Current Issue

• Numerical Study on Air Pollution Concentration over Lanzhou Winter under Complex Terrain
• JIANG Jin-hua;PENG Xin-dong
• 2002 Vol. 21 (1): 1-7. 
• Abstract ( ) PDF (341KB) ( )
• In this study, concentration of air pollutant (SO ₂ and fume)during winter period without obvious weather event from 2 to 3 December 1994 over Lanzhou, a city of complex terrain, is simulated with a coupled, high-resolution atmosphere-diffuse modeling system.The meteorological conditions (wind and inverse temperature)prevailing during the period are analyzed based on simulation productsof the Regional Atmospheric Modeling system (RAMS).And the dispersion of the air pollutant (SO ₂ and fume)over Lanzhou is studied with the use of the Hybrid Particle and Concentration Transport package model (HYPACT).The impacts of wind and inverse temperature on pollutant concentration are analyzed based on the simulating results.The results show that the changes of wind and inverse temperature have obvious influence on pollutant concentration, and that the modeling systems are suitable for simulating atmospheric boundary layer and air pollutant concentration over Lanzhou.This proves the feasibility of using the modeling systems to predict air quality over Lanzhou City.

• The Influence of Siberian High on Large-Scale Climateover Continental Asia
• GONG Dao-yi;ZHU Jin-hong;WANG Shao-wu
• 2002 Vol. 21 (1): 8-14. 
• Abstract ( ) PDF (296KB) ( )
• Siberian High is a very important atmospheric circulation system in wintertime (from January to March). It influences the temperature and precipitation in mid-high Asia remarkably. Its variability was investigated for 79 years (from 1922 to 2000). The central pressure intensity which reflects the air mass over the Siberian High center was measured by the mean sea level pressure averaged over 70°~120°E, 40°~60°N. Strong weakening in the central pressure intensity has occurred in recent couples of decades. From 1922 to the middle 1970s, Siberian High intensity showed slight positive trends, but not significant. The striking weakening in recent 20 years are most remarkable. Linear trend for NCAR series is -1.78 hPa/10a from 1976 to 2000, for CRU data sets the trend is -2.15 hPa/10a from 1976 to 1995.There are also very strong coupling between Siberian High and the undersurface climate across Asian continent.Averaged temperature over 30°~140°E and 30°~70°N correlates to Siberian High at -0.58 for 78 winters from 1922 to 1999. For precipitation, the correlation is -0.44 during 1922 to 1998, both statistically significant above 99% confidence level. Siberian High, Arctic Oscillation, Eurasian Pattern and Southern Oscillation together can explain 72% and 26% variance in temperature and precipitation, respectively. The fraction solely related to the Siberian High is 24% and 9.8% in temperature and precipitation.

• Climatic Condition and Chinese History(Ⅱ): "Good (Bad) Climatic Condition" and "Peaceful(Trouble) Times" in Chinese History
• TANG Mao-cang;TANG Chi
• 2002 Vol. 21 (1): 15-19. 
• Abstract ( ) PDF (207KB) ( )
• In Chinese history, most of Peaceful Times appeared in Good Climatic Condition (GCC), inversely, most of Trouble Times is in Bad Climatic Condition (BCC). Partition always occurred in long Bad Climatic Condition. Base on the relationship of GCC(BCC) and Peaceful (Trouble) Times, all emperors could be divided into 4 classes, viz. virtuous, sage, mediocre and atrocious. The long GCC is a beginning of glorious over China in early of 21 century. However, it should be pay enough attention for disturbance of BCC.

• A Primary Study of the Relationship Between TBB Fields and Water Vapor Distribution over Qinghai-Xizang Plateau in Summer
• JIANG Ji-xi;FAN Mei-zhu
• 2002 Vol. 21 (1): 20-24. 
• Abstract ( ) PDF (261KB) ( )
• Based on the contrast analysis of monthly GMS TBB and humidity ( T- T _d, θ _se)from HLAFS in summer 1998 over the Plateau and its surrounding areas, it is shown that the cloud field and cloudless field revealed by TBBshow directly the distribution of wet and dry air fields, and the low TBB bands orientated quasi-latitudinal and longitudinal patterns indicate vapor converging area and transporting channel, respectively. Therefore, some opinions, according to the analysis of mean TBBfields the summer of the 17 years were presented that the air is drier over the northern Plateau and very wet over the southern Plateau where wetter area is in middle and eastern regions and two wet centers embedded in it and drier in western regions;the water vapor source over the Plateau comes from the Bay of Bangal and Arabic Sea and its entrance into the Plateau is in the some favorable regions between 85°~95°E.

