Plateau Meteorology

Current Issue

28 February 2007, Volume 26 Issue 1   
  • The Numerical Simulation of Orographic Cloud Structure and Cloud Microphysical Processes in Qilian Mountains in Summer. Part (I):Cloud Microphysical Scheme and Orographic Cloud Stucture
  • LIU Wei-guo;LIU Qi-jun
  • 2007 Vol. 26 (1): 1-15. 
  • Abstract ( ) PDF (1559KB) ( )
  • The ARPS mesoscale model is improved by modified its cloud microphysical scheme.Three new predictands and their microphysical processes, including the number concentration of cloud ice(Ni) and artificial ice crystal(Nia) and the mixing ratio of artificial ice crystal(Qia),are introduced into the model.Deposition and condensation-freezing nucleation(pidcf),contact-freezing nucleation(pictc),ice multiplication(pimult) and accretion of cloud ice by cloud water(piacw) are added to the cloud microphysical scheme.The equations of autoconversion of cloud water to form rain(praut),condensation and evaporation of cloud water(svc),deposition of cloud ice(dep) and sublimation of cloud ice(sub) are improved.In addition,three kinds of cold cloud seeding scheme are developed in model,and the seeding materials include ideal artificial ice crystal and AgI catalyst.Two cases of Qilian mountains area orographic cloud in summer are simulated by the improved ARPS model.The characteristics of cloud development,cloud dynamic, precipitation and cloud microphysical structure are investigated.Those cases study suggest that orographic cloud is greatly influenced by topography.Forced lifting of topography prolong cloud life,widen cloud field and promote the development of cloud convection.Because of orographic influence,precipitation area is expanded,and precipitation duration is prolonged,and precipitation intensity and grossed are also changed.Furthermore,the orographic influence also result in the variation of cloud microphysical characteristic,such as the grosses,distribution and life time of water substance in cloud.
  • Analysis on the Initial Stage of Intracloud Discharge over the Qinghai-Xizang Plateau
  • SHE Hui-Lian;DONG Wan-Sheng
  • 2007 Vol. 26 (1): 55-61. 
  • Abstract ( ) PDF (640KB) ( )
  • Radio frequency observations of intracloud lightning(IC) over the Qinghai-Xizang Plateau have been made using a broadband interferometer system in the summer of 2003.The spatial and temporal variations of radiation sources and electric field change of IC discharge have been analyzed in this paper.The result indicate that the IC discharges occur between the lower positive and upper negative charge regions when the polarity of surface electric field of thunderstorm passing is positive,but the upper positive charge doesn't participate in discharge.Although different flashes have differently very structures,the initial stage of discharge has the similar physical process.The IC discharge always initiates at the negative charge region,the channels of IC lightning propagate downward during initial stage within tens of milliseconds,and the downward speed of the lightning channel is about 1.14~1.72 105m/s.In the lower positive charge region,the channel of the flash can vertically propagate,and it also can levelly propagate.The radiation which occurred in the lower positive charge is very complicated.There are much more radiation points in the lower positive charge region than in the upper negative charge region.
  • On Study of Interdecadal Prediction of Drought/Flood in Northern China
  • WANG Ge-li;YANG Pei-cai;WANG Yong-qing;ZHU Ya-fen
  • 2007 Vol. 26 (1): 67-74. 
  • Abstract ( ) PDF (760KB) ( )
  • The most of time series from the real world,especially those representing climate processes,are too short to satisfy the ideal data length requirement.Too short a history cannot give a full description for the state distribution of the dynamic system.This difficulty is usually referred to as the "data bottleneck" problem for short time series analysis.In order to solve the above problem,some atmosphere scientists have suggested the reconstruction of the dynamic system with observation data from different spatial positions.They have once applied this idea to estimate the dimension of climate attractors and achieved some successes.In this study,a technique of spatial-temporal series analysis prediction model is presented based on reconstruction the state space theory and embedding theory.By means of this technique,some prediction experiments for the decadal-scale drought and flood and their extreme frequencies are carried out in this paper according to the data of 534 years of drought/flood series in northern China.Comparing with the single-variable time series,the selection range of the nearest neighbor set is not only limited in the sub-trajectory in which the current point lies,but also extended to the whole attractor.This technique can be used to a certain extent to improve the ergodicity of the single-variable time series.
  • Impact Assessment of Urban Sub-Domain Planning on the Atmospheric Environment
  • MIAO Shi-guang;WANG Xiao-yun;JIANG Wei-mei;XI Wen;JI Chong-ping;LIU Feng-hui;CHEN Xian-yan
