2000年以来江淮梅雨带北移的可能成因分析

Possible Reasons for Northward Shift of Meiyu Belt in Yangtze-Huaihe River Region During 2000-2005

2000年以来长江中下游地区梅雨量偏少年出现的频率大大增加,梅雨量进入一个相对偏少的时期。观测资料分析表明,2000—2005年江淮梅雨带的位置较1971—1999年向北移动了2个纬距,淮河流域降水增加了20%。采用1971—2005年NCEP/NCAR再分析资料,从高层风场、中层位势高度场、低层相对涡度、垂直速度、整层视热源Q1和视水汽汇Q2等角度分析了近6年大气环流的异常,进一步研究得到:西太平洋副热带高压脊位置的北移、东亚夏季风的加强以及冷空气的减弱,可能是导致2000—2005年梅雨带位置北移的原因。

Since 2000,the probability of deficit Meiyu year has increased and Meiyu rainfall has stepped into a period of decrease in the Yangtze River region.The rainfall observational data show that the axis of Meiyu belt has shifted 2 degrees in latitude northwards and the rainfall has increased by 20% in the Huaihe River region during 2000-2005 in comparison with that of 1971-1999.Therefore,according to the NCEP/NCAR reanalysis data,the anomaly situation of general circulation has been analyzed from the aspects of 200hPa wind field,500hPa potential height field,850hPa relative vorticity field,vertical velocity,apparent heat source（Q1） and apparent water vapor sink（Q2） for the recent 6 years.In the end,the research shows that all of the northward movement of the ridge line location of the West Pacific subtropical high,the reinforcement of the East Asian summer monsoon circulation and the weakening of cold air from the north have contributed to the northward shift of Meiyu belt during 2000-2005 in the Yangtze-Huaihe River region.