Current Issue

• THE PRECIPITATION CHARACTERISTICS OF MESOSCALE CONVECTIVE COMPLEXES OVER THE EASTERN REGION OF THE QINGHAI-XIZANG PLATEAU
• Zhong Xiaoping;Yang Shuqun;Zhu Yuanqun
• 1994 Vol. 13 (2): 113-121. 
• Abstract ( ) PDF (340KB) ( )
• The eastern region of the Qinghai-Xizang Plateau is one of frequent action area of mesoscale convective systems(MCSs) in China.The precipitation characteristics of one set of large MCSs, which appeared in July and August of 1984, 1985 and 1986, are analysed by using hourly precipitation data with a new definition slightly different from Maddox's. In this region, 30% to 50% of heavy rainfall(10 mm/h) is caused by MCCs. On average, MCCs produced a rain volume of 2 73 km ³ during their life cycle. Rainfall from MCCs have obvious diurnal variation with the time of maximum at 03LST and minimum at 17LST, 3 to 4 hours later than U.S. MCCs. During the life cycle, rain volume from MCC reaches the maximum at the intersection of the developing and the mature stages while the strongest rain intensity appears in late initialing stage and early developing stage. In the initialing stage, rain area coverage increases from a small proportion to about half of the cloud anvil, and almost keep the same percentage through the developing and the mature stages. Some remarkable diferences have been found between the MCCs formed in China and United States. The major rain area of the former is located in the front part with respect to the general direction of MCC movement. The proportion of rain area under the cloud anvil is much larger in Chinese MCCs than in U. S.MCCs. The property of transformation from convective to stratiformis precipitation during the MCC life cycle is even more obvious.

• 500 hPa TELECONNECTION PATTERN EXCITED BY THE SURFACE HEATING FIELD IN THE QINGHAI- XIZANG PLATEAU IN WINTER AND SUMMER
• Li Chao
• 1994 Vol. 13 (2): 122-127. 
• Abstract ( ) PDF (234KB) ( )
• In this paper, The thermodynamic influence of the Qinghai-Xizang Plateau is discussed based on the intensity of surface heating field in the Qinghai-Xizang Plateau and the correlation field between the intensity of surface heating field in the Qinghai-Xizang Plateau and 500 hPa gepopotential height field in winter(Feb.) and summer(July). According to the foregoing statistical discussion, it may be noted, the surface heating field in the Qinghai-Xizang Plateau in winter can excite the 500 hPa teleconnection pattern in the northern hemispheric atmosphere.The teleconnection pattern can be regarded as two-dimensional Rossby wave train and can propagate northeastward direction from low latitude to high latitude in northeastern direction. The surface heating field in the Qinghai-Xizang Plateau in summer can excite the teleconnection pattern in the northern hemispheric atmosphere.The teleconnection pattern is similar to EU teleconnection pattern, it can be regarded as two-dimensional Rossby wave train and can propagate northwestward direction from low latitude to high latitude.The propagation direction of the teleconnection pattern is opposite in winter and summer.This may be relate to the intensity of westly airstream in winter and in summer.

• EFFECT OF CLOUD ON THE SURFACE EFFECTIVE RADIATION OVER THE QINGHAI-XIZANG PLATEAUⅡ CLOUD RADIATIVE FORCING
• Wang Keli;Zhong Qiang
• 1994 Vol. 13 (2): 128-134. 
• Abstract ( ) PDF (251KB) ( )
• The calculating method of the surface longwave cloud forcing( CF) and the other related parameters is developed and the results are analysed based on the observed surface radiation data over the Qinghai-Xizang Plateau during the period from August 1982 to July 1983. The results show that diurnal amplitudes of the annual mean effective radiations for clear-sky F 0 and overcast F c as well as CF are related to geographic location remarkably. CF is larger in spring and summer and less in autumn and winter. The annual mean CF at Garzê, Lhasa, Nagqu and Gêrzê is -27 2 W/m ².

