sulfate) dry deposition accounted for almost 49% of the total sulfur deposition over East China,while the counter part for nitrogen(NO,NO₂ and nitrate) dry deposition is 80%,which suggests that dry deposition is very important in total deposition.In East China,the total sulfur deposition has exceeded the critical load,while nitrogen deposition does not exceed its critical load.

• A Study on the Physical and Chemical Features of Aerosols in the Area South of the Nanling Mountains
• WU Dui;DENG Xue-jiao;YE Yan-xiang;HUANG Hao-hui
• 2006 Vol. 25 (5): 877-885. 
• Abstract ( ) PDF (1272KB) ( )
• The spectrum of mass and water dissoluble ion components of aerosol samples collected in the area south of the Nanling mountains have been analysed.The result show that the concentrations of total mass and all ions of aerosols lie in the middle of average values of clean and urban areas,the distribution has three peaks locating in the huge particles,large particles and sub-micron particles respectively,the main peak is at the huge particles.The distribution of K⁺ ion is the most special,only having one obvious peak at 0.065~1.1 μm.In the aerosol SO₄^2- is the main anion,and Ca²⁺ is the main cation,Comparing with those of country in South China,the concentration of SO₄^2- accounts for the majority of anions,besides the ion concentration double increase.On the other hand,the main features are that the content of NO₃^-,NH₄⁺,remarkably decrease comparing with those in cities over South China.In rainy season either total concentration or concentrations of SO₄^2-,Ca²⁺,Mg²⁺ remarkably decrease comparing with those in dry seasons,showing close relationship with rain scavenging processes.The water dissoluble NH₄⁺,K⁺,SO₄^2- in aerosol exist large in fine-mode particles,their mass median diameters are larger than those in Guangzhou in dry season,but smaller in rainy season.While F^-,Ca²⁺,Cl^-,Na⁺ exist large in coarse-mode particles.Comparing with the soil in South China,the Mg²⁺,Ca²⁺ of aerosol collected at Dayaoshan and Baiyunshan have obvious enrichment in dry season,SO₄^2- also have enrichment to a certain extent,while in rain seasons only Mg²⁺ in Baiyunshan have enrichment.Analyses of ion neutralization,indicate that the aerosol should be acidity in the area south of the Nanling mountains,having low neutralization of acid rain,and this would aggravate losses caused by acid rain.

• The Aerosol Optical Depth over Lanzhou Area Retrieved with a Compared Method Using MODIS Data
• HUANG Ting;CHEN Chang-he;CHEN Yong-hang;ZHANG Wu;ZHANG Lei
• 2006 Vol. 25 (5): 886-892. 
• Abstract ( ) PDF (624KB) ( )
• The dark target method developed by Kaufman is one of methods to retrieve the aerosol optical depth using MODIS data.But there is limitation in getting the surface reflectivity of visible channel.In this paper we demonstrate an experiment with a compared method to study the feasibility of retrieving aerosol optical depth for large particle size.The sensitivity of two day's difference of apparent reflectivity to aerosol optical depth was simulated with 6S model.The aerosol optical depth and particle geometrical mean mass radius over water was retrieved with a LUT using two day's MODIS data.The aerosol optical depth over Lanzhou area was retrieved and the result is close to the sun photometer measurements on the ground,which indicates the method is feasible.

• The Transportation Paths of Water Vapor and Its Relation to Climate Change over North China
• MA Jing-jin;GAO Xiao-qing
• 2006 Vol. 25 (5): 893-899. 
• Abstract ( ) PDF (1904KB) ( )
• By using the HYSPLIT_4 Model and NCAR/NCEP reanalysis data form 1948 to 2003,the interdecadal variations of the water vapor transportation paths over North China in summer(JJA) have been calculated and discussed in this paper.The results showed that the characteristics of water vapor transportation change were obvious.The dominant direction of the water vapor transportation at 850 hPa over North China in summer(JJA) from 1950 to 1970 was from south.In 1970's,the direction of the water vapor transportation became from west and it was from northwest in 1980's.In addition,there was maximum for the vertical integral of vapor fluxes from 1960 to 1964,which began to decrease from 1965.The vapor flux was less and stable since 1977.The variations of the water vapor transportation paths is related with the weaken of summer monsoon over East Asia.The character of water vapor transportation path in North China region in summer months(JJA) is very different from 1950's to 2000's.

