南印度洋大气垂直环流与江西6月降水的关系

使用江西省82站1959—2016年6月降水资料和NCEP/NCAR逐月再分析资料，研究了南印度洋大气垂直环流与江西6月降水的关系，并运用大尺度局地涡度倾向变化方程诊断了年际、年代际变化引起的局地涡度倾向异常对江西6月降水的贡献，解释了南印度洋大气垂直环流与江西6月降水年际关系发生年代际改变的原因。结果表明南印度洋大气垂直环流与江西6月降水有密切的关系，且两者的年际关系存在年代际变化:（1）二者关系在1960年代末和1990年代初发生了两次转变，1969年前为显著正相关，1969—1989年相关性不明显，1990年后又转变为显著正相关。（2）江西6月降水偏多年，500 hPa上东亚地区从中高纬到低纬为“+ - +”距平符号分布，江西区域异常正涡度，低层南北风距平在江西上空交汇；降水偏少年环流异常则相反。（3）南印度洋大气垂直环流可引起东亚环流异常，使江西区域涡度正异常；但其影响与背景场的变化有关。动力诊断表明，1969—1989年南印度洋大气垂直环流年际异常对江西局地涡度为正贡献，但年代际异常为负贡献，削弱了年际异常的作用；1990—2016年阶段年际异常为正贡献，同时年代际异常也为正贡献，加强了年际异常的作用，使得其与江西6月降水的正相关显著。 

THE RELATIONSHIP BETWEEN VERTICAL CIRCULATION OVER SOUTHERN INDIAN OCEAN AND JUNE RAINFALL IN JIANGXI

Based on the June precipitation data from 82 stations in Jiangxi Province and the NCEP/NCAR monthly analysis data from 1959—2016, the relationship between southern Indian Ocean vertical circulation and June rainfall in Jiangxi is analyzed. The large-scale vorticity tendency equation is used to diagnose the contribution of local vorticity anomalies caused by interannual and interdecadal variations towards June rainfall in Jiangxi, which may explain the possible causes of their changed interdecal relationship. The results show that the southern Indian Ocean vertical circulation is closely related to June rainfall in Jiangxi, and their interannual relationship shows interdecadal changes: (1) Their relationship changed twice in the late 1960s and early 1990s. It was a significant positive correlation before 1969; during 1969—1989, the southern Indian Ocean vertical circulation had no significant correlation with June rainfall in Jiangxi, and during 1990—2016, the relationship changed to significant positive correlation. (2) In the flood years, the anomalies of East Asia from middle high latitude to low latitude is of "+-+" in the 500 hPa potential height field, with positive anomalous vorticity and 850hPa north-south wind intersection in Jiangxi. It is the opposite in drought years. (3) The southern Indian Ocean vertical circulation can cause anomalies of the East Asian circulation, and lead to positive anomalies of vorticity in Jiangxi, which is related to the changes of the background field. Dynamic diagnosis shows that during 1969—1989 the interannual anomaly of the southern Indian Ocean vertical circulation contributed positively to the local vorticity in Jiangxi, but the interdecadal anomaly contributed negatively, weakening the role of interannual anomalies; the period from 1990 to 2016 is a positive phase, strengthening the role of interannual anomalies, making the southern Indian Ocean vertical circulation correlate positively with June rainfall in Jiangxi.