东亚夏季风雨带和西太平洋副高季节变化的耦合特征

SEASONAL COUPLING FEATURES BETWEEN THE EAST ASIAN SUMMER MONSOON RAINBAND AND WEST PACIFIC SUBTROPICAL HIGH

利用NCEP/NCAR数据集中1950～1999年4～9月500 hPa位势高度和逐日降水率(PRATE)资料,通过奇异值分解,主要探讨了东亚夏季风雨带与西太平洋副高季节移动的耦合关系。分析发现,模态方差的大小只反映模态对整个分析时段和整个分析区域贡献的大小,但对某些时段、某些区域来说,方差较小模态的贡献很大;因而仅以模态方差贡献的大小来判定模态的重要性是不完全的,只有多个模态的配合才能比较全面地揭示两个场的耦合特征。结果表明:东亚夏季风雨带在不同地区的跳跃对应着西太平洋副高的三次突变,不同模态对三次突变有不同的贡献。

The precipitation data and 500hPa geopotential height data used in this paper are from NCEP/NCAR data set for the period from 1950 to 1999(from April to September). By using the SVD (Singular Value Decomposition), the seasonal coupling relationship between the transitions of East Asian summer monsoon (EASM) rainband and the west Pacific subtropical High (WPSH) was investigated. We see from the results of the SVD analysis that, the contribution of the modes explaining less squared covariance percentage must be considered for some regions and some periods. Results indicate that the different modes reflect the three abrupt changes separately, and the three abrupt changes of WPSH correspond to the sudden jumps of EASM rainband over the different regions. The multiple monsoon rainfall onsets occur as the major rainbands make rapid transitions to these regions.