20世纪90年代末东亚夏季降水年代际变化及其成因初探

基于1983—2011年月总降水量、环流和海温的再分析资料,给出了20世纪90年代末东亚夏季降水的年代际调整的区域特征,及其对应的大气环流内部过程和可能的海温外强迫的年代际变化.研究结果表明,在20世纪90年代末期东亚北部夏季降水比东亚南部夏季降水由湿向干的表现更为明显,东亚南部地区夏季降水则是在20世纪90年代初和21世纪初发生年代际的转折.此外,东亚地区夏季的500 h Pa高度场、850 h Pa风场、U200风场、水汽输送场和东亚太平洋遥相关型指数和东亚夏季风指数等在20世纪90年代末期也表现出明显的年代际变化特征.进而从大气内部过程的角度验证了20世纪90年代末东亚夏季降水发生的年代际调整.与此同时,北太平洋和西太平洋海表温度表现出由偏低向偏高的转变,这可能是导致20世纪90年代末期东亚夏季气候年代际变化的重要外部成因之一.

Interdecadal variation of precipitation pattern and preliminary studies during the summer of late-1990s in East Asia

Based on the analyses of monthly precipitation, National Centers Environmental Prediction/University Corporation for Atmospheric Research reanalysis dataset, and 2°×2° sea surface temperature (sst) data of extended reconstructed sea surface temperature during 1983-2011, we discuss the interdecadal variations of precipition around late-1990s in East Asia, the contributions of the atmospheric internal dynamic processes, and the extra-forcing factors such as sst that presents interdecal characteristics corresponding to the results obtained by using regress analysis. The results show that the interdecadal variations of the summer rainfall over Northern East Asia around late-1990s were more obvious than over Southern East Asia, and the summer rainfall over Southern East Asia experienced a notable interdecadal change around early-1990s and early-2000s. The summer geopotential height at 500 hPa, the summer wind at 850 hPa, the summer U-wind at 200 hPa, the water vapor transportation field, the index of EAP and EASM all have the notable characteristics of the interdecadal variations, which further validate the interdecadal change of precipition of late-1990s from the angle of the atmospheric internal dynamic process. At the same time the sea surface temperature interdecadal anomalies of North Pacific and West Pacific may also be one of the important reasons for causing the interdecadal change over East Asia of the late-1990s.
Keywords： precipitation pattern interdecadal variation circulation extra-forcing factor