Current Issue

• THE CLIMATIC AND SYNOPTICAL STUDY ABOUT THE RELATION BETWEEN THE QINGHAI-XIZANG HIGH PRESSURE ON THE 100MB SURFACE AND THE FLOOD AND DROUGHT IN EAST CHINA IN SUMMER
• Luo Siwei;Qian Zhengan;Wang Qianqian
• 1982 Vol. 1 (2): 1-10. 
• Abstract ( ) PDF (753KB) ( )
• According to the analysis of 13 years data, it is shown that there a re close relations bet ween the ridge and center positions of Qinghai-Xizang high pressure on lOOmb surface and the large scale distribution of floods and droughts in East China in summer. 1 The ridge position of Qinghai-Xizang high pressure on lOOmb surface, especially at 120°E, is closely related with the periods of Mei-yü and middle summer drought. In the period of Mei-yü the ridge position at 120°E is located in the 26°-32°N and in north of 33°N while in the period of middle summer drought. 2 The center of Qinghai-Xizang high pressure always occurs over the Plateau. It may be related to the heatimg effect of the Plateau in summer. The center and ridge positions of Qinghai-Xizang high pressure on 100 mb surface and the direction of ridge at 90°-120°E are also closely related to the drought and flood in East China. 3 There are three cirulation patterns i.e. east pattern, west pattern and zonal (transitional) pattern. In the periods of east and zonal circulation patterns the droughts occur at the middle and lower reaches of the Yangtze River, East Sichuan and Guizhou provinces and the floods occur at the West Sichuan and North China. On the contrary, the west circulation pattern brings rainy weather to the middle and lower reaches of Yangtze River, East Sichuan and Guizhou provinces, resulting in floods, but no raining weather (drought) occurs at the West Sichuan province.

• THE QUASI-THREE YEAR PERIOD OF PRECI-PITATION IN THE WEST OF OHINA
• Xu Guochang;Dong Anxiang
• 1982 Vol. 1 (2): 11-17. 
• Abstract ( ) PDF (459KB) ( )
• In this paper, using the precipitation data of 70 stations in the west of China, we have calculated the precipitation periods by the methods of periodogram analysis and power spectrum. It is found that the prevailing period is the quasi-three year period that appears mainly。to the north of 350°N,i.e. to the north of Qinghai-Xizang Plateau, and it is most apparent on the Plateau's northeast.The puasi-three year period of precipitation appears principally in spring and summer. From 1930s to 1970s, the quasi-three year period of the precipitation is relatively stationary. Its formation may be associated with quasi-three year latitudinal oscillation of the ridge line of southern Asia.In addition, there is a minor period of precipitation in the west of China, i.e. the ten to thirteen year period.

• A THERMODYNAMIC-STATISTICAL MODEL FOR THE LONG-RANGE RAINFALL FORECASTING AT THE FLOOD SEASON IN CHINA
• Wu Shijie;Tang Maocang;Zhong Qiang
• 1982 Vol. 1 (2): 18-24. 
• Abstract ( ) PDF (451KB) ( )
• In this model, three kinds of factors affecting the rainfall have been treated with various methods: the thermal terms of the underlying surface are solved by mathematical physics method; the advective terms are substituted by sea surface temperature of NW Pacific and the Tibet Plateau surface temperature, those can indicate the intensity of SE monsoon and Plateau monsoon, which are the prevailing system controlling the East Asia at the flood seasons the terms containing the surface albedo and soil humidity are treated with statistical method and an equation with the relationship between these elements and the rainfall amount is then obtained . The coefficients in this model are determined by a physics-statistical method.By using this model to predict the rainfall departure sign, its accuracy is 63% in the flood season of 1980.

• THE STRUCTURE AND PROPERTIES OF MEI-YÜ CYCLONE
• Yang Jinxi
• 1982 Vol. 1 (2): 25-36. 
• Abstract ( ) PDF (799KB) ( )
• In this paper a filter-compositing method is used to determine the average structure and properties of four medium-scale wave disturbances observed during the period in mei-yü season. The conclusions are given as follows: 1 .Mei-yü cyclone was most intense at 850mb, being cold core below and warm core above that level. It was a mid-low level and medium-scae wave disturbance and disappeared above 500mb. 2 .There were a maximum upward motion and a moisture saturation throughout the troposphere in mei-yü cyclone center,and its circumference. 3.A maximum moisture flux convergence was found in the center and south of 850mb cyclone. This was aJso the region of the largest precipitation. 4. Well-developed mei-yü cyclone had two vertical circulations, one being at the south side and other at the north side. 5.Generation and development of mei-yü cyclone was connected with gravitational wave instable development.

• A ANALYSIS OF UPPER WIND FLUCTUATION OVER EASTERN QING-ZANG (Tibetan) PLATEAU DURING EARLY SUMMER
• Liu Fuming;Tong Wenlin;Chen Xiaomeng
• 1982 Vol. 1 (2): 37-42. 
• Abstract ( ) PDF (461KB) ( )
• The characteristics of airflow in mid-lower troposphere during early summer between the Plateau monsoon active year (1967) and weak year (1969) are contrasted by using the upper wind data of Gan-Zi over eastern Qing-Zang Plateau. The features of wind fluctuation both in the Plateau monsoon level and Planetasy wind level are analysed, and the relations between these features and the precipitation over Sichuan basin droght region during early summer are also described. The spectral analysis of zonal and meridional wind components at 4,000m and 6,000m suggests that there exist 2-3 day and 5-6 day periods within the Plateau monsoon level and the peak of 10-day period exists in the spectral of zonal wind component at 4,000m during monsoon active year. There is only a 5-6 day period for the weak monsoon year and the 10-day period oscillation is prominent for the active monsoon year in the planetary wind level. Finally, the synoptic meaning is discussed.