  • 2007 Vol. 26 (1): 92-97. 
  • Abstract ( ) PDF (256KB) ( )
  • In responese to the planning office's demands to analyze and evaluate different layouts,based on an urban sub-domain scale meteorology and pollutant diffusion model,a set of index system and evaluating scheme of impact assessment of urban sub-domain planning on meteorology and atmospheric environment is set up.As an example,two layouts of a sub-domain in Beijing are assessed.It shows that,because there is a wide road with grass and trees in east-west direction in the second planning,the road becomes an important channel for airflow.And the wind speed around the road is bigger,air temperature is lower,pollution is weightless,so the strip domain around road is good to the improvement of meteorology and atmospheric environment in the whole sub-domain.In a word,it is available and necessary to evaluate the impact of urban sub-domain planning on meteorology and atmospheric environment. The six assessment indexes(body comfortable degree,walker comfortable degree, ground pollutant concentration,pollutant concentration below the highest building,pollutant concentration on the surface of buildings and diffusion capability) and their weighted factor 0.2,0.1,0.1,0.1,0.1 and 0.4,respectively are firstly pointed out,finally the impact of urban sub-domain planning is evaluated by taking the weighted everaging.and the evaluating method of weighted average is reasonable and practical.
  • Case Study of Precipitation Cloud Structure Viewed by TRMM Satellite in a Valley of the Tibetan Plateau
  • FU Yun-fei;LI Hong-tu;ZI Yong
  • 2007 Vol. 26 (1): 98-106. 
  • Abstract ( ) PDF (1329KB) ( )
  • The precipitation cloud structures of a rain event in a valley area(29.49°~30.13°N,95.08°~96.89°E)of southern Tibetan Plateau detected by TRMM satellite at 13:05(UTC) on May 4,1999 are studied by using standard TRMM data sets of precipitation profile,infrared radiant temperature,microwave brightness temperature at high frequent channel and flash together with topographic data as well as NCEP data.Results indicate that this precipitation cloud is a strong local convective precipitation system induced by the topographic forcing effect.The horizontal scale of the precipitation cloud is about 20 km.In vertical direction, the cloud shape extends outwards from the bottom of the valley to the upper like "mushroom". Results also show that the maximum rain rate is more than 100 mm·h-1,which is located in the lower level of the cloud within the valley.Above the valley,the strong convective cloud body stretches in the wide downwind region where weak precipitation is produced.The studies expose consuming variations of IR radiant temperature from cloud top and microwave brightness temperature from cloud body corresponding to intensive surface rain rates of the strong convective precipitation cloud.Furthermore,the analysis illustrates the very inhomogenous distributions of flash frequency,duration and radiance energy in the cloud although relative small differences of cloud tops and ice contents near each flash location.Synoptic analysis shows that the rain event is produced by a weak low pressure trough eastward moving in 500 hPa over the Plateau 13 hours before the rain event detected by TRMM satellite,which induces convergence in the lower atmosphere,divergence in the middle and upper atmosphere,as well as increases of atmospheric instability.
  • Primary Analyses of Upper-Air Temperature Changes in China in past 40 years
  • XUE De-qiang;TAN Zhe-min;GONG Dian-li;WANG Xing-tang
  • 2007 Vol. 26 (1): 141-149. 
  • Abstract ( ) PDF (1391KB) ( )
  • Based on the temperature data from the surface to the 10 hPa levels in China at 28 radiosonde stations in 1961-2000,the seasonal variation and long-term trend are studied.The main results are as follows: The seasonal evolution features between surface and 200 hPa and 100 hPa levels are different,e.g.,from surface to 200 hPa the hottest month is July,the coldest month is January,but above 100 hPa levels the result is the oppositive.In late 40 years,the temperature in the lower troposphere significantly increases over almost the country except for south-west China,but it decreases in both upper troposphere and lower stratosphere(especially on 50 hPa levels).The influences of major volcanic eruptions on upper temperature of low latitude and mid-high latitude regions of China are different.In 26 months after volcanic eruption stratosphere temperature is positive abnormaly in lower latitude region,especially from seventh to eighth months the warming is remarkable.Troposphere temperature is cooling in 6~7th months and 16~27th months,the intensity of first cooling period is larger.In middle-high latitude regions,the stratosphere temperature has two obvious warming periods in 1~16th months and 20~29th months,but it is cooling in 17~19th months.The troposphere temperature is cooling in 2~5th months,14~18th months and 21~30th months. The intensity of third cooling period is larger.
  • Variation of Diurnal Temperature Range in China in the Past 50 Years
