东亚夏季风的年际变化及其与环流和降水的关系.doc

东亚夏季风的年际变化及其与环流和降水的关系 YU Shuqiu1，SHI Xiaohui1，LIN Xuechun2 1. State Key Laboratory of Severe Weather; Chinese Academy of Meteorological Sciences; Beijing 100081; China; 2. National Climate Center, China Meteorological Administration, Beijing 100081, China Abstract: Using NCEP/NCAR reanalysis geopotential height (GHT) and wind at 850hPa, GHT at 500hPa, precipitation rate, sea level pressure (SLP) and precipitation observations from more than 600 stations nationwide in June–August from 1951 to 2006, and focusing on the East Asia–West Pacific region (10o–80oN, 70o–180oE), interannual variation of East Asian summer monsoon (EASM) and its correlations with general circulation and precipitation patterns are studied by using statistical diagnostic methods such as 9-point high pass filtering, empirical orthogonal function (EOF) analysis, composite analysis and other statistical diagnosis, etc. It is concluded as follows: (1) EOF analysis of SLP in the East Asia–West Pacific region shows the existence of the zonal dipole oscillation mode (APD) between the Mongolia depression and the West Pacific high, and APD index can be used as an intensity index of EASM. (2) EOF analysis of GHT anomalies at 500hPa in the East Asia–West Pacific region shows that the first EOF mode is characterized with an obvious meridional East Asian pattern (EAP), and EAP index can also be used as an EASM intensity index. (3) The composite analysis of high/low APD index years reveals the close correlation of APD index with EAP at 500hPa (or 850hPa). The study shows an obvious opposite correlation exists between APD index and EAP index with a correlation coefficient of –0.23, which passes the confidence test at 0.10level. (4) Both APD and EAP indexes are closely correlated with precipitation during flood-prone season in China and precipitation rate over the East Asia–West Pacific region. The significant correlation area at 5% confidence level is mainly located from the southern area of the Yangtze Ri