• THE OBSERVATION AND RESEARCH FOR THE CONTINENTAL AEROSOL BACKGROUND CHARACTERISTICS IN THE NORTHERN PART OF THE QINGHAI-XIZANG PLATEAU
• Yang Longyuan;Wang Mingxing;Lu Guotao;Gong Yanbang
• 1994 Vol. 13 (2): 135-143. 
• Abstract ( ) PDF (325KB) ( )
• It has been studied that the observation data of aerosol size distribution, elemental composition and different size stage characteristics which were sampled at Wudaoliang of the Qinghai-Xizang Plateau, in August 1989. The results point out that there is a "transitional peak" which is caused by the second fine particles number suddenly reduces and the peak lies in the 0 35 0 55 μm region in the aerosol size distribution curve. The special transitional peak maybe is the characteristic peak for the continental background aerosol size distribution curve. In this paper, it has been reported also that concentrations of 19 elements of aerosol composition and different size stage distribution data, which was measured at 2 different function sites of Wudaoliang, Qinghai Province. Where, S is 112 2 ng/m ³, Pb is 10 3 ng/m ³, respectively. The values are very lower and can compare with the value were measured at remote area such as Greenland Island and Arctic, etc..The elements different size stage distribution curve show as double model, quasi-smooth model and single model, and they represent the 3 aerosol sources at Wudaoliang: wind and sand dust, transportation dust and local pollution dust, respectively.

• SUMMARY OF THIRTY-FIVE CASES NUMERICAL WEATHER PREDICTION WITH A LIMITED AREA MODEL
• Qian Zhengan;Chen Yuchun;Li Suhua;Lu Shihua;Gu Hongdao;Li Lanping;Song Jie
• 1994 Vol. 13 (2): 144-152. 
• Abstract ( ) PDF (346KB) ( )
• To test the probability making the operational prediction with a limited area model under the operational environment and to test the performance of the model, in this paper a limited area model system suitable for complex terrain regions, with quite complex model physics processes, was used, a set of 48-h forecasting for 35 cases totally including both the periods of July 1 30, 1981 and August 10 14, 1988 was conducted utilizing the ECMWF's 2 5°×2 5°lon./lat. gridded data and the DCD code station data from National Meteorological Center of China, respectively. The paper is the summary of the prediction test verification. The objective and subjective verifications of both the circulation situation and precipitation predictions show, the model has already had the probability making the operational prediction under the operational environment and has a quite good performance as well, especially in heavy rain forecast.

• STUDIES OF DYNAMIC INFLUENCE OF QINGHAI-XIZANG PLATEAU ON THE MOVING EASTWARD TROUGH IN WINTER PART I. SOME ASPECTS OF STATISTICAL FACTS
• Jiao Yanjun;Qian Zhengan
• 1994 Vol. 13 (2): 153-161. 
• Abstract ( ) PDF (324KB) ( )
• In the first part of the series papers, utilizing daily historical synoptic chart data at 500 hPa level for 5 years in winter months (November to March), the statistics of frequency distribution, moving path, velocity and intensity of moving eastward trough over and around the Qinghai-Xizang Plateau (25°-60°N, 50°-120°E) are done objectively and quantitatively, so as to analysis the Plateau orographic influence on moving eastward trough. The results show:on an average, there are about 8 times moving eastward trough precesses a month in winter;Middle -Asia in the west side of the Plateau is the highest frequency area of the trough occurence;troughs of ten move eastward along the paths W, NW, S and N (especially the first two paths).Because of resisting and reducing effects of the Plateau, the troughs with paths W and NW (especially the former)often slow down, and decrease their intensity significantly, and even disappear, when they approach the west side of the Plateau;in contrast, while they move away the Plateau, all their intensity and velocity will increase in one way or another.When the troughs with Path S reach to the west side of the Plateau, they will be slowed down, the axes of troughs change their directions from N-S to NW-SE, and their intensity also reduces dramatically.

