东亚和南亚夏季风气候特征分析

The Analysis of Climatological characteristics of the Summer Monsoon Over the East Asia and the South Asia

利用１９８２～１９９６年的ＮＣＥＰ再分析资料对东亚地区和南亚地区夏季风的气候特征进行了分析．结果表明：①东亚地区夏季风环流圈的建立比南亚地区夏季风环流圈的建立大约早５个候．②东亚地区低层西风存在２次持续加强过程，而南亚地区低层西风的加强则无明显的阶段性．③西南风首先于４月第４候出现在２５°Ｎ，５月第４候向北推到７５～１２５°Ｎ，于６月第３候影响到３０°Ｎ．２２５°Ｎ以北西南风减弱南撤迅速，以南则减弱南撤缓慢．６～９月间，整个东亚和南亚夏季风区存在明显的波动．④积云对流区在东亚地区的主要特征表现为５月４候的突变，而在南亚地区的主要特征则表现在６月３候的突变．即ＯＬＲ场的变化与东亚和南亚夏季风的进退有密切关系。

The NCEP reanalysis daily data from 1982 to 1996 are used to study some climatological characteristics of the summer monsoon over East Asia and South Asia. The results show that: ① The onset of the cell of summer monsoon circulation over East Asia is nearly 5 pentads earlier than that over South Asia, while the withdrawing of the summer monsoon from the mainland of China is about 5 pentads later than its withdrawing from Indian continent;② The East Asian summer monsoon undergoes two stages of continuous enhancement of the west wind at 850 hPa, however, no obvious stages of the enhancement of the west wind at 850 hPa over the South Asia after the onset of the related summer monsoon are observed;③ In summer monsoon region (R1) of East Asia, the low level southwest wind at 850 hPa appears first at 2 5°N in late April. It advances northward to the latitude belt of 7 5 to 12 5°N in late May and of 30°N in the middle June. The southwest wind retreats southward abruptly over the area to the north of 22 5°N and slowly over the area to the south of 22 5°N; ④ The abrupt change in distribution of OLR over the East Asian summer monsoon region occurs with high OLR suddenly retreating eastward to the west Pacific Ocean during the fourth pentad of May,while the abrupt change over the South Asian summer monsoon region with high OLR suddenly northward to northern area of India during the third pentad of June.