Current Issue

• A Number of Advances of the Research on Midlatitude Mesoscale Convective Systems
• CHENG Lin-sheng;FENG Wu-hu
• 2002 Vol. 21 (4): 337-347. 
• Abstract ( ) PDF (557KB) ( )
• Mesoscale convective systems(MCSs) are in close relationship with many severe meteorological disasters,particularly,heavy rainfall flooding in China.A briefly comprehensive review for a number of advances in the research of midlatitude MCSs is presented in this paper.In which include:The temperal and spatial distribution of MCSs;the mean genesis environments of MCSs;the organizational modes and upscale evolutions of MCSs;the interactions between developing MCSs and their environments;the dynamics and instability of MCSs;the numerical simulations of MCSs;the observations and simulations of MβCSs and MγCSs;the conceptual model of MCSs;the observational projects of for studies on structure and mechanism of MCSs.We wish this paper is helpful for the reader interested in it to further understand some advances of the research concerning the genesis,developments,structures,mechanisms and conceptual model of midlatitude MCSs.

• Regional Characteristic Calculation of Lightning Production of Nitrogen Oxides(LNO _X)(Ⅰ):Theory and Calculation Method
• ZHANG Yi-jun;YAN Mu-hong;DU Jian
• 2002 Vol. 21 (4): 348-353. 
• Abstract ( ) PDF (249KB) ( )
• The general research situation on nitrogen oxides produced by lightning were introduced and its production mechanism,characteristics,processes of transportation and the role in global climate change were included.The mechanism,transportation,calculation methods and errors of lightning production nitrogen oxides for regional thunderstorm were mainly narrated.The calculation methods and selection of parameter were briefly introduced for the regional characteristics calculation of lightning production nitrogen oxides.

• Numerical Study For Convection Cells Self-Organization
• XUE Ju-kui;HU Yin-qiao
• 2002 Vol. 21 (4): 354-358. 
• Abstract ( ) PDF (276KB) ( )
• For a shallow convection boundary layer system,convection cells self-organizing process is studied according to the nonlinear thermodynamic theory.The relationship between the entropy budget and cells organization process is revealed clearly.As a result,the catastrophic lose of stability in the system triggered the occurence of cells.The cells pairing and merger process can be dynamicly viewed as cells nonlinear self-organization.While in corresponence with this process,the negative entropy flow gained from the environment is the basic thermodynamic reason of the cells self-organization and final maintain of ordered structure cells.

• Analyses on Circulation Patterns and Water Vapor Fields of Snow Disaster Weather in Eastern Pasture Areas of Qinghai-Xizang Plateau
• LIANG Xiao-yun;QIAN Zheng-an;LI Wan-yuan
• 2002 Vol. 21 (4): 359-367. 
• Abstract ( ) PDF (586KB) ( )
• The snow disaster weather occurred in winter and spring,is one of crucial catastrophe weathers in eastern pasture area of Qinghai-Xizang Plateau(QXP).In this paper,the circulation patterns of the winter and spring snow disaster weathers over the area and some of their water vapor fields have been analyzed utilizing the historic synoptic charts and the analyzed gridded data of global model T106L19 of National Meteorological Center of China.The main conclusions are as follows:(1) There are four main circulation patterns causing snow disaster weathers in 500 hPa over the area in winter and spring.They are the pattern with the ridge to the north and the trough to the south of QXP,the one with ridges in Ural Mountain,the one with step-like troughs,and the one with the troughs in China-Kazakstan boundary.(2) The significant increasing of air column precipitable water happens when the strong snowing weathers occur.The main snowy regions are in well agreement with the convergence regions of water vapor fluxes.(3) The water vapor comes mainly from the Bay of Bengal when snow disaster weather occurs.

• The Statistic Characteristics of Radar Echo and Precipitation and Some Thermodynamic Variables in Qinghai-Xizang Plateau
• FENG Jin-ming;LIU Li-ping;WANG Zhi-jun;CHU Rong-zhong
• 2002 Vol. 21 (4): 368-374. 
• Abstract ( ) PDF (349KB) ( )
• Using Doppler radar data,sounding data and precipitation data of Qinghai-Xizang Plateau in 1998,we calculated and analyzed the statistic characteristics of radar echo and some thermodynamic variables and precipitation in Qinghai-Xizang Plateau.After monsoon onset in the middle of June in Qinghai-Xizang Plateau,the convective activity strengthens distinctly in cloud.According to the diurnal variation,the intensity of convective activity in cloud attains to the maximum at 02:00 of local time approximately.The reflectivity and area and top of radar echo augments greatly since monsoon.The precipitation also increases greatly.Some thermodynamic variables is distinctly altered.The convective condensation level decreases and parcel energy increases generally.