• THE CHARACTERISTICS OF HAILSTORMS AND THEIR IDENTIFICATION WITH RADAR
• Gong Naihu;Cai Qiming
• 1982 Vol. 1 (2): 43-52. 
• Abstract ( ) PDF (736KB) ( )
• The data of 153 thunderstorms obtained during 1972-1976 with a 3cm werther radar at the Pingliang region have been analysed. The results show that there are remarkable differences between hailstorms and ordinary thunderstorms in their radar characteristics.If thunderstorms center refle-ctivities with respective echo heights. η= 10 ^-8 cm ^-1 and η=10 ^-7 cm ^-1 are adopted as criteria for identifying hailstorms, the accuracy rate might reach 88%.The vertical reflectivity profiles in the center of hailstorms are both larger (η>10 ^-8 cm ^-1) in its lower and middle parts (up to 6-9 km) , that is, the regions of reflectivity extend much thicker and higher, the PPI echo areas of η≥10 ^-7 cm ^-1 of the hailstorms at low angle of elevation are larger than 6 km ² as well.The more intense the hailstorms are,the more evident are these characteristics. Before a hailfall, the intense echo top appears in a vigorous growing state and the time necessary for its growth is generally not longer than 30 min, Afterwards, the hailstorms are in a quasi-stable period and keep the basic conditions for forming hails.

• THE LIGHTNING FLASH RATE CHARCTERISTICS OF HAILOUD AND THEIR APPLIGNTION IN HAIL SUPPRESSION
• Ye Zongxiu;Chen Qian;Guo Changming;Xia Yuren
• 1982 Vol. 1 (2): 53-59. 
• Abstract ( ) PDF (1417KB) ( )
• The characteristics of lightning flash rate of hailclouds are summarized, which were observed during 1976 to 1979 in Piugliang, Gansu, with a double channel. lightning counter. It is found that the flash rate depends on precipitation property (hail or rain) and is much higher in hailcloud than in thunderstorm cloud. A simple and practical index that the flash number during 5 minutes is more of less than 100 can be used to judge whether or not there are hailouds.within 40km from the observation site. The forecast accuracy is above 80% and the wrong and missing Irate are 9.4% arid 11.1%, respectively. A comparison is made between time variation of flash rate and that .of intensive radar echo (36dbz) height. It is found that there is apparently a positive correlation between them and that the time when hailcloud is identified both by radar index and by that of lightning counter is nearly, the same, This suggests that under certain circumstances the extent of lightning activity could be used to characterize the intensity of thunderstorm, and which can be seen from the. f act that when clouds are merging, the vigorous development of the merging Clouds is always followed by an abrupt flash rate increase. The reason why flash rate is Higher in hailcloud is discussed and some points are presented. which should be noticed in using a lightning counter.

• THE GRAPHIC ANALYSIS OF THUNDERSTORM CLOUD TOP LEVEL AND ITS CALIBRATON IN PRACTICAL FORECAST
• Zhang Xixuan;Ma Jide;Liu Yongping;Li Xiangdong
• 1982 Vol. 1 (2): 60-68. 
• Abstract ( ) PDF (574KB) ( )
• Willi the viewpoint concerning energy, and through the computation and analysis to the radar observed data of 68 times of thunderstorm cloud at the Pingliang district, of Gansu Province in the summers from 1973 to 1977 and their corresponding sounding data, we have discovered that the appearing of maximum cloud top level at that every day during the most intensive developing of thunderstorm follows a general rule. That is, when the middle layer(700-400mb) of atmosphere is circumstanced under a moderate dry or wet condition(th average relative humidity being 32-62%), the computed cloud top level almost coincides entirely with the level by radar sounding. This probability may approach 71%. When the stratified water vapour stands under a rather wet orrather dry condition. the observed cloud top level deviates from that by sounding. This generation of deviation has a close relationship with the conditions of water vapour. Hence, in focecasting the level of thunderstorm cloud top, on may,according to the T-lnp chart,use a method to compute the cloud top level first and then make some empirical calibration according to the conditions of water vapour.This method has been tried in practical forecast and also examined with the radar sounding. It proves that the two results are quite agreed with each other.

• OBSERVATION OF SOLAR RADIATION AND ITS CHANGES, DURING A SOLAR ECLIPSE
• Ji Guoliang;Chen Youyu
• 1982 Vol. 1 (2): 69-77. 
• Abstract ( ) PDF (609KB) ( )
• In the paper, the data of the solar radiation components observed during partial solar eclipse on July 31, 1981 is analysed. The results of analysis show: 1 In the partial solar eclipse, solar short wave radiation is rapidly weakened with increase of sun's surface covered by moon's umbra. Weakening of solar ultraviolet radiation is linearly decreased with, that of solar direct radiation. Long wave radiation is slightly weakened and its. mini-mum appears slightly later(about 10 minutes)after the middle of eclipse.In the partial solar eclipse, the values of terrestrial radiation balance (net radiation) pass the zero point twice, this variational process is similar to their daily variational process. In the partial solar eclipse, the maximum of the air temperature decrease is about 2.5°c and which appears after the middle of eclipse, too. 2 From the beginning to the end of eclipse (160 minutes), the net energy reaching the ground may lose about 59.2 cal cm ^-2. If we consider the area within the longitude 60°E and 160E and in the north of latitude 50°N, the total energy in this whole area may lose 4.8×10 ¹⁸cal, during the solar eclipse. In addition, the physical mechanism of the solar radiation components weakening in the partial solar eclipse is also briefly discussed.