• Daily Variation of Heat Sources over the Eastern Qinghai-Xizang Plateau and Surrounding Areas and Their Relationship to the Circulation over the Tibetan Plateau
• JIAN Mao-qiu;LUO Hui-bang
• 2002 Vol. 21 (1): 25-30. 
• Abstract ( ) PDF (300KB) ( )
• Using the twice daily routine rawinsonde data in the domain 90°~130°E, -5°~45°N from 1 May to 31 August 1998, the heat source and moisture sink are computed, and the diurnal variation characteristics of heat sources and moisture sinks and their relationship to the circulation over the eastern Qinghai-Xizang Plateau are analyzed. The results show that the heat sources over thearea from Indo-China peninsula to the eastern Plateau are stronger at 12:00 than at 00:00, while the heat sources over the area from the central South China Sea to the central China are strong at 00:00, but weak at 12:00. The moisture sink has a similar diurnal variation to the heat source. The ascending motion over the eastern Qinghai-Xizang Plateau becomes stronger significantly in the evening and the local meridional monsoon circulation also intensifies. Meanwhile, the ascending motion over the middle reaches of Yangtze river at 00:00 becomes weaker and turns to descending motion in the evening. Thus a local thermal diurnal zonal circulation exists with the up branch over the eastern Plateau and the down branch over the middle reaches of Yangtze river. The heavy rainfall in summer, leading to a flooding disaster, occurmainly early in the morning.

• Assessment of DDA for Computing the Backscattering by Oblate Spheroidal Particles with Experimental Data
• XU Xiao-yong;WANG Zhen-hui;WANG Qing-an;CHAO Zeng-ming
• 2002 Vol. 21 (1): 31-36. 
• Abstract ( ) PDF (247KB) ( )
• The discrete-dipole approximation(DDA) is an important theoretical method for computing scattering and absorption of electromagnetic energy by a particle of arbitrary shape. DDA for scattering calculations, including its validity criteria is briefly presented in this paper. The backscattering cross-sections of liquid and ice oblate spheroids incidented by polarized waves which are propagating vertically to their rotation axis, are calculated by DDA. The theoretical results are compared with the experiment data obtained with a microwave measuring system. It is shown that the theoretical results are consistent with the experiment data in general. As a result, the reliability of theoretical result is proved. Theoretical and experimental analyses indicate that the backscattering ability of raindrops and ice particles presents a curved change as the particle size increases, and fluctuates in the so-called resonance region. It is clear that the computation accuracy of DDA depends mainly on the number N of dipoles or the value of the | m| kd. In this article, the technique for the experiment to measure the scattering of simulated raindrop and ice particle is also described.

• Observational Research on Physical Feature of Summer Rain Dropsize Distribution under Synoptic Systems in Ningxia
• NIU Sheng-jie;AN Xia-lan;SAN Jian-ren
• 2002 Vol. 21 (1): 37-44. 
• Abstract ( ) PDF (320KB) ( )
• Rain drop size distribution(RDSD) have been measured at 7 meteorological stations in Ningxia during June to September from 1982 to 1984. 46 precipitation processes are observed and 6053 cases of RDSD were obtained. The features of RDSD and its physical parameters are analyzed combining general circulation patterns and synoptic systems. The mean space concentration of rain drop are 285 m ^-3, and mean RDSD can be written as N( D_i)=209.2exp(-2.6335 D_i). The relationship between radar reflectivity and rainfall intensity, rainfall kinetic momentum flux, rainwater content is established respectively. The relations can be used in rainfall and area rainfall prediction by radar quantitatively.

• Feature Analysis of Summer Water Resource in North China and Its Response to Climate Change(Ⅱ): The Relationship between Plentiful or Short of Summer Water Resource in North China and Climate Change
• FAN Guang-zhou;LüShi-hua;CHENG Guo-dong
• 2002 Vol. 21 (1): 45-51. 
• Abstract ( ) PDF (275KB) ( )
• Using the 40-year reanalysis data of NCEP/NCAR, we simply analyze the influence of the summer temperature and (or) precipitation on the summer water resource in North China. The result shows that there is a better relationship between the plentiful or short of the summer water resource in North China and the temperature and precipitation. We also establish the simple statistical evaluation model about the influence of the temperature and (or) the precipitation on the variables of the water resource. Using these models, we studied the response of the variables of the water resourcein North China to the different climate change. And we conclude some significative results.

