东亚季风强弱变化及其对初夏我国东部地区降水的影响

THE VARIATION OF SUMMER MONSOON SYSTEMS AND ITS EFFECT ON THE PRECIPITATION IN THE EARLY SUMMER IN EAST CHINA

本文通过对东亚季风系统的分析,发现东亚季风存在3—4年左右的长期振荡。这类振荡与赤道东太平洋海面温度变化有相互作用,形成一个相互反馈的耦合振荡过程。据此提出海温通过季风系统的变化影响初夏我国东部地区降水分布的可能长期天气过程。

In this paper, the rainfall data in the late 30 years in East China is analysed. It is found that the variation trend of precipitation between North and South China is marked contrary in the early summer.The trend of North China is above normal in 50's, below normal from 60's to 70's, and with an opposite tendency in the South of Changjiang Valley.By analysing the variation of the sunner monsoon systems in East Asia, a long period of oscillation about 3 to 4 years is also obtained.The interaction between the monsoon oscillation and the variation of sea surfare temperature in east equatorial pacific produce a. feedback couple oscillation.According to the above results, a possible long range weather process model of the sea surface temperature effect on the rainfall distribution in East China through the variation of the summer monsoon systems has been proposed as follows.When the sea surface temperature in East equatorial pacific is higher that normal, the sea surface pressure in the easi equatorial Pacific is lower and the Australian anticycle is stronger, while the walker cell is weakened, the cross equatorial air currents and subtropical anticylones are also strengthened. So the summer monsoon circulation and the middle latitude westerlies in the East Asia are intensified.The precipitation is above normal in North China and below in South China. On the contrary, when the sea surface temperature in east equatorial pacific is cold, the walker cell is intensified and other monsoon systems are all weakened .Then the rainfall is below normal in North China and above normal in South China.