• Study on Variety Trend of the Precipitation in the Hetao and Its Vicinity Area in Recent 40 Years
• ZHONG Hai-ling;LI Dong-liang;CHEN Xiao-guang
• 2006 Vol. 25 (5): 900-905. 
• Abstract ( ) PDF (445KB) ( )
• The precipitation variational characteristics of the Hetao area has been analyzed by using the monthly precipition data of 58 meteorologic stations in the Hetao and its vicinity area from the beginning to 2003.The result shows that the precipitation is more in the southeast and less in northwest as a whole,and isopluvial present the trend of the northeast-southwest.the region of the least precipitation is the northwest of Hetao area,while the region of the most precipitation is the southeast.Because of the effect of geography characteristic and Mongolia high pressure and anticyclone of the northeast of Qinghai-Xizang Plateau,the grads of precipitation is greater in the southwest than in the northeast.The precipitation has a better coherence in space,but it has the difference between the south and the north of Hetao area.In recent 40 years the precipitation of the northwest of Hetao area is decreasing by 2%/10a,and the precipitation of the southeast of Hetao area is decreasing by 3%/10a,but at the end of 1990's and the begin of 21 centuries the precipitation of the southeast turn round.The further research indicate: in the Hetao and its vicinity area the precipitation have an osculatory relation with Eurasia snow area.When Eurasia snow area increase in autumn,the precipitation in the Hetao and its vicinity area will increase in the following year,vice versa.

• Spatial and Temporal Characteristics and Change Trend of Climatic Elements in the Headwater Region of the Yellow River in Recent 40 Years
• XU Zong-xue;HE Wan-lin
• 2006 Vol. 25 (5): 906-913. 
• Abstract ( ) PDF (423KB) ( )
• The Mann-Kendall statistic test method is used to estimate the spatial and temporal characteristics and variations trend of sunshine,surface air temperature,precipitation,and evaporation at 13 hydrologic stations in headwater region of the Yellow River from 1959 to 1997.The results show that the trend of sunshine decreased weakly in the study area over the past 40 years,the magnitude of the sunshine decreases from northern to southern parts and the long-term trend decreases from middle to western,eastern,and northern parts.The air temperature remarkably increased over the past 40 years,the magnitude increases from western to eastern,and from southern to northern parts,the long-term trend weakly increases in middle and southern parts,but strongly in northern,eastern,and western parts.The precipitation decreased over the past 40 years,the magnitude of precipitation decreases from southeastern to northwestern parts,the long-term trend decreases in most of the study area.In contrast to the air temperature,the evaporation decreased over the past 40 years,the magnitude decreased from northern to southern parts,the long-term trend decreases in most of the study areas,especially in northern parts.In addition,the linear trends are estimated and the results are briefly presented in this paper.The results which obtained by the two methods coincide well with each other.

• The Detection of a Severe Tornado Event in Anhui with China New Generation Weather Radar
• YU Xiao-ding;ZHENG Yuan-yuan;ZHANG Ai-min;YAO Ye-qing;FANG Chong
• 2006 Vol. 25 (5): 914-924. 
• Abstract ( ) PDF (1606KB) ( )
• Based on the Hefei Doppler weather radar data,the tornadoes occurred in Wuwei county,Anhui province in the night of 8 July 2003 are analyzed in detail.From the night of 8 to the early morning of 9 July,associated with the organized convective rain belts embodied in the large area of stratiform precipitation,several meso-γ-scale vortexes formed along the leading edge of the convective rain-belt within the lower atmosphere.A mesocyclone formed at the south tip of the convective rain-belt led to the severe tornado occurred at 23:20 in Wuwei county,Anhui province.This tornado,ranked F3,killed 16 and wounded 166 persons.The convective system which caused the Wuwei tornado is a classic supercell located at the south end of a convective rainbelt.During the lasting period of the tornado,a TVS formed within the strong mesocyclone,the vertical vorticity associated with the TVS is about 5.0×10^-2/s.This supercell is a low centroid convective system,the above 45 dBz reflectivity region is limited to below 6 km,the severe tornado is the major severe weather,accompanied by heavy rain,without hail.The analysis indicate that,for the Wuwei tornado,a tornado warning could be issued with 8 min lead time,mainly based on the strong mesocyclone on velocity map,illustrating the greatly enhanced capability to detect tornadoes with the deployment of the China new generation Doppler weather radar.The mechanisms for this tornado occurrence are also discussed.

• Analysis on Mesoscale Circulation within a Heavy Rain System Using Doppler Radar Data
• YANG Yi;QIU Chong-jian
• 2006 Vol. 25 (5): 925-931. 
• Abstract ( ) PDF (1036KB) ( )
• A two-step variational method of 3D wind is introduced to analyze the stream structure of a heavy rain event occurred in the Yangtze River and Huaihe regions on 4~5 July 2003 by using the Doppler radar.The result shows that a convergence band long existed in middle and lower levels,which were formed by southwesterly flow and northwesterly airflows,caused the heavy rain.Aloft,the westerly airflow predominated.The convergence in lower levels caused stronger updraft that resulted in the intensification of this rainfall system.Rich moisture was supply to maintain the heavy rain by the stronger southwesterly airflow on the south side of the convergence band.

