中国南方冬季降水异常的时空分布特征分析

Abstract

利用我国南方224个测站，近50a年平均地面降水资料，采用线性趋势分析、EOF、REOF、Mann-Kendall、合成分析等方法，分析了季风区冬季降水异常变化的规律。结果表明：1) 南方冬季降水自西向东递增，高值中心分别在湘东和江浙闽交界区，而在滇北川南有一干舌区，这个干舌区的存在可能是导致西南地区冬季易出现干旱的重要原因之一。近50a南方冬季降水以4.42 mm/10a的速率不显著增多，其中，1月以32.59 mm/10a的速率显著增多，12月和2月不显著。冬季降水经历了两个波动阶段：1960s~1970s中期偏多，1970s后期偏少；1980s~1990s后期以来偏多为主；冬季降水的稳定性，从南北向中部递增，在川东—黔北—湘中一带形成稳定中心。2) 大多数区域冬季降水变化有上升趋势，倾向率从西向东增大，在长江下游的有显著增多趋势，云贵高原有不显著减少趋势，其余地方降水变化趋势不显著增多。3) 冬季降水异常主要有3种分布模态：全区一致型、高原平原差异型和巫山型，这种分布与风场异常有关联。该区冬季降水异常主要分为华南区、长江中下游平原区、云贵高原区3个子区域。4) 各分区的异常干、湿冬年，华南和长江中下游大部分出现在1980年以后，但云贵高原比较分散；长江中下游在1988年有突变现象。各区降水的年际、年代变化差异较大，但进入本世纪都处于减少趋势。Using the mean surface precipitation data from 224 stations of southern China over the years of 1961-2010 and adopting the methods of linear regression analysis, multinomial fitting, EOF, REOF, Mann-Kendall and Glide T-examination etc., we analyzed the spatial anomaly features and time evolution rule of the winter precipitation in southern China. The results show that 1) China Southern winter precipitation increases from west to east; the high value centers are in eastern Hunan-border area of Jiangxi and Zhejiang and Fujian; while in northern Yunnan Southern Sichuan there has a dry tongue area, and the presence of this dry tongue area may lead to winter drought in south-west region. Southern winter precipitation increased slightly with a rate of 4.42 mm/10a in recent 50 years; it increased significantly in January with a rate of 32.59 mm/10a, but it was not significant in December and February. Winter precipitation fluctuations experienced two stages: above normal from 1960s to the mid-1970s, less than normal in the late 1970s; mainly above normal from 1980s to the late 1990s. Stability of winter precipitation increases from north and south to central areas. In eastern Sichuan-Guizhou-Hunan area, it forms a stable center. 2) As to the winter precipitation in most regions, there is an upward trend at a rate increasing from west to east. In the lower reaches of the Yangtze River, there has a significant increasing trend; there is no significant decreasing trend in Yunnan-Guizhou plateau. In the rest of places, precipi- tation trend was not significantly increased. 3) With the EOF method, the abnormity of southern winter precipitation can be divided into three kinds of distributed types, namely entire regional distribution type, plateau and plain opposite distribution type and Wushan type. This distribution may be related with wind anomaly. With the REOF method, the area can be subdivided into 3 sub-areas: the Southern China, the middle and low reach of Yangtze River and the Yunnan-Guizhou Plateau. 4) The dry and wet anomaly in winter, in Southern China and the middle and low reach of Yangtze River in each subarea occurred mostly after 1980, but scattered in Yunnan-Guizhou Plateau; There was a mutation phenomenon at the middle and low reach of Yangtze River in 1988. Inter-annual and decadal variations of the precipitation were greatly different in each subarea, but declined at the beginning of this century.