对东亚夏季风与西北太平洋热带气旋频数关系的初步分析

A Study of the Relationships between the East Asian Summer Monsoon and the Tropical Cyclone Frequency in the Northwestern Pacific

利用海陆热力差指数 (ILSTD)、 5 0 0hPa位势高度场、向外长波辐射 (OLR)资料及NCEP/NCAR月平均再分析数据集 ,分析东亚夏季风与西北太平洋地区 (包括中国南海 )热带气旋频数的关系 ,结果表明 ,在强夏季风年西北太平洋地区热带气旋频数偏多 ,而弱夏季风年同期热带气旋频数异常偏少而后期趋于正常 ,正常夏季风年热带气旋频数基本正常。并结合热带气旋形成的大尺度环流条件 ,对其动力机制作了初步探讨。

The relationships between the East Asian summer monsoon and the generating frequency of tropical cyclone in the northwestern Pacific (including the South China Sea) are investigated in the context of the index of land-sea thermal difference (I LSTD), 500 hPa height fields, OLR data, and NCEP/NCAR monthly mean reanalysis data. Results show that the change of intensity of the summer monsoon bears a close relation to the frequency of tropical cyclone in the northwestern Pacific. In strong summer monsoon years, the number of tropical cyclone in the northwestern Pacific is larger than normal while in weak years the contrary is the case in the synchronous season and the number of tropical cyclone is normal in the subsequent season. Furthermore, based on the large-scale conditions of tropical cyclone generating, its dynamic mechanism is discussed.