全球变化与亚洲季风

GLOBAL CHANGE AND ASIAN MONSOON

本文介绍近年来季风研究的某些进展，着重介绍和探讨青藏高原和ＥＮＳＯ事件对于中国和印度夏季风雨量变化的影响以及在全球变暖的背景下中国和印度季风雨量的可能变化。

Some progresses on the study of monsoon in recent years are introduced in this paper.The focal point is to study the impact of the Tibetan Plateau and the ENSO event on Chinese and indian Monsoon rainfall and its the possible change under the background of global warming.Before the 1980s, Chinese scientists held that monsoon is caused by the thermodynamic difference between solar radiations on continent and ocean in summer and winter, and the Tibetan Plateau functions as intensifying and stabilizing monsoon in the summer. For example, there was a closed high pressure centre in the temperature field on 500 hPa in July. The high centre is close to Lhasa (30°N, 90°E),with a little moving from year to year. The temperature at the centre is 6-10℃higher than south and north of it. This centre results from the famous thermal source of the Tibetan Plateau. The result of numerical simulation demonstrated that the thermal source of atmosphere above the Tibetan Plateau has a very important effect on forming and maintaining the monsoon circulation of East and South Asia.In the summer, the superposition of both solar radiation and the temperature difference between ocean and continent makes the temperature in the Arabian Peninsula 16℃ higher than that near the equator in the Indian Ocean. This is a basic reason for forming indian monsoon. The temperature gradient is not too large in the 0--20'N region of East Asia. But, north of 25°N, temperature gradient formed by solar radiation is opposite to the temperature gradient formed by temperature difference between ocean and continent, with both to cancel out each other. Therefore, the temperature difference between South and North China is not large in the summer, resulting in a prevailing South wind.Asian monsoon is a major factor in the atmosphere-ocean-Asian monsoon coupled system and also plays an important role in the global climate system.The ENSO event is a phenomenon due to the combination of E1 Nino and Southern Oscillation. It has an important effect on precipitation in india but no effect on precipitation in China. The reason is that the synoptic system of influencing Indian monsoon rainfall and other factors are relatively simple, while the system of influencing Chinese monsoon rainfall and others are more complicated.According to the above studies and our analysis on the potential change of Chinese monsoon rainfall under the background of global warming, there are two points worth to be stressed.(1) An opinion based on obviously global warming in the 1980s insists that global temperature will continue rising in the 1990s and the first half of the 21 st century. We think that this opinion is not enough proofs although we haven't enough reasons to prove that this continuous warming must be impossible. In the early 1970s, many Chinese and foreign scientists thought that a Little Ice Age would come with global cooling. In fact, however, rapidly global warming occurred in the 1980s. The failed forecast tells us that our knowledge on global climate change is not enough still. The author holds the study of global climate change not only should be carried out in the atmosphere but also should extend to all spheres of the Earth and other celestial bodies. This means that global climate change is related to geological processes and the activities of other celestial bodies including the Sun.(2) The main factors of forming Asian monsoon are the seasonal difference of temperature between Asian continent and oceans(Pacific Ocean and indian Ocean)and the thermlal effect of the Tibetan Plateau. These two factors are not obviouslychanged in a short timle. So it can be inferred that monsoon rainfall in China andIndia will not obviously reduce in the 1990s and the first half of the 21st century.Satallite cloud possible of more than last 10 years show that the cloud systemof forming precipitation in South and Central China are generally create in the east ofthe Tibetan Plateau and then moves to the east of the Chinese subtropics region to rain. Since the altitude, shape and locati