• Variation Features of Winter Soil Temperature Field in the Depth of 3.2 m and Its Relation to Summer Precipitation Field in China
• ZHAO Hong-yan;LI Dong-liang;GUO Wei-dong
• 2002 Vol. 21 (1): 52-58. 
• Abstract ( ) PDF (284KB) ( )
• With EOF and REOF analyse techniqne, the spatial anomalous features and time evolution rule and the relation between winter soil temperature and summer precipitation anomaly in China are studied using soil temperature date in the depth of 3.2 m in December, January and February of 1980-1997 in 141 stations and the precipitation date in June, July and August of 1951-1997 in 160 stations.The results show that before rotating the first three loading vector fields can reflect the whole anomaly pattern structures of soil temperature in China, i.e., the higher (or lower) soil temperatures in whole calculated area, higher (or lower) ones in east-west direction, higher (or lower) ones in north-south direction. After rotating, the first four rotated loading vector fields represent four principal soil temperature anomaly patterns: i.e., North China, Huaihe river, Northwest China and of Yangtze river to the south. The rotated principal components and some station data show that there is an increasing trend of soil temperature in patters like North China, Huaihe river and Yangtze river to the south from 1990s, but vice versa for Northwest and South China patterns. When winter soil temperature of North China is higher, the July precipitation in most part of North China is obviously increased;when winter soil temperature of Huaihe river is higher, the July precipitation in both the Yangtze and Huaihe rivers is obviously increased and vice versa for Yellow river to the North and South China;When winter soil temperature of Northwest China is higher, the July precipitation in both the Yangtze and Huaihe rivers is obviously decreased;when winter soil temperature of South China, the July precipitation in Sichuan and north Yunnan is obviously increased.

• Climate Change and Its Impact on Desertization around Qinghai Lake
• LI Ling;WANG Zheng yu;QIN Ning-sheng;WANG Qing-chun
• 2002 Vol. 21 (1): 59-65. 
• Abstract ( ) PDF (268KB) ( )
• The climatic variation tendencies and jump phenomena of air temperature, precipitation, evaporation and etc around Qinghai Lake since 1976 are analyzed and verified. The result shows that the four seasons and the annual mean precipitation and air temperature are increasing. Among them, this tendency is more significant in autumn and winter. The annual mean precipitation and precipitation in spring, summer and winter have been decreased since 90s, especially, in the autumn, its linearity variation rate is -7.28 mm/10a;each season and annual evaporation appear to increase, its linearity variation rate of year and summer is 11.7 and 9.39 mm/a respectively. Each season and annual air temperature had a significant warming phenomenon. Although precipitation had a significant increasing and decreasing phenomena, but its increasing was in 1980s, and the decreasing was in 1990s;meanwhile, the evaporation also had a significant increasing and decreasing phenomena, its decreasing was in 1980s while its increasing was in 1990s. When the climatic tendency and jump are happening, it increase desertization expanding around Qinghai Lake, causes grassland degeneration, river flow decreasing and lake level descent;that is, it has a severe impact on ecological environment.

• Analyses on Interdecadal Change Characteristics of Global Winter and Summer Sea Surface Pressure Field and 500 hPa Height Field in Recent Twenty Years
• ZENG Hong-ling;GAO Xin-quan;DAI Xin-gang
• 2002 Vol. 21 (1): 66-73. 
• Abstract ( ) PDF (359KB) ( )
• The change characteristics of global monthly mean surface pressure field and 500 hPa height field in winter and summer before and after the abrupt change of climate in late 1970s were analyzed. The results indicate that the interdecadal abrupt change of climate is significant and global. Comparing after and before the abrupt change, it found that Aleutian low strengthens, with obvious east-moving in winter. Meanwhile East Asian major trough weakens and there is obvious systematically east-moveing too. The north of Siberian high becomes weak and the south of it strengthens in winter. Indian low and monsoon low of East Asia have the obvious weakness in summer and subtropical high system generally strengthens.

• Detecting and Processing Waveform from C-G and Cloud Lighting Discharge and It's Preliminary Application
• WANG Huai-bin;QIE Xiu-shu;ZHANG Yi-jun;ZHANG Cui-hua
• 2002 Vol. 21 (1): 74-78. 
• Abstract ( ) PDF (210KB) ( )
• A LLP made Direction Finder (DF) was connected properly with type TCCJ-2000 transient converter to record the strength and wave shape of the electromagnetic radiation from lightning flash with sampling time, recording length and bandwidth of 0.1 μs,204.8 μs and 500Hz~500kHz, respectively. Data collected were processed and stored by a PC through an installed inside PET-48DIO board. In addition, a preliminary data analysis was provided.

