江苏近40a夏季降水异常及其成因分析

Summer Anomalous Precipitation in Jiangsu Province and Its Possible Mechanism

摘要:

利用1961-2000年江苏省60个台站的月降水量资料,研究了江苏夏季(6、7、8月)降水量的异常空间分布特征和时间演变规律,分析了与江苏夏季降水有关的大气环流异常的基本特征及引起江苏降水异常的原因。结果表明:(1)江苏夏季降水异常主要表现出两种最为典型的空间分布。其中,第一类雨型反映了全省降水的一致性变化,表现出整体偏多或偏少的情形;而第二类雨型则反映了降水异常的南北反相分布,对应的降水分布为南多北少或南少北多的形势;(2)两类雨型均存在明显的年际变化,两类雨型均与西太平洋副热带高压的南北异常有密切关系,但二者的大气环流背景场又存在显著的不同;(3)不同区域、不同季节的SSTA与两类降水异常存在一定的相关关系,是造成江苏降水年际异常的可能原因之一。前冬北太平洋SSTA偏暖(冷)通常与江苏夏季降水的整体偏多(少)有关;而前期冬季南印度洋、春季热带印度洋、南海及我国东部沿海地区出现的SSTA大范围的冷(暖)异常,通常对应江苏夏季降水南少(多)北多(少)。

Abstract:

By using the 40a (1961-2000) monthly precipitation data at 60 sites in Jiangsu Province,the spatial and temporal characteristics of summer precipitation anomalies and its related anomalous atmospheric general circulation as well as possible mechanism are investigated.It is found that the anomalies of summer precipitation in Jiangsu Province exhibit two most typical patterns.The first pattern reflects a high spatial consistency of precipitation anomalies,i.e. its general trend;while the second pattern shows an anti-phase relation of precipitaion variation in the northern and southern regions,that is to say,if the precipitaion is more (less) in the southern region,then less (more) in the northern region.Both of the two precipitation patterns exhibit evident interannual variations and are closely related to the latitudinal location of Western Pacific Sub-tropical High (WPSH).However there are still significant differences in their atmospheric circulation background fields.It is also found that SSTAs in different regions and seasons bear intimate relationships to the two precipitaion patterns respectively,which may be one of the factors resulting in the interannual anomalies of Jiangsu summer precipitation.When the SSTA in previous winter in Northern Pacific is warmer (colder),the summer precipitation in all regions of Jiangsu is more (less).Accompanied by the colding (warming) of SSTA in the southern Indian Ocean in previous winter and in the tropical Indian ocean,South China Sea and the sea areas east to the China in spring,the summer precipitation is less (more) in the south and more (less) in the north of Jiangsu.