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本文利用经验正交函数分析了1981、1982年夏季,30°N—30°S、70°—150°E范围内气压场、云场中期变化特征。结果指出,东南亚夏季季风期内,气压场存在6—9天、2周、4—6周三种主要中期振荡。与此对应,地面气压场表现为三种典型的特征向量场分布形势,其中第一特征向量场代表季风环流形成,维持基本气压配置形势;第二、第三特征向量则是叠加在基本场上的扰动气压场,这是导致季风爆发、中断的气压场配置形势。上述三种类型可以反应出原场的60％以上的总信息量。 云场分析表明,季风期内云量场也存在三种主要形式,其一为东北—西南部云量变化符号相反;其二为东、西部之间及南、北部之间云量的相反变化趋势,这些变化特征是季风强,弱及在东西或南北之间进退的反应。 天气分析证实,上述变化往往从南部开始。因此,这一结果对我国夏季热带天气预报及降水中期预报有参考意义。
In this paper, the empirical orthogonal function is used to analyze the mid-term variations of the pressure field and cloud field in the summer of 1981, 1982, 30 ° N-30 ° S, 70 ° -150 ° E. The results indicate that there are three major medium-term oscillations in the pressure field in the summer monsoon period of Southeast Asia of 6-9 days, two weeks and 4-6 weeks. Correspondingly, the ground pressure field shows three kinds of typical eigenvector field distributions, in which the first eigenvector field represents the monsoon circulation and maintains the basic pressure distribution situation. The second and third eigenvectors are superimposed on the basic field Of the disturbance pressure field, which is caused by the monsoon onset, the disruption of the pressure field configuration situation. The above three types can reflect more than 60% of the total amount of information in the field. Cloud field analysis shows that there are also three main forms of cloud field during the monsoon period. One is that the signs of cloud cover change from northeast to southwest opposite; the other is the opposite change of cloud cover between the east and west, and between the south and north These trends are characterized by a strong, weak monsoon and a reaction that advances and retreats in something or between north and south. Weather analysis confirmed that these changes often start from the south. Therefore, this result is of reference to summer tropical weather forecast and mid-term precipitation forecast in our country.