• THE GRID PROCESS OF SOIL-TEMPERATURE AND PRECIPITATION DATA AND SOME PRELIMINARY ANALYSIS RESULTS IN CHINA AND MONGOLIA
• Hu Zeyong
• 1994 Vol. 13 (2): 162-168. 
• Abstract ( ) PDF (250KB) ( )
• By using a stepwise searching approximation method, a data base of soil temperature and precipitation on grid point was gained. Based on these data, the percentages of same sign between soil temperature departure at depth of 1.6 m in winter (December to February) and precipitation anomalous percentages in following flood season (April to September) are calculated in China, at 100°E eastward and westward regions in China and Mongolia. The percentage of same sign reaches 54.5%, 53.8%, 55.6% and 51.4%, respectively.It is proved that there really exists a good positive correlation between soil temperature at depth of 1.6 m in winter and precipitation in following flood season. In general, this relationship is better in the west part of China than that in the east part of China, better in the south than that in the north.On the other hand, it is proved that the data on grid point could be compared with original data. The secular mean same sign percentages for soil temperature departure at depth of 1.6 m lead(lag) precipitation anomalous percentages in flood season by several seasons also are calculated.In general, when soil temperature lead precipitation, the percentages of same sign are more than 50%;otherwise, less than 50%. It shows that the soil temperature is indeed a pre-factor of precipitation, there is a maximum value when soil temperature lead precipitation in following flood season by 3 seasons. It shows that the positive correlation between the soil temperature at depth of 1.6 m and precipitation in following flood season is the best in autumn, not in winter.This results can improve the valid time of precipitaton forecasting in flood season.

• NUMERICAL SIMULATIONS OF EFFECTS OF LOCAL CLOUDINESS CHANGE ON CLIMATE
• Qian Yun;Qian Yongfu
• 1994 Vol. 13 (2): 169-177. 
• Abstract ( ) PDF (376KB) ( )
• A three-dimensional limited area model is used to simulate the effects of change of local cloud amount on climate. In the model, the real summer average cloud amount data in east hemisphere is used and the cloud-radiative computation scheme is improved. Results show that climatic effects caused by the change of the Plateau cloud amount and ITCZ cloud amount are mainly located in the Qinghai-Xizhang Plateau area. When the surface albedo is lower, the decrease of cloud amount in the Plateau area causes the land surface heated, pressure system enhanced both in the lower and the upper atmosphere. When the surface albedo is higher, the results are reversed. The decrease of ITCZ cloud amount causes weakening of the pressure system in the Plateau and cooling of the Plateau surface through the atmospheric circulation.

• SEASONAL MEAN SOIL TEMPERATURE ANOMALY FIELD AT DEPTH 3.2 m AND ITS APPLICATION IN PREDICTION FOR FLOOD SEASON
• Tang Maocang;Zhang Jian
• 1994 Vol. 13 (2): 178-187. 
• Abstract ( ) PDF (378KB) ( )
• All of the atmospheric vibrations with the time scale less than 10 years are only a little contribution to the amplitude of soil temperature at depth 3.2 m (about 0.05 0.15℃, except the normal annual cycle), due to that of the short period (such as diurnal cycle, natural synoptic period) or the small amplitude of air temperature (such as monthly、seasonal or interannual variation) So that the anomaly field of T 3.2 ( T'3.2) is almost like a indicator of thermal process in lithosphere, specially the high(low) value regions with the | T'3.2|≥ 0.5℃ are definitive indicator. After analysing the seasonal mean field of T'3.2 since 1980, it is found that the high value centers of T'3.2 have a regular evolution:the location of high center is almost steady during the initiate stage until the warmest stage, which is also the seisms active stage, hence the horizonal gradient of T'3.2 decreased and the center separated each other during the weakening stage. Whenever the horizontal scale of high temperature region reaches to 1 000 km in the warmest stage, the precipitation system in atmosphere will be aroused over the high temperature region, which will have more rain;if the scale less than 1 000 km, the precipitation system will not be aroused.

