Abstract:

Based on the daily precipitation of 83 weather stations in Jiangxi Province and daily atmospheric circulation reanalysis data from the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR)  from 1961 to 2015, as well as the real-time Madden-Julian Oscillation (MJO) index during 1975-2015 from Australian Bureau of Meteorology, the characteristics of large-scale atmospheric circulation and water vapor transport of the heavy rainfall processes from 2 to 22 June 2015 in Jiangxi were analyzed, firstly. Then the possible relation between MJO and the heavy rainfall processes in June 2015 in Jiangxi were discussed by using the composite and diagnosis methods. The results are as follows: (1) The anomaly of atmospheric circulation over the Northern Hemisphere was obvious during the severe rainfall from 2 to 22 June 2015, the atmospheric circulation appeared an obvious pattern with “one trough and one ridge” over the Eurasia on 500 hPa geopotential height field, and the western Pacific subtropical high was stronger and the position was westward, which was benefit to the moisture transfer of warm and moist flow to northward. The cold and warm air met over 30°N of China, which caused the heavy rainfall in the middle and north of Jiangxi Province. (2) The strong MJO event was an important impact factor during the heavy rainfall processes in June 2015 in Jiangxi. MJO convection was remarkably active over the Indian Ocean and surrounding regions in early to middle June 2015, which was corresponding to three heavy rainfall processes. The rainfall in Jiangxi had distinct differences at eight phases of MJO convection from west to east. When the MJO convective body moved to Indonesia and the position of the northwestern Pacific subtropical high was westward than normal, it would cause the occurrence of severe rainfall in Jiangxi. Accompanied by the moving of MJO to eastward, the subtropical high withdrew eastward, it wasn’t conductive to the occurrence of rainfall in Jiangxi. It would be potentially helpful to understand and forecast the developing trend of extended range weather by studying the activity rule of the centre of MJO convection.

Key words: heavy rainfall, large-scale circulation, MJO, Jiangxi

摘要：

利用热带大气季节内振荡(Madden-Julian Oscillation，MJO)指数实时资料及NCEP/NCAR逐日再分析资料，对2015年6月江西省强降水期间的大尺度环流、水汽输送及其与MJO的可能联系进行诊断分析。结果表明：2015年6月2—22日强降水期间北半球环流形势异常明显，欧亚中高纬范围为明显的“1脊1槽”分布，西太平洋副热带高压偏强、偏西，有利于大量暖湿气流向北输送，并与南下冷空气在30°N附近交汇，从而使江西中北部出现强降水。2015年6月强MJO过程可能是引发江西强降水的一个重要影响因子。MJO对流6月上中旬在印度洋附近地区异常活跃，西太平洋副高偏强、偏西，有利于副高西北侧水汽输送加强，易引发降水，对应江西出现3次强降水过程，致使江西6月降水出现正异常。伴随着MJO的东传，副高逐渐东撤，不利于江西出现降水。利用MJO发展趋势，对于江西强降水过程延伸期预报具有一定的参考意义。

关键词: 强降水, 大尺度环流, 热带大气季节内振荡, 江西