EI Nino现象对东亚夏季风环流影响的初步研究

A PRELIMINARY STUDY ON EL NINO PHENOMENON AND THE INFLUENCE OF IT ON THE SUMMER MONSOON CIRCULATION OVER EAST ASIA

摘要:

本文分析了1971—80年发生在南美洲西海岸的EI Nino现象及其对东亚夏季风环流的影响。结果表明,1972和1976年为强的EI Nino年,而1971和1974年为显著的反EI Nino年。还指出,1—6月份南美西海岸的海温与7月份我国东部大部分地区夏季风呈负相关.在EI Nino年,主要环流的特征为:(1)西太平洋副热带高压脊线偏北,强度偏弱.(2)澳大利亚高压位置偏南。(3)赤道缓冲脊强大.ITCZ东伸到太平洋中部。南半球的信风在105°E附近越过赤道之后,于10°N折向东去,流入西太平洋.(4)印度次大陆季风中断.孟湾西南季风直接影响我国东部地区的分量极其有限,在反EI Nino年,上述各系统特征完全相反.我们认为,EI Nino现象的发生,引起夏季风环流系统的变动,最终影响到我国夏季风的强度,这是二者之间遥相关的一种可能过程.

Abstract:

In this paper, El Nino phenomenon occurred along the western coast of South America (1971-80) and the influence of it on the summer monsoon circulation over East Asia were analysed. The results show that the major El Nino years were in the years 1972 and 1976, while the pronounced anti -El Nino years were in 1971 and 1974. It is also pointed out that there was a negative correlation between El Nino and the summer monsoon over most part of East China in July.The major circulation characteristics in El Nino years are as follows; (1)The position of the western Pacific subtropical high lies to the north of its normal position and its intensity is week. (2)The position of the Australia high lies rather in south. (3) The equatorial buffer ridge is strong. The northern ITCZ extends eastward to the middle of the Pacific. After the south hemispheric trade crosses the equator near 105° E,it will turn eastward near 10°N and run onto the western Pacific.(4)The monsoon breaks over India subcontinent.The SW monsoon component from the Bay of Bengal which affects directly the east areas of China is very limited. The characteristics of each system as mentioned above in anti- El Nino years are quite different from that is El Nino years.When El Nino phenomenon took place, it results in the fluctuation of the summer monsoon circulation system,and at last exerts an influence on the intensity of the summer monsoon over East China. It is thought that this is a possible process of the teleconnexion between the El Nino, phenomenon and the summer monsoon.