• A Numerical Study on Charge Distribution in Leader Channel of Cloud-to-Ground Lightning Discharges
• YU Ye;QIE Xiu-shu;YUAN Tie
• 2002 Vol. 21 (4): 375-380. 
• Abstract ( ) PDF (257KB) ( )
• A consistent physical model that describes the relationship between cloud charges and lightning was produced and used to simulate the charge density in the leader channel based on the bi-directional leadermodel.The results indicated that the total charge in the leader channel increases when it closes to ground.It was found that the average charge density in the leader channel just before it reaches the ground is 1.5×10 ^-3C·m ^-1,and the total charge in the leader channel is 14.8 C.The induced charge density in the leader channel is 0.34×10 ^-3C·m ^-1,which takes about 20% of the total charge in the leader channel,indicating that the most common way by which charges stored in the leader channel was the transporting of cloud charges.

• A Preliminary Study on Seasonal Variation of Microclimatic Characteristic of City Courtyard
• ZHANG Yi-ping;LI You-rong;LIU Yu-hong;MA You-xin;WANG Jin-xin
• 2002 Vol. 21 (4): 381-388. 
• Abstract ( ) PDF (340KB) ( )
• By comparing and analyzing meteorological observation data of grassland,roof and road in Kunming,a low latitude city,the variations laws and difference characteristics of microclimate on the different underlying surfaces of city were discussed.The results indicated that the variation tendency of meteorological elements on different underlying surfaces were similar to that of macroclimate andmaximum value of meanmaximum air temperature appeared in later stage of dry season,daily range of air temperature was greater in dry season and less in rain season,the value of relative humidity was greater in rain season and less in dry season,but variation of relative humidity was greater in rain season and less in dry season.The variation value of wind speed were greater in dry season and less in rain season.By comparing meteorological elements of different underlying surfaces,we could draw the conclusion about variation characteristics of yearly,that is,in contrast with grassland,maximum air temperature of roof and road was higher and minimum air temperature was lower,variation of air temperaturewas greater,relative humidity was lower and wind speed was greater.The difference is greater in dry season and less in rain season.

• A Model Study of Land Biosphere about High-Cold Meadow Ecosystem and Its Application
• YAO De-Liang;SHEN Wei-ming;ZHANG Qiang;ZHOU Xing-min;SHEN Zhen-xi
• 2002 Vol. 21 (4): 389-394. 
• Abstract ( ) PDF (264KB) ( )
• A land biosphere model suitable for the high-cold meadow ecosystem is improved.The physical reasons of temperature change and moisture movement in the mathematical model are also analyzed.It illustrates the effect of climate on land surface energy exchanges,gives the calculating methods of net radiotion and evapotranspiration,proposes Euler implicit scheme with two-order accuracy and presented the climate conditions and field measurements in Haibei ecosystem station.Finally,numerical simulation is carried out by the model forwater-heat exchange processes of soil-vegetation-atmosphere in high-cold meadow area of the north of Qinghai Province.Numerical result coincides with measuring data.

• New Evidences for the Relationship between Climate Change and Geomagnetic Field
• GAO Xiao-qing;LIU Yan-xiang;DONG Wen-jie;TANG Mao-cang
• 2002 Vol. 21 (4): 395-401. 
• Abstract ( ) PDF (309KB) ( )
• It is well known that there is good relationship between climate change and geomagnetic field.In this paper we attempt to describe a possible physical explanation.The geomagnetic field data and global mean temperature in the past 600 years have been used for analyzing the relationship between them in this paper.Results show that there is a good correspondence between them,and the change of geomagnetic field is prior to the change of global temperature.From the trend of geomagnetic field change,it seems that the global warming would slow down in the early part of 21 century.The comparison analysis between the thermal field(geothermal belts,volcano distribution and soil temperature field) in the shallow layer of the ground and Joule heat field on Asthenosphere-Lithosphere Boundary(ALB) shows that they matches each other very well in spatial characteristics.It implies very possible that the thermal field in the shallow layer is the reflection of the Joule heat field on ALB,and geomagnetic field could influence climate change through the release of Joule heat.

• Summary on Wind Tunnel Experiment Study of Sandstorm Electrification
• ZHANG Hong-fa;QU Jian-jun;YAN Mu-hong
• 2002 Vol. 21 (4): 402-407. 
• Abstract ( ) PDF (271KB) ( )
• Using a big wind tunnel laboratory equipment,electric field intensity,electric potential and sand particle charge were simulated and measured for different sand sample and wind velocity.The result show that the blown sand have electrification effect,the most of electric fields are nagetive,maximun average electric field intensity is-29 kV·m ^-1,electric potential is 120 mV.The blown sand electrification increased with increase of wind velocity and decrease of sand particle size.

• Pulse Corona and a New Mechanism of the Negative Stepped Leader in Cloud-to-Ground(CG) Lightning Discharge
• GOU Xue-qiang;ZHANG Yi-jun
• 2002 Vol. 21 (4): 408-413. 
• Abstract ( ) PDF (258KB) ( )
• Based on latest observation,we make an assumption that the bright pulse of negative stepped leader in the CG lightning discharge is not initiated by a slow and faint streamer(pilot streamer),but is initiated by a fast and instant corona(pulse corona).Thus a new conceptual model of stepped leader was proposed and a simple numerical model was set up.The characteristic parameters of streamer time intervals and the stepped length were discussed.The characteristic radiation pulse of stepped leader was explained more clearly and the bidirectional propagation process of the stepped pulse was analyzed.The result is basically agreed with observation.

• Study on Mesoscale Model Cumulus Parameterization Scheme over Low Latitude Plateau
• DENG Song;JU Jian-hua;Lü Jun-mei
• 2002 Vol. 21 (4): 414-420. 
• Abstract ( ) PDF (332KB) ( )
• It is very important to design cumulus parameterization schemes in study of mesoscale numerical model over low latitude plateau.Furthermore,the design schemes of the vertical heating profile and the moistening coefficient are two important problems in Kuo type cumulus parameterization schemes.In this paper,we designed various amending cumulus parameterization schemes from the points of the vertical heating profile and the moistening coefficient to make numerical experiments.The experimental result show that θ _se method used in vertical heating profile and index scheme in moistening coefficient are more suitable for mesoscale numerical model over Yunnan low latitude plateau.The moistening coefficient over low latitude plateau is larger than that in eastern coastal regions and on some plains.The simulated effect of mesoscale numerical model over low latitude plateau will be improved after we consider the influence of steep topography of plateau on the base of improving cumulus parameterization scheme.

• Local Similarity in the Tower Layer over the Forest and Wetland-Forest
• LI Ping-yang;JIANG Wei-mei;MIAO Shi-guang
• 2002 Vol. 21 (4): 421-426. 
• Abstract ( ) PDF (257KB) ( )
• Local similarity of non-dimensional quantity is examined using turbulence observations at meteorological towers in forest and wetland-forest.The empirical constants of similarity functions,which are dependent on ζ _l only,are obtained under stable and unstable conditions.The results show that the turbulence structure in the tower layer of the atmosphere over either forest or wetland-forest could be orderwell by local similarity scales u _*l, T _*l, q _*l, L _*l.It is of interest to find σ _T/ T _*l seems to be related with the H,and the data points were obviously separated for different values of H.The lower data denoted by symbol '·' correspond to the larger values of H,which show a better similarity relation;It is the same condition between σ _q/ q _*l and λE.

• Monitoring Analysis of Winter TSP over Chengguan District of Lanzhou and Their Effects on Radiation
• XI Xiao-xia;QUAN Jian-nong;CHEN Chang-he;ZHAO Xiu-juan
• 2002 Vol. 21 (4): 427-431. 
• Abstract ( ) PDF (215KB) ( )
• Climatic effect of aerosol is a key link and heated front topic in the studies of global climatic change and numerical simulation,as well as the basis for understanding the climatic change mechanism.For this,we monitored the TSP and solar radiation at different heights in Chengguan district of Lanzhou city and Gaolan mountain,respectively,in winter(December 1~10,1999),and tried to reveal the distribution of quality concentration of aerosols in air and its effects on solar radiation.The results are as follws:(1) The pollution of TSP was very serious in winter in Chengguan district,the daily quality concentration of TSP was 0.9697mg·m ^-3,and it can be 3.23 times for the second grade standard;(2) The impact of TSP on solar radiation is significont,comparing with Gaolan Mountain,the lower-level atmosphere decreases the solar direct radiation by 62.5%,increases solar diffuse radiation by 50.6%,the total solar radiation is reduced by 14.1%;(3) TSP affects the development of the lower-level atmosphere temperature inversion layer by absorbing solar radiation,which further has an effect on the dispersion of TSP.