1998年东亚夏季风波包传播特征研究

Wave-packet propagation feature of East Asia summer monsoon in 1998

利用NCEP/NCAR 850hPa风场资料和高度场资料,分析了1998年东亚夏季风强弱变化与波动能量传播特征,表明东亚夏季风存在着加强和减弱的阶段性特征,其季风的爆发、加强、北推东扩与波包的加强和传播有显著的联系。在季风加强期,中、低纬地区一般为波包大值区并有波包加强和向东传播。东亚夏季风爆发前,季风加强主要受中低纬度系统能量的东传影响;东亚夏季风爆发后,季风加强期波包的经向传播十分明显,但期间波包也表现出一定的北传特征,表明低纬地区的系统能量也起一定作用。在东亚夏季风减弱期东亚为波包小值区控制,显示出在季风减弱阶段波包能量的传播也有减弱的特征。

The NCEP/NCAR 850hPa wind and high field data are used to analyze the relation between the strength of the East Asia summer monsoon （EASM） and the wave energy propagation in 1998. The results show that the fact that the EASM breaks out, strengthens and spreads to north or east are strongly connected with the wave-packets enhancement and propagation to the north. During the period of monsoon strengthening the big value districts of wavepackets appear in the tropics and mid-latitude region and these value districts spread to east. Before the EASM breaks out the strengthened monsoon is mainly affected by the system energy eastward propagation in the low-mid latitude. After the EASM breaks out the wave-packet propagation in longitude is obvious during the monsoon strengthening, but also has features of northen spread. It explains that the low-latitude system is influenced During the period of the monsoon weakness the East Asia is controlled by big value districts of wave-packets. It shows that in the stage of monsoon weakness the wave-packet propagation is weakened.