• A NUMERICAL SIMULATION OF THE MICROPHYSICAL PROCESSES OF FORMING HAIL OVER THE EAST QINGHAI-XIZANG PLATEAU
• Ma Lin;Zhao Shixiong;Zhang Guoqing
• 1994 Vol. 13 (2): 188-193. 
• Abstract ( ) PDF (223KB) ( )
• In this paper, the hail weather process under a westerly trough effect over the eastern Qinghai-Xizang Plateau is simulated by using one-dimensional half time-dependent two-parameterized model.The characteristics of dynamics and thermodynamics in the hail cloud, and producing and transition of supercooled cloud droplets, ice crystals, graupels and hails, the collection growing of precipitation particels are discussed and the mechanism of forming hail in the plateau hail cloud is also sought preliminarily.

• THE COMPARATIVE STUDY OF TWO OBJECTIVE ANALYSIS METHODS:SUCCESSIVE CORREC- TION AND OPTIMUM INTERPOLATION
• Su Zhixia;Cheng Linsheng
• 1994 Vol. 13 (2): 194-205. 
• Abstract ( ) PDF (528KB) ( )
• The contrast test has been performed in a regional objective analysis for the zonal and meridianal components of wind ( u and v), temperature ( T), relative humidity ( RH) and surface pressure ( P _s). In order to describe the meso-α scale atmospheric feature, when the successive correction scheme is used, the multiple weighting function, which are circle, elliptical and curved elliptical, is designed. The optimum interpolation scheme used univariate 2-dimensional correlation Ganssion function model. The results show that the two methods give very close results in areas of dense data network, and the results of the optimum interpolation scheme is better than the successive correction scheme in areas of sparse data network. Used two analysis solutions as initial fields of forecasting model, respectively, the results of forecast show that the 24h forecast using the successive correction scheme is better than using the optimum interpolation scheme, but the 48h forecast results are contrary to the 24h forecast results, but for all, the optimum interpolation scheme is better than the successive correction scheme in areas of sparse data network.

• THE RESPONSE OF TOTAL OZONE TO THE LONG-TERM VARIATION OF SOLAR ACTIVITY
• Wu Tongwen;Qu Zhang
• 1994 Vol. 13 (2): 206-211. 
• Abstract ( ) PDF (276KB) ( )
• Year-to-year mean total ozone at 10°, 20°, ……, 70°N from 1959 to 1985 have been analysed by methods of the maximum entropy spectrum analysis and regression analysis. The results show that the response of total ozone to 11- and 22-year periodic variation of solar activity is different at each latitude. At low and high latitudes, the response of total ozone to 22-year periodic variation is more intensive than that to 11-year periodic variation;at middle latitudes, especially 50°N, it is opposite, the response of total ozone to 11-year periodic variation is very distinct.

• THE RELATIONSHIP BETWEEN HEATING CONDITIONS OVER THE QINGHAI-XIZANG PLATEAU AND RAINFALL IN SPRING IN THE EASTERN PART OF QINGHAI PROVINCE
• Sun Wulin
• 1994 Vol. 13 (2): 212-216. 
• Abstract ( ) PDF (190KB) ( )
• In this paper, We chose indexes of OLR departure and air temperature departure to express heating conditions over the Qinghai-Xizang Plateau.They are close relating to the air circulation and Subtropical High.The correlation between the heating conditions over the Qinghai-Xizang Plateau and the rainfall next spring in the eastern part of Qinghai Province is studied.The four pridiction factor are gained and regression equations are set up.Tested result is very good in 1992.

• EFFECT OF CIRCULATION VARIATION ON PRECIPITATION IN MAY IN YUNNAN PROVINCE AND ITS LONG-RANGE FORECAST
• Yan Huasheng;Zhang Qing;You Weihong
• 1994 Vol. 13 (2): 217-223. 
• Abstract ( ) PDF (260KB) ( )
• The relationships between precipitation in May in Yunnan province and 100 hPa, 500 hPa geopotential height fields of the Northern Hemisphere from January to March are studied by using monthly mean data during 1956 1992. The effect of atmospheric circulation systems and the variation of main atmospheric active centres on drought/flood in May in Yunnan province, and wave train construction of teleconnection are studied. Based on the analysis of the circulation variation, a long-range forecast method is formed.