南海季风爆发与风向改变指数关系初探

Study on relation between wind direction change index and onset of south China sea monsoon

通过定义一个风向改变指数，探讨了该指数与南海夏季风爆发之间的关系，得到以下主要结论：利用Yamamoto突变检验，定义了南海关键区，南海季风爆发时，850hPa上的风场在该关键区确有突变发生；南海夏季风爆发时的风场突变是全球风场突变的一部分；分析了南海关键区上该指数的空间分布和时间演变，发现30～300hPa平均于5月初风场开始反向，其早于低层风场反向约2周，这对预报南海季风爆发具有启示意义。

A Wind Direction Change Index（Iw ） is designed to research the relations with the south China sea monsoon onset. The results show that by using the Yamamoto testing , the key areas in the south China sea can be defined. There is wind field mutation of the key areas at 850hPa during the south China sea monsoon onset. The reverse of south China sea monsoon is a part of global wind field reverse. I space-time variation of key areas in the south China sea was analyzed. The wind at 300-30hPa begins to reverse in early May, which occurs about two weeks before the lower. It has the important meaning for the forecast of monsoon onset.