东亚夏季风的季节内振荡研究

利用动力学因子和热力学因子结合的方法,将东亚夏季风区的西南风与OLR进行了综合处理,构造成东亚季风指数(IM).研究结果表明,该指数既可很好地反映东亚季风区的风场、高度场的环流特征,又能较好地描述我国长江中下游地区夏季降水和气温的变化.通过功率谱和带通滤波结合的方法研究东亚夏季风中的季节内振荡,东亚夏季风区内低频振荡在夏季主要是以30～60天周期的振荡为主;东亚夏季风的季节内振荡在东亚沿海呈波列的形式,并表现为随时间向北传播的季风涌;由于该季节内振荡的波动,造成了东亚热带夏季风在东亚热带和副热带地区活动的反位相关系.

The Intraseasonal Oscillation of East Asian Summer Monsoon

Dynamic factor and thermodynamic factor are combined to develop a new East Asian summer monsoon (EAM) index (I M). This index has a clear physical meaning. The relationships between I M and summer wind filed, GHT and rainfall are studied. The study shows that I M not only reveals the essence of the activities of the EAM over the subtropical area, but also reflects the features of the monsoon circulation. Moreover, it is good at describing the change of the summer rainfall and temperature in the middle and lower reaches of the Yangtze River. A meridianal wave train along the East Asian coast is discovered. It is a 30-60-day intraseasonal oscillation (ISO) and propagates northward. It is revealed that the northward propagation of the ISO wave in the east coast of China is the main cause for the reverse activities of the EAM in the tropical area and the subtropical area respectively.