【摘要】 本文应用了1951—1980年4—9月月平均和1961—1970年4—9月旬平均降水资料,研究了东亚、南亚和东南亚降水的年变化和年际变化,分析了中国东部、西部降水差异及长江流域夏季旱涝的特征.结果指出,东亚、南亚和东南亚4—9月200mm以上大雨区分布的总趋势呈西南-东北向,它和西南季风的走向近于一致.在这条大雨带之中,包括了三种不同类型的降水.此外,中国江淮地区旬降水量在7—9月存在周期约为20天左右的准周期振荡现象,它和中国西部的降水分布完全不同.中国华南和华中的降水与El Nino现象具有相反的关系.统计结果表明,长江中下游夏季发生持续性多雨和持续性少雨的机率只有23％,大部分年份属于正常降水年份.最后也讨论了影响长江中下游地区夏季旱涝的环流因素.更多还原

【Abstract】 The regional distribution of precipitation of more than 200 mm/month appears to be in the southwest-northeast direction that consists with the moved direction of the southwest monsoon in East Asia, Southeast Asia and South Asia during the months from April to September. In this large rainband, there are three different kinds of precipitation, i.e. the rainbancl of East Asia associated with seasonal variation of the general circulation in East Asia, the rainfall belt from the Bay of Bengal to Southeast Asia influenced mainly by the convergence of monsoon flows (ITCZ) and the dynamical role of topography, and the heavy rain belt in the west coast of India connected with the influences of southwest monsoon and topography.There are quasi-periodic oscillation of 10-day mean rainfall with quasiperiod of about 20 days in Central China from July to September. When the El Nino phenomena occur, the rainfall amount is rich in South China and poor in Central China. The relationship between El Nino phenomena and rainfall amount is opposite in South and Central China. But, it is uncertain in North China.The distribution of rainfall is very complex in West China because of the influences of Tibetan plateau. The amount of rainfall at stations located at the south of the plateau increases from April to August and decreases from August to September. The rainfall amount at stations located at the north slope and the moisture with southwest monsoon over these regions.According to the 30-year precipitation data of 1951-1980, the rate of rainfall of persistent heavy rain and persistent light rain is only 23% in the middle and low Yangtze River Valleys. Most of the 30 years are normal precipitation years. As to the factors that influence the flood and the drought in Yangtze River Valleys, southwest monsoon, crossing equator flows originated from Australia, subtropical high in West Pacific and cold air in Siberia and their interactions are cosiderable factors to mid-long range forecast of precipitation in Yangize River Valleys.更多还原