南海夏季风的低频特征

THE CHARACTERISTICS OF LOW FREQUENCY OSCILLATION OVER SOUTH CHINA SEA

关键词:  南海  夏季风  低频振荡

Key words:  South China sea  Summer monsoon  Low-frequency oscillation

摘要:

利用1975-1993年(其中1978年缺)的向外长波辐射(OLR)资料,分析了南海低频振荡的季节变化特征及其与南海夏季风建立和活动的关系。结果表明:南海低频振荡在夏季风期间比冬季风期间明显较强,南海夏季风一般在初夏第一个较强低频振荡的负值位相开始建立;南海夏季风期间低频振荡的环流实体是ITCZ的南北振荡和西太平洋高压西脊点的东西摆动,低频振荡与南海季风的活跃和中断(或减弱)密切相关;南海低频振荡与大气环流的季节变化相叠加,造成夏季风经历了第一个低频振荡的建立,到第二、三个振荡的加强,再到第四个振荡的减弱这种演变过程。

Abstract:

Using the OLR(outgoing longwave radiation) data during 1975- 1993 (except for 1978),the characteristics of interseasonal variation of Low frequency oscillation in South China Sea and its relation to the establishment and activity of summer monsoon, are investigated. It is found: (1)The strength of the oscillation is stronger during the summer monsoon period than that during the winter monsoon period. the establishment of summer monsoon is in the negative phase of the first strong oscillation; (2)Low-frequency oscillation closely relates to monsoons activeness and interruption(or weakness), the circulation objects of the oscillation during summer monsoon period are the eastward and westward swing of the subtropical high over west Pacific,and the southward and northward vibration of ITCZ; (3) the intraseasonal oscillation accompanied with seasonal variation makes the summer monsoon experience the evolution from establishment in the first oscillation, the strengthening in the second and the third oscillation and the weakening in the fourth oscillation.