我国南方初夏汛期和东亚夏季风环流

THE EARLY SUMMER FLOOD PERIODS OF SOUTHERN CHINA AND THE SUMMER MONSOON CIRCULATION OF EAST ASIA

主要根据低层夏季风热力学性质与流场演变特点深入讨论我国南方初夏汛期包括华南前汛期和长江中下游梅雨期同夏季风活动的联系，分析了东亚夏季风环流建立过程的阶段性和类型，指出汛期的开始与结束同夏季风前沿位置变动一致。我国夏季风从开始到发展鼎盛时期低纬大气环流的演变过程各年不完全相同，主要可归纳为４类，每类包括４个或３个不同阶段，从而可认识到东亚夏季风体系结构的非单一性，它可有４种结构模型，即仅是东南季风Ｐ的单气流型、强东南季风Ｐ与弱西南季风Ａ的双气流型、强东南季风Ｐ和弱西南季风Ｍ的双气流型、强东南季风Ｐ和强（或弱）西南季风Ｍ以及弱西南季风Ａ的３气流型。

Based on the thermodynamic charactristics of the summer monsoon and the change of the lower layer wind fields, the relation between the early summer flood periods of southern China,including the first flood period of South China and the plum rains period of the middle-lower reaches of Yantze River and the activities of the summer inonsoon is analysed. The establishment processes of the summer monsoon circulation of East Asia are investigated. It is shown that the beginning and ending of the flood periods are exactly in accordance with the arrival and leave of the fore boundary of the summer monsoon. The establishment processes of the monsoon circulation from the very beginning of the arrival of the monsoon to the period of great prosperity of development are not the same for each year. They can be classfied into four categories. Each category may have four or three stages. And then the structure of the summer monsoon regime of East Asia is not unitary. There exist four types of structure model of the monsoon regime of East Asia.