21世纪长江中下游梅雨的新特征及成因分析  

New Features of Meiyu over Middle-Lower Reaches of Yangtze River in the 21st Century and the Possible Causes

作　　者：蒋薇 高辉[2] 

机构地区：[1]江苏省气候中心,南京210008 [2]国家气候中心,北京100081

出　　处：《气象》2013年第9期1139-1144,共6页Meteorological Monthly

基　　金：江苏省气象科研开放基金项目(KZ201103);科技部国际合作项目(2009FDA23010);公益性行业(气象)科研专项(GYHY201106017)共同资助

摘　　要：利用1961—2011年观测资料分析了长江中下游梅雨各特征量的时空变化特征,尤其是21世纪的新特征,指出2000年以来梅雨入梅偏晚,出梅偏早,梅雨长度缩短,强度减弱。统计发现,在这一时段梅雨期内降水日数明显减少,在梅雨长度缩短的同时,降水日数占梅雨期长度的比例也下降,表明梅雨期内强降水越来越集中。梅雨的这种年代际变化可能和2000年以来北太平洋海温处于PDO负位相,且这一时期拉尼娜事件频繁发生有关。在PDO负位相背景下,我国汛期多雨带位置易偏北,同时由于拉尼娜事件频发,热带西太平洋海温增高,使副热带高压偏强偏西偏北,阻止了源自印度洋和孟加拉湾的西南气流向长江中下游地区的输送,迫使水汽输送路径更加偏北偏西至淮河及以北地区,长江中下游地区低层为正散度距平,梅雨降水减少。Basic characteristics of the Meiyu over the middle-lower reaches of Yangtze River in 1961--2011 are investigated by using the updated precipitation data, especially for the new features in the 21st century. The results indicate both the length of Meiyu period and rainy days reduce in recent decade, and the Meiyu amount also decreases. This change could be attributed to the negative Pacific Decadal Oscillation （PDO） and the increased frequency of the La Nina events in the 21st century. Under the negative PDO phase, rainfall above normal always occurs in northern China, especially in the regions north of the Huaihe River Valley. As a result of the more frequent La Nina events, the SSTs over the western Pacific warmer pool increase in recent decade and force the western Pacific subtropical high to be stronger and more westward and northward. Thus the warmer and wetter southwesterly moisture over the Bay of Bengal and the tropi- cal Indian Ocean has been transported to the regions north of the Huahe River Valley instead of the Meiyu areas. This is a possible cause of the decrease of the Meiyu in the 21st century.

关 键 词：梅雨 PDO ENSO 西太平洋副热带高压 

分 类 号：P461[天文地球—大气科学及气象学]