020106 西太平洋暖池区海表水温暖异常对东亚夏季风影响的研究

对夏季热带西太平洋暖池区海表水温暖异常年的东亚大气环流做了合成分析,然后用奇异值分解(SVD)方法做了进一步统计检验,揭示了东亚夏季风变异与暖池区海表水温异常的密切关系和它们间最佳耦合模态.结果发现当夏季暖池区暖异常时,在对流层低层西太平洋地区可产生一个强的反气旋偏差环流,使得副热带高压南侧东风气流大大加强,并向西伸展到中南半岛南部,从而影响了东南亚热带和副热带地区西南季风的变化(强/弱).中南半岛至中国东部大陆夏季风增强,赤道东印度洋、南海南部和中部、西太平洋热带地区夏季风减弱.SVD分析还发现经向风和纬向风与海表水温之间各存在两个最佳耦合模态,结果表明,不仅整个暖池海表水温暖/冷异常对东亚大气环流异常有重要影响,而且暖池区内海表水温有显著的暖和冷异常差异时,对东亚大气环流的影响也很明显(耦合总体平方协方差约占总体协方差的0.20),尤其是在南海至长江以南地区.

A Composite Study of the Influence of SST Warm Anomalies over the Western Pacific Warm Pool on Asian Summer Monsoon

Based on NCEP reanalyzed data, a composite analysis of general circulations and the SST anomalies over the western Pacific warm pool and their statistical verification through the singular val-ue decomposition (SVD) method are made to describe the best coupled patterns between SST and sum-mer monsoon in East Asia, The results show that a very strong anticyclone deviation circulation occurs in the lower troposphere over the western Pacific Ocean along with positive SST anomalies of the warm pool. On the one hand, the anticyclone deviation circulation makes the easterly wind to the south of the subtropical high become stronger and extend to the Indo-China Peninsula, which affects the develop-ment of southwest monsoon in the tropical area of Southeast Asia. On the other hand, the anticyclone deviation results in stronger southerly wind to the southwest of the subtropical high, so the summer monsoon of the subtropical areas, especially the eastern part of China, become much stronger, The ana-lyses of S VD show that there exist two best coupled patterns between SST and zonal, meridional wind, which indicates that the SST anomalies of whole warm pool can affect the general circulation of East Asia, and so can the heterogeneous distribution of SST anomalies.