2011年南海夏季风爆发过程及其与长江中下游梅雨的联系

Onset process of South China Sea summer monsoon in 2011 and its relationship with Meiyu over the middle and lower reaches of the Yangtze River

采用NCEP/NCAR再分析资料、FY2E-TBB及台站降水资料,对2011年南海夏季风爆发前后的环流特征进行分析。结果表明:2011年强对流活动由孟加拉湾扩展到南海地区,同时伴随着南亚高压移至中南半岛北部,西太平洋副热带高压向东撤出南海地区,南海夏季风于5月第4候(第28候)爆发;季风爆发后,印度—孟加拉湾季风槽形成,南海地区低空开始盛行西南气流,并伴有对流降水的发展和温、湿等要素的突变。随着季风活动的推进,我国雨带北抬,长江中下游一带进入梅雨期,出现降水大值区。通过分析发现长江中下游梅雨与南海夏季风均受副热带高压影响,且两者的强度为显著的负相关关系,梅雨开始时间与南海夏季风爆发时间呈显著的正相关关系。2011年南海夏季风偏弱,爆发时间偏早,长江中下游梅雨强度偏强,入梅时间异常偏早。

Based on the NCEP / NCAR reanalysis data,the FY2E-TBB data and the precipitation observed by meteorological stations,the general circulation and precipitation before and after South China Sea（ SCS） summer monsoon onset of 2011 are analyzed. Results show that the convective activity first appears in the Bengal Bay,then extends to SCS in 2011. M eanw hile,South Asia high moves to the northern Indo-China peninsula and the w estern Pacific subtropical high w ithdraw s eastw ard from SCS,and SCS summer monsoon breaks out in the fourth pentad of M ay（ the 28 th pentad of 2011）. After the monsoon onset,the India-Bengal Bay summer monsoon trough forms,andthe southw est flow prevails in low er troposphere over most of SCS,coupling w ith abrupt changes of both the convective rainfall and the circulation over SCS. With the progress of monsoon activity,the rainbelt moves northw ard and the great precipitation appears over the middle and low er reaches of the Yangtze River w here the rainy season begins. It is found that both the SCS summer monsoon and the M eiyu over the middle and low er reaches of the Yangtze River are influenced by the subtropical high. There is an obvious negative correlation betw een intensity of M eiyu over the middle and low er reaches of the Yangtze River and that of SCS summer monsoon,but there is a remarkable positive correlation betw een onset time of the M eiyu and that of SCS summer monsoon. SCS summer monsoon is w eaker and its onset time is earlier,w hile M eiyu precipitation over the middle and low er reaches of the Yangtze River is heavier and its onset time is earlier in 2011.