Interannual Meridional Displacement of the East Asian Upper-tropospheric Jet Stream in Summer

作     者：林中达 陆日宇 

作者机构：Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100080 Graduate School of the Chinese Academy of SciencesBeijing 100039 Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100080 

出 版 物：《Advances in Atmospheric Sciences》 (大气科学进展（英文版）)

年 卷 期：2005年第22卷第2期

页      面：199-211页

核心收录：

学科分类：07[理学] 070601[理学-气象学] 0706[理学-大气科学] 

基　　金：This work was supported by the Chinese Academy of Sciences(Grant No.KZCX3 SW-221) the National Natural Science Foundation of China under Grant No.40221503 

主　　题：East Asian jet stream western North Pacific subtropical high South Asian high interannual variations meridional displacement 

摘      要：On the interannual timescale, the meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) is significantly associated with the rainfall anomalies in East Asia in summer. In this study, using the data from the National Centers for Environmental Prediction-Department of Energy (NCEP/DOE) reanalysis-2 from 1979 to 2002, the authors investigate the interannual variations of the EAJS s meridional displacement in summer and their associations with the variations of the South Asian high (SAH) and the western North Pacific subtropical high (WNPSH), which are dominant circulation features in the upper and lower troposhere, respectively. The result from an EOF analysis shows that the meridional displacement is the most remarkable feature of the interannual variations of the EAJS in each month of summer and in summer as a whole. A composite analysis indicates that the summer (June-July-August, JJA) EAJS index, which is intended to depict the interannual meridional displacement of the EAJS, is not appropriate because the anomalies of the zonal wind at 200 hPa (U200) in July and August only, rather than in June, significantly contribute to the summer EAJS index. Thus, the index for each month in summer is defined according to the location of the EAJS core in each month. Composite analyses based on the monthly indexes show that corresponding to the monthly equatorward displacement of the EAJS, the South Asian high (SAH) extends southeastward clearly in July and August, and the western North Pacific subtropical high (WNPSH) withdraws southward in June and August.