• A Study of Retrieving Aerosol Optical Depths from Direct Solar Irradiation
• DU Ping;QIAN Zeyu;CHEN Changhe
• 2002 Vol. 21 (1): 79-84. 
• Abstract ( ) PDF (312KB) ( )
• Two kinds of methods are used to calculate the aerosol optical depths of wide-band from the direct solar irradiation detected by pyrheliometer on the ground under the condition of cloud free sky. The results are obtained to be similar. The analyses of two methods show that the first method is conciser, while the equation used in it is curt, the second one is to definite the opximum wavelength, and the optical depth of the wavelength is regarded as the wide-band aerosol optical depth. So, the latter one is more precise on the theory, and more information can be obtained from the result. In a word, the latter is more resonable than the former.

• The Influence of Local Factor on Surface Layer Ground Temperature in Qinghai-Xizang Plateau
• WANG Shao-ling;DING Yong-jian;ZHAO Lin;Toshio Koike
• 2002 Vol. 21 (1): 85-89. 
• Abstract ( ) PDF (201KB) ( )
• The influence of vegetation, snow cover, slope, lithological character, water content and building materials on surface layer ground temperature were discussed. The results show that the ground temperature in the areas with scattered vegetation is higher than that in uncovered land;A thin snow cover existed in a short period takes the role of lowering the ground temperature;the ground temperature in south slope are 2~7℃ higher than that in north slope;the ground temperature are directly influenced by the water content of soil;and the mean annual ground temperature on asphalt grounded surface are 4.5℃ higher than that on natural ground surface with crushed stone soils, and also higher than that on all pavement with other materials.

• Features of Photosynthetic Active Radiation(PAR) in Haibei Alpine Meadow Area of Qilian Mountain during Plant Growing Period
• LI Yingnian;ZHOU Huakun
• 2002 Vol. 21 (1): 90-95. 
• Abstract ( ) PDF (330KB) ( )
• The daily and seasonal variation features of PAR in alpine meadow area during plant growing period in 1998 were analyzed, the results show that the tendency of daily variation of PAR conformed with that of the solar global radiation presenting a single peak type. The maximum daily tolal PAR may amount to 11.7 MJ·m ^-2. The seasonal variation of PAR in the plant growing period (form the last ten days of April to the second ten days of September) is more complicated. The higher value of PAR appear before raining season and the lower value in other time. The maximum dekad mean value of PAR may amount to 85.23 MJ·m ^-2. The daily average variation of PAR/ E _gis from 0.36to 0.41. The seasonal variation of dekad mean PAR/ E _g is from 0.32 to 0.43. PAR can be estimated by the variation of E _gbecause of the positive correlation between PAR and E _g. The efficiency of energy conversion of PAR is 0.58% more or less in plant community of Haibei alpine meadow area.

• The Use of Neutal Network in Optimum Method of Original Meteorological Data
• CAO Xiao-zhong;WANG Qiang
• 2002 Vol. 21 (1): 96-101. 
• Abstract ( ) PDF (230KB) ( )
• Based on the deep research of neural networks and time series, the two methods are studied within a unified framework of system theory. Three optimum methods are proposed based on space, time, mode relativity using improved BP. The experiments reveal that the proposed methods are very effective in processing of data in HEIFE area.

• The Singular Value Decomposition Method to Prediction Experiment of Rainfall
• ZHANG Wan-cheng;XIE Ming-en
• 2002 Vol. 21 (1): 102-107. 
• Abstract ( ) PDF (242KB) ( )
• By using the singular value decomposition method, the SST and rainfall of May in Yunnan are analyzed. The physical signification of the correlation factors selected is clear. The method and multiple regressive are applied to prediction experiment of short-range climate, in the view of experiment result in six year experiments and two year single use, the method is more prediction capacity than multiple regressive model.

• Analyses on Climatic Features of Drought/Flood in Middle Reaches of Yarlung River
• HUANG Xiao-qing;HU Chu-yang
• 2002 Vol. 21 (1): 108-112. 
• Abstract ( ) PDF (203KB) ( )
• The monthly rainfall data of May to August of 4 stations in middle reaches of Yarlung river during 1960 to 1998 are used, the climate features of early summer and midsummer drought/flood are analyzed. The results show that the frequency of early summer drought is more than that of flood, but the probability of heavy flood is more than that of heavy drought. In midsummer, the frequency of flood is more than drought.The distribution of drought/flood is not uniform in 1960s and 1990s, there are more early summer flood and more midsummer drought during 1970s;the more early summer and midsummer drought in 1980s.The main oscillation periods of drought/flood in early summer are 19.5 and 2~3 years;but those in midsummer are 3~4 years.