东亚夏季风的演变特征及其与热带海温的联系

Evolution of East Asian Summer Monsoon and Its Relationship with Tropical SST

摘要: 为了探讨东亚夏季风的演变特征及其与热带海温的联系，本文利用欧洲中期天气预报中心(ECMWF)的ERA5海洋表层海温、降水、重力势、850 hPa、500 hPa和200 hPa风场再分析资料，通过小波分析、合成分析、相关分析等方法，研究讨论了1979~2020年的东亚夏季风的演变特征，其次探讨了异常夏季风年的环流形势与降水，最后讨论了东亚夏季风与热带海表温度的相关联系。结果表明：1) 东亚夏季风有着明显的年代际变化特征，在近40年，东亚夏季风有2~8年的周期变化。2) 在弱东亚夏季风年，中层在华中地区有反气旋式环流异常，低层在东南地区海上有反气旋式环流异常，西北太平洋海上在高中低层都有气旋式环流异常，有利于长江流域降水量偏多，华南和华北部分地区降水量偏少，强东亚季风年的情况基本相反。3) 与东亚夏季风有着较好超前相关的关键区域有赤道中东太平洋，热带大西洋以及印太交汇区。印太交汇区的海温与东亚夏季风的相关性在前秋和前冬基本呈现为正相关，但在前春表现为不同的相关性，在同期夏季则呈现为强的负相关关系；赤道中东太平洋与东亚夏季风的相关性由前秋的负相关逐渐加强，并在前冬达到高值，于前春明显减弱，在同期的夏季呈现为正相关关系；热带大西洋与东亚夏季风的相关性与赤道中东太平洋的情况基本相反。

Abstract: In order to explore the evolution characteristics of the East Asian summer monsoon and its relationship with the tropical sea surface temperature, this paper uses the reanalysis data of the ERA5 ocean surface temperature, precipitation, gravity potential, 850 hPa, 500 hPa and 200 hPa wind field of the European Center for Medium-term Weather Forecast (ECMWF), and studies the evolution characteristics of the East Asian summer monsoon from 1979 to 2020 by wavelet analysis, synthesis analysis and correlation analysis. Secondly, the circulation situation and precipitation in the abnormal summer monsoon year are discussed. Finally, the correlation between the East Asian summer monsoon and the tropical sea surface temperature is discussed. The results show that: 1) The East Asian summer monsoon has the obvious characteristics of interannual and decadal variability. In the past 40 years, the East Asian summer monsoon has 2~8 years of periodic variation. 2) In the weaker East Asian summer monsoon years, there is an anticyclonic circulation in central China at the middle level, and it also exists at low layer in the southeast sea. There is a cyclonic circulation over the northwest Pacific sea in middle and low layers. These configurations are conducive to more precipitation in Yangtze River basin and less precipitation in some parts of South and North China. Meanwhile the configuration of the stronger East Asian Summer monsoon years is basically contrary information. 3) The key areas associated with the East Asian summer monsoon are the equatorial Middle East Pacific, tropical Atlantic and Indo-Pacific intersection. The correlation over the Indo-Pacific intersection is basically positive in the pre-autumn and the pre-winter, but opposite in the summer. The correlation over the equatorial Middle East Pacific is strong opposite in the pre-autumn and pre-winter, and it is weakened significantly in the pre-spring and became positive during the summer. The correlation over the tropical Atlantic is basically contrary with that over the equatorial Middle East Pacific.