• Analysis of Echo Character of Doppler Radar for a Severe Convection in the Mid-Part of Gansu Province
• FU Shuang-xi;WANG Zhi-jun;ZHANG Jie;CHEN Qian
• 2006 Vol. 25 (5): 932-941. 
• Abstract ( ) PDF (1700KB) ( )
• Combining CINRAD/CC Doppler radar data with some routine observation data including surface and aerological chart,Yuzhong RW station information,ground-based automatism stations observations and DEM data in the distance of 150 km,the mesoscale weather processes on 18 August 2004 have been analyzed.The results show that the severe convective processes happened under upper level cold and lower level warm advection circumstance and terrain effect belonging to different advection type hailstorm.The herringbone and bow echo shape of reflectivity factor have occurred,adverse wing region and microcyclone appear of average radial velocity,and there are convergence on lower level and divergence on upper level characters in the regions of hail formed.There are strongly circumgyrating and rising air current in the PPI.The strong echo region may be some relationships with convergence region,adverse wind region,microcyclone,VIL region,at the same time,VIL product is well used for region prediction of hail happened.

• Analysis on Raindrop-Size Distribution Characteristics of Maqu Region in Upper Reach of Yellow River
• LI Juan;YOU Lai-guang;HU Zhi-jin;TU Duo-bin;LI Lun-ge
• 2006 Vol. 25 (5): 942-949. 
• Abstract ( ) PDF (1048KB) ( )
• To solve the problem that Yellow River areas is short of water resource,rain enhancement experiments are conducted in upper reach of Yellow River.It is organized by Qinghai Meteorological Bureau in 2000.Analysis of raindrop-size distribution in Maqu region shows that raindrop-size there is big.The result provides experimental foundation for implement of rain enhancement experiment there.On the other hand,the relationship between radar reflectivity factor and rain intensity can be useful to the quantitative measurement of rainfall.What is more,the warm rain process can be useful to precipitation although cold rain process is the main precipitation mechanism over Qinghai-Xizang Plateau.The analysis of raindrop-size distribution can deepen the understanding of cloud physical characteristics over Qinghai-Xizang Plateau.

• Analyses and Tests on Artificial Precipitation Effect of Cloud System in Cold Vortex in Northeast China
• ZHOU De-ping;GONG Fu-jiu;WANG Ji-hong
• 2006 Vol. 25 (5): 950-958. 
• Abstract ( ) PDF (546KB) ( )
• Based on the regular and characteristics of precipitation processes of cold vortex in Northeast China and observational data of Liaoning meteorological observation networks,using the method of ROCMACS(Regression of Compartmentalization of Moveable Target and Control Areas after Cloud Seeding),the effect of artificial precipitation operation of cold vortex in Northeast China are comprehensively analyzed.The results are as follows:(1) The average precipitation enhancement effect in Liaoning Province during June and August from 1992 to 2004 is 22.4%.(2) The reliability over 95% prove that the artificial precipitation enhancement have positive effect.(3) The way and position of seeding is reasonable basically,and the seeding is resultful.

• A Numerical Research about Initial Disturbance of Hail Cloud
• ZHOU Ying;WEN Ji-feng
• 2006 Vol. 25 (5): 959-963. 
• Abstract ( ) PDF (353KB) ( )
• To take adequately account of the mountain feature in low latitude and plateau of Guizhou province,a three-dimensional dynamical numerical model over complex terrain is designed to simulate initial disturbance resulting from the thermodynamic and dynamic nonuniformity of underlying surface.On the basis of the initial disturbance,a completely elastic three-dimensional hail cloud catalyst numerical model is used to forecast the hail weather.The rate of empty forcasting decreases from 42.9% to 22.6%.The summary rate of forecast increases from 80.2% to 92.3%.

• Quasi-Meridional Precipitation Belt in East China and Its Formating Cause Analysis
• TANG Mao-cang;LIU Miao;ZHU De-qin;LI Dong-liang
• 2006 Vol. 25 (5): 964-968. 
• Abstract ( ) PDF (630KB) ( )
• According to clear quasi-meridional geological structure in East China,the quasi-meridional precipitation is classified as three types,they are(1) 3e,there is rainy in Yanlu rapture and coastal areas at east of Yanlu,and there is dry at west areas of Yanlu;(2) 3m,there is rainy near north-south seismic belts in center China,and there is less rain at east of Taihang mountain-Wuling mountain;(3) 3d,there are two rainy belts or two dry belts in East China.Almost all of the meridional precipitation belts occurred in April during summer when rotation of the earth is slower(ΔLOD0) and when such slower is speed-up(Δ² LOD0).This gives an important index for prediction of meridional precipitation in flood season.

• Analyses on Circulation Characteristics of Precipitation Anomalies in Flood Season of Liaoning
• YANG Wen-yan;WANG Qian-qian
• 2006 Vol. 25 (5): 969-974. 
• Abstract ( ) PDF (1265KB) ( )
• Based on the analysis of climatic characteristics of precipitation in flood season of Liaoning,the circulation characteristics infulence on precipitation in flood season Liaoning are analyzed.The rsults are as follows:(1) precipitation shows the decreasing trend and remarkable interannual and interdecadal variations in flood season in the last 44 years.(2) precipitation anomalies in flood season have a good correlations with southwest and southeast summer monsoon,polar vortex,west wind trough,the subtropical high over West Pacific and South Asia High.