江南春雨的时空分布及其气候特征

Spatial and Temporal Distribution of the Spring Persistent Rains and Its Climatic Characteristics

本文利用1979~2010年中国753站逐日降水资料,重新定义了江南春雨的时间范围(12~27候)和空间范围(23?~30?N,110?~120?E)。在此基础上,利用NCEP/NCAR再分析资料合成分析了江南春雨的气候态环流特征。结果表明:在江南春雨期间,上游青藏高原东南侧一直存在一个西南风速中心,且江南地区有显著的上升运动,这样的环流配置有利于水汽向江南地区输送,产生降水。在850 hPa高度场上,青藏高原东南侧等位势线较密集,气旋性曲率较大,是西南风增强的重要原因。另外,经向和纬向海陆热力差异都对江南春雨有重要影响,纬向海陆热力差异比经向海陆热力差异稍微强一点,因为它对江南地区春季的降水有很好的对应关系。海陆热力差异很可能是造成江南地区降水的重要影响因子,它也是季风的根本推动力,对于江南地区副热带季风降水性质的定义有重要指示意义。

Based on the daily precipitation data from 753 stations in China during 1979 and 2010, the spatial scale (23? - 30?N, 110? - 120?E) and time range (from pentad 12 to 27) of the Spring Persistent Rains (SPR) are redefined. On this basis, by using the NCEP/NCAR reanalysis dataset, we analyzed the climatic circulation characteristics of the SPR. The results show that during the SPR period, the southwest wind speed center located on the southeast of Tibetan Plateau has always existed, