Current Issue

• Numerical Study on Three-Dimensional Conditionally Symmetric Instability of "96.1" Snowstorm Event
• WANG Wen;CHENG Lin-shing
• 2002 Vol. 21 (2): 225-232. 
• Abstract ( ) PDF (1462KB) ( )
• Using the output data of a MM4 mesoscale numerical model which fairly well simulated the developing structure and the evolution of the "96.1 "snowstorm event over Qinghai Xizang Plateau,a nonlinear and non zonally non parallel basic flow symmetric instability(SI) models and simulation system were developed to validate the possible effect of conditional symmetric instability(CSI) on the formation of the snowstorm process,the results showed that in a developing model of two dimensional nonlinear SI in a three dimensional basic flow with proper parameters,the use of localized perturbation of streamfunction or potential temperature resulted in circulations forming which slant to south with height in y- z cross section by symmetric instability and are vertical in the along front direction by nonlinear transversal wave instability,have samilar results as in literatures ^[2,10].These circulations were tilted in the horizontal plain relative to y-coordinate,and the three dimensional disposition in the fields of the streamfunction and vertical velocity is consistent with the evolution of the "96.1" snowstorm,that means the two dimensional nonlinear symmetric instability in three dimensional basic flow is a possible explanation for the organization of the "96.1" snowstorm.

• Remote Sensing Retrieval of Surface Monthly Mean Albedo in Qinghai-Xizang Plateau
• XU Xing-kui;LIN Zhao-hui
• 2002 Vol. 21 (2): 233-237. 
• Abstract ( ) PDF (854KB) ( )
• The differences of land surface feature and physical characteristic are mainly reason that cause anisotropic distribution of albedo,it also is the reason that form areal climate.In this paper,using the bidirectional reflectance models and NOAA14-AVHRR data,we retrieved the monthly mean albedo in 1997,and analyzed the result.The type of land surface cover obviously change in every year because of the creativity of human.This inevitably makes environment to modify and lastly lead to global climate change though the convection of large scale atmospheric circulation.So,the land suface albedo is studied that has important scientific sense.

• Characteristics of Atmospheric Heating Field over Northern Qinghai-Xizang Plateau
• JI Guo-liang;GU Ben-wen;Lü Lan-zhi
• 2002 Vol. 21 (2): 238-242. 
• Abstract ( ) PDF (356KB) ( )
• The intensity of atmospheric heating field over the Northern Qinghai Xizang Plateau is calculated by usingthe data observed at Wudaoliang and some experimential formula.The results show that the atmospheric heating fields act as heat source from April to August over the Northern Qinghai Xizang Plateau and theyactas heat sink from October to February,transformation period in March and September,respectively.The annual means of atmospheric heating field acted as heat sink in 1994 and 1995 but they acted as heat source in 1996 and 1997.The interannual changes of intensity of atmospheric heating field are determined mainly by the interannual changes of surface sensible heat flux.

• Preliminary Study on Circulation Cause of Abnormal Rich Precipitation in and to the South of Yangtze River in Summer of 1999
• ZHANG Pei-qun;HE Min;XU Li
• 2002 Vol. 21 (2): 243-250. 
• Abstract ( ) PDF (601KB) ( )
• Circulation characteristics associated with abnormal rich precipitation in and to the south of Yangtze River basin in summer of 1999 were discussed.The following circulation characteristicswere noticed:During the sustained stage of La Niña period,the intensity of WestPacific subtropical high(WPSH) was below normal with its position more moving northward and eastward.The tropical monsoon over South China Sea was stronger in earlier summer,but weaker later.In upper troposphere,South Asia anticyclone ridge and TUTT located something south.Meanwhile,in lower troposphere,the enhanced transportation of water vapor was formed by the cyclonic abnormal circulation over mid-to low-reach of Yangtze River and to the south of Yangtze river valley.In the summer,the continental high persisted in the mid latitude region of Asia.Mid-and low-latitude circulation anomalies synthetically cause the flooding around and to the south of Yangtze river basin.

• The Seasonal Characteristics of Climatic Change Trend in China from 1951 to 1997
• CHEN Wen-hai;LIU Yan-xiang;MA Zhu-guo
• 2002 Vol. 21 (2): 251-257. 
• Abstract ( ) PDF (978KB) ( )
• Based on the data of temperature and precipitation of 160 stations in China from 1951 to 1997,the different seasonal variation trends and their seasonal differences of temperature and precipitation were analyzed,and significance test also was carried out.The results indicate that there is a large seasonal difference of variation trend in China,and that there are warming trend in most areas of China in winter and spring,but cooling trend in summer.In autumn,the intensity and extent of temperature variation is smaller than that in other seasons.Finally,the annual trends of surface temperature and precipitation were analyzed.

• Numerical Simulation Experiment of Torrential Rain Event in East of North-West China
• WANG Jin-song;LI Yao-hui;KANG Feng-qin;ZHANG Hua
• 2002 Vol. 21 (2): 258-266. 
• Abstract ( ) PDF (730KB) ( )
• Using the two way nested grid mesoscale model(MM5),the torrential rain event east of north west China on the first ten days of July in 1998 is simulated,and a series of sensitive experiments are carried out.It is shown that the MM5 model can successfully simulate the torrential rain and the development of the mesoscale system which related to the torrential rain;the latent heating of large scale and cumulus convection scale is a main factor in the precipitation event,latent heat release will lead to the high level atmosphere divergence and the low level atmosphere convergence,and enhance the vertical motion,and result in the heavy rain;the low level vapor content in different regions at initial time directly affects on the torrential rain,and it is the vapor source of the torrential rain;the vertical transportation of surface vapor and sensible heat supplies the development of the torrential rain with the energy.

• A Study of Ecological Environment in Heihe Valley Area through Meteorology Satel lite Monitoring
• GUO Ni;YANG Lan-fang;WANG Juan-li
• 2002 Vol. 21 (2): 267-273. 
• Abstract ( ) PDF (440KB) ( )
• The precipitation and agricultural meteorological data for 1989 and 1998 are similar.The vegetation,snow and water in Heihe valley were identified using data from NOAA meteorology satellites in 1989 and 1998.Vegetation index,snow and water areas were calculated on the basis of corresponding analysis.The changes of vegetation index and snow of upper reaches,oasis area of middle reaches and water areas of lower reaches of Heihe valley were also analyzed.The results show that the vegetation of upper and lower reaches of the river are degenerating,the oasis area and vegetation index of middle reaches of the river are increase.The results also show that the changing features of snow area of upper reaches of Heihe valley in 1998 is similar to in 1989,the velocity of snow melting in 1998 is faster than in 1989 and the area of the lake is diminishing severely.

• Precipitation Characteristic and Interception of Forest in Qilian Mountain
• CHANG Xue-xiang;ZHAO Ai-fen;WANG Jin-ye;CHANG Zong-qiang;JIN Bo-wen
• 2002 Vol. 21 (2): 274-280. 
• Abstract ( ) PDF (1039KB) ( )
• The long term precipitation characteristic and forest entrapment were studied at Sidalong station,Qilian Mountains.The annual average precipitation is 433.6 mm(from 1972 to 2000),and varied from 326.4 mm to 539.7 mm,annual precipitation falls in summer is 65.70%.Precipitation is altered in different altitudes,its tendency increase 4.45% of the amount with altitude arising per-100 m.The average entrapment rates are 37.5%,31.7% on canopy entrapping precipitation of Picea crassifolia forest and Sabina Przewalsskii forest,the average entrapment rate of brush forest even is as high as 66.5%.When the rainfall is intensive,its average entrapment rate gradually diminished in Picea Crassifolia forest.When the amount of precipitation is 18.67 mm,the amount of canopy entrapment of Picea Crassifolia forest is 14.72 mm.The trunk runoff of Picea crassifolia is 0.51% of the amount of precipitation and its trunk runoff began when the amount of precipitation is over 12.0 mm.The litter entrapment precipitation gradually increased when amount of rainfall increased,the entrapment rate increased when the amount of rainfall diminished.

• Analysis on Precipitation Altostratus Microphysical Structure in Spring over North-East Qinghai
• ZHAO Shi-xiong;CHEN Wen-hui;HANG Hong-zong
• 2002 Vol. 21 (2): 281-287. 
• Abstract ( ) PDF (623KB) ( )
• Using the cloud particle spectrum data of precipitation altostratus by airplane observations in May and June 1977-1979 over north east Qinghai,the characteristic parameters of cloud group particles and microphysical structure statisticlly analysed.The vertical distributions of cloud drop concentration,water content,cloud drop average radius and maximum radius show that the coagulation water phase can be partitioned into 4 growth layers.There is a active growth layer over sea level about 5 km that may be an important feature layer to occur rain in altostratus there.In the meantime,the relationship of liquid water content with cloud temperature and with precipitation value are analysed.

• Numerical Simulation of Heterogeneous and Unsteady Transport and Diffusion of Line Seeding Sources within Stratus
• YU Xing;DAI Jin;GUO Jian-xia
• 2002 Vol. 21 (2): 288-295. 
• Abstract ( ) PDF (886KB) ( )
• Most transport and diffusion models usually use some questionable assumption,which can cause some important physical processes of transport and diffusion that is ignored.Puff trajectory model can deal with the temporal spatial variation of source parameters and meteorological elements,and can be used to simulate the diffusion of all kinds of scales and sources.Therefore,a 3-D puff trajectory model has been formulated to simulate the transports and diffusions of line seeding sources within stratus.Effects of topography and vertical wind shear,temporal spatial variations of seeding parameters and wet deposition are considered.The model results from a case study show that the general features of diffusion and transport are consistent with basic theory of diffusion,and represent the heterogeneity and unsteadiness of diffusion.Compared to diffusion of point source under homogeneous and steady condition,the horizontal and vertical concentration distributions are irregular,and more complex,Gaussian plume model can not longer be suitable for presenting them.In addition,the model can simulate the structures of line sources in detail.

• Characteristics of Ground Flashes in Hefei Region
• ZHU Bao-you;TAO Shan-chang;LIU Yi-feng
• 2002 Vol. 21 (2): 296-302. 
• Abstract ( ) PDF (1536KB) ( )
• Characteristics of return strokes in Hefei Area measured by a VLF/VHF radiation recording system is presented.The number of strokes per flash does not show a exponential decay distribution.However,flashes whose stroke number are below 5 to occur almost equally to each other and single stroke flashes account for about 15% of total flashes.The average number of strokes per flash is 4.2 and the maximum number ever measured is 16.Normalized(to 100 km) strength of return strokes distributes log normally.For 169 first return strokes the geometric mean of initial electric field peak normalized to 100 km is 9.3 V·m ^-1,the same value for 485 subsequent strokes is 4.5 V·m ^-1 and the most probable range is between 2 and 4 V·m ^-1.On a statistical base the subsequent stroke is weaker than the first stroke,while it is interesting to note that about 18% of ground flashes have at least one subsequent stroke whose initial peak is greater than the peak of the first stroke.The interstroke interval distributes log normally with the minimum value of about 1.6 ms.About 30% intervals are larger than 100 ms and intervals between 40 ms and 100 ms account for about 50%.The ratio of the field peak of two successive return strokes varies systematically with the time interval between them:Intervals less than 40 ms are dominated by the fact that the larger stroke occurs first,while about 55% of intervals more than 100 ms are featured by the preceding return stroke being weaker than the successive one.

• Circulation Dynamical Structure in Course of Dust Storm Occurrence in North China in Spring of 2001
• WANG Ke-li;JIANG Hao;WU Hong
• 2002 Vol. 21 (2): 303-308. 
• Abstract ( ) PDF (505KB) ( )
• The fields of geopotential height,vorticity,divergence and wind speed as the circulation dynamical structure in course of the dust storm occurrence in north China in spring of 2001 are analyzed based on the NCEP/NCAR data.The results show that there are some similar circulation dynamical structure features in strong stage of the dust storms.There is a deep low-pressure system over Mongolia and a well-developed high pressure ridge system over Ural,and a strong pressure gradient between the both.It is the dynamical source driving dust.The low-pressure system is supported by positive center of vorticity,the minus vorticity area around it and strong gradient zone between both.There is a verticalstructure with convergence at lower-level and divergence at upper-level in the center of system,it is favorable for occurring strong wind near ground and rising air stream which raise dust into the dust storm.The strong wind region is cosistent with the strong vorticity gradient zone.The vorticity transfer made by the strong wind shear strengthens the low-pressure system and then enhances the wind speed further.

• Preliminary Study on Surface Radiation Properties in Arid Region of Northwest China
• FAN Li-jun;WEI Zhi-gang;DONG Wen-jie;WEI Guo-an
• 2002 Vol. 21 (2): 309-314. 
• Abstract ( ) PDF (515KB) ( )
• The characteristics of diurnal variation of surface radiation in clear sky over Dunhuang,Desert and Zhangye were analysed and compared by using the short-period observational data of radiation balance at Dunhuang(Gobi) in June 2000,Desert and Zhangye(oasis) in June 1991.The results show that the daily-mean value of the transparency of atmosphere is 0.603 at Dunhuang and compared with Lasha,Naqu,Gaize and Ganzi,the transparency of atmosphere is very low.From the results,we can also see that,at three stations,the global radiation at oasis and desert is stronger than at Gobi;the surface albedo at Gobi and desert is higher than oasis;for the surface effective radiation,we find that the value at Gobi is the biggest,the next one is at desert,and the smallest one is at oasis;for surface net radiation,the value at oasis is higher than at desert and Gobi.

• A Local Nonlinear Dynamical and Statistical Climate Model and Its Forecasting Test
• CAO Jie;TAO Yun
• 2002 Vol. 21 (2): 315-321. 
• Abstract ( ) PDF (817KB) ( )
• After introducing the linear spline function,a local nonlinear dynamical and statistical climate model and its inversion method was designed according to the inversion theory.Studying the nonlinear evolution features of the local climate system with stepwise linear method is the essential of the model.As the primary examination,the local dynamical and statistical climate model was retrieved with the monthly temperature anomaly and rainfall anomaly ratio of 18 observatories of Yunnan provincefrom January 1956 to December 1990.The forecasting ability of this model was tested with the same time series but from January 1991 to December 1994.The fitting accuracy of temperature anomaly and rainfall anomaly ratio is 78% and 64% respectively.The forecasting accuracy of temperature anomaly and rainfall anomaly ratio is 75% and 63% respectively.These examination results indicated that this model has efficient fitting and forecasting ability,and has better stability.

• Time-Space Changing Character of Low-Level Wind in Lanzhou City and Its Correlation with Air Pollution
• LIU Yu;WANG Shi-gong;SHANG Ke-zheng;YANG De-bao;QI Bin
• 2002 Vol. 21 (2): 322-326. 
• Abstract ( ) PDF (552KB) ( )
• The ground wind speed and air pollutant concentration data monitored by Automatic Monitoring System of Lanzhou environment monitoring station during the period from 1988 to 1992,low level wind data in Lanzhou city and the ground wind data of urban and suburb distric of Lanzhou in latest 40 years were analyzed.We also contrast the urban district with the suburb monitoring point(Yuzhong station).The results reveal the regularities of wind direction distribution and the daily,annual and interannual variations of wind speed as well as the characteristics of wind changing with height.At the same time,the distribution of air pollutant conecntration and its correlation with wind speed in the parallelism period have been analysed.The results will provide the bases for investigating time space changing regularity of stability of boundary layer and develope air pollution forecast in Lanzhou city.

• Analyses of Cloudiness,Sunshine,Temperature and Daily Range on the Eastern Side of Qinghai-Xizang Plateau in Recent 40 Years
• LI Yue-qing
• 2002 Vol. 21 (2): 327-332. 
• Abstract ( ) PDF (369KB) ( )
• The variations and interrelations of the cloudiness,sunshine,temperature and daily range of the cooling region on the eastern side of Qinghai-Xizang Plateau are statistically analyzed during the last half century.It is obtained that the climate change has obviously regional characteristics on the eastern side of Qinghai-Xizang Plateau.The total cloudiness and sunshine have closer opposite relation than that of China.Both have well linear correlation with daily range and have closely correlation with temperature in spring and summer,but do not in autumn and winter.Finally,it is pointed out that the cloudiness and sunshine are possibly important reasons for the variation of temperature on the eastern side of Qinghai-Xizang Plateau in spring and summer.But in autumn and winter,the variation of temperature is connected with the general circulation in Asia and the influences of Qinghai-Xizang Plateau.

• Appl ication of Theory of Fuzzy Mathematics in City Environmental Noise Monitoring
• ZHANG Cun-jie
• 2002 Vol. 21 (2): 333-336. 
• Abstract ( ) PDF (294KB) ( )
• The relative cluster analysis of data about city network noise monitoring in 1990-1993 by theory of fuzziness were described in this paper.The environmental noise optimum places of Lanzhou city were made by calculating the closing degree and near point method.The unoptimized data in 1994 and 1995 were now optimized and checked in order to test the realibility of optimized data.The result shows that the city environmental noise monitoring in theory of fuzziness is feasible,accurate and successful.