  • CHEN Tie-xi;CHEN Xing
  • 2007 Vol. 26 (1): 150-157. 
  • Abstract ( ) PDF (330KB) ( )
  • The spatial distribution and time series of diurnal temperature range(DTR) in China are analyzed using the daily temperature data from 1950 to 2001.The relations among the maximum and minimum temperature and the mean temperature are discussed for their possible influence on DTR.The analyzed results show that DTR was decreased in China in the last 50 years.The average decrease of DTR in the high latitude is larger than that of in low latitude.The DTR in the same region or different regions have the different features in seasonal changes.In the northern China the maximum decrease of DTR is in winter,and then spring and autumn,the minimum,is in summer.In Huang-huai and Yangtze River reaches the maximum decreases of DTR are in summer and spring.In South China the maximum of DTR is in winter.On the average,the DTR is decreasing,and this decreasing is more significant in high and middle latitude regions than in low latitude.For the regions that are in the same latitudinal zone the trends of DTR changes are different because of different geographical backgrounds.The DTR has obvious seasonal change and shows a fast decrease in winter and slow decrease in summer in most regions of China,especially in Qinghai-Xizang Plateau and Xinjiang the features of DTR change are quite different from those in the eastern China.
  • Improved Wet Q Vector's Analytical Method and the Mechanism of Meiyu Front Rainstorm Genesis
  • YUE Cai-jun;DONG Mei-ying;SHOU Shao-wen;YAO Xiu-ping
  • 2007 Vol. 26 (1): 165-173. 
  • Abstract ( ) PDF (466KB) ( )
  • By means of the observed weather data and the intensive simulation product data by modified MM4 model,improved wet Q vector(Q*) and Q*vector partitioning,a typical Jiang-Huai Meiyu event beginning from 20:00 on 5 to 20:00 on 6 July 1991 is diagnosed in detail.The results show that the convergence field(CF) of Q* divergence(Q*D) at 600 hPa to precipitation intensity,occurring region and their inhomogeneities at same time have a good indicator activity.The divergence fields are alternately distributed in vertical direction with the related convergence ones throughout the rainstorm process,whereby the secondary circulation(SC) forcing is likely to be an important factor inducing Meiyu front heavy rainfall genesis(MFRG).Furthermore,the Q*vector partitioning has more important diagnostically function than that totalQ*,which leads to a meaningful scale separation of vertical motion(VM) corresponding to torrential rain and is thus more favorable for evaluating the potential physical mechanism for MFRG.For VM,CFs of Q*D indicate different forcings from one phase to another of the rainstorm.Based on above,we depict a possible physical mechanism and provide a concept modefor MFRG:In original atmospheric state,the spatial inhomogeneities of large-scale vapor and VMmake for convergence of synoptic scale Q*D field,which,in turn,forces SC,leading to CF of mesoscale Q*D such that the SC forcing results in MFRG genesis.
  • Numerical Simulation and Diagnosis Research of a Heavy Rainstorm in Mid-and North-Parts of Zhejiang in Pre-flood Season
  • XUE Gen-yuan;CHEN Li-fang;ZHU Xiao-ming
  • 2007 Vol. 26 (1): 176-186. 
  • Abstract ( ) PDF (1662KB) ( )
  • After diagnosing and analyzing the heavy rainstorm occurring on 30 May,2004,which is infrequent when the rain belt moves towards the north in the South China in the pre-flood season through the meteorological dynamics,the mesoscale numerical simulation method is applied to analyze the heavy rainstorm.By researching the macroscale circumfluence and the meso- and micro-scale system's physical mechanisms and the environment conditions,the main results are obtained.The front of the pre-flood season has the gradients of temperature and humidity at the same time.There was the deeper and cold trough from the northwestern China to the Japan Sea.The low vortex develops in the middle reach of the Yangtze River and it is also related with the warm shear-line,which is in favor of forming the mesoscale system.The thick non-divergence level and the convergence in the medium-level offers the advantageous conditions to the birth of squall line.The core of the strong wind locates to the west of the hollow trough which makes the convergence in front of the trough,which is the key to generate the squall line.The Bangladesh Gulf,the West Pacific and South China Sea are all the sources of the water vapor which make such the heavy rainstorm.The strong summer wind and the enhancement of the subtropical high pressure lead to the rain belt locating partial north.The occurrence of the sensitivity of water vapor to the torrential rain is ahead of the vorticity,divergence and the vertical speed,et al.

NewsDownloadMore+More+

DynamicsVideo InformationMore+More+

Links E-journal More+ More+

Official Wechat

QQ Group Chat

The system is designed and developed by Beijing magtec Technology Development Co., Ltd. with technical support: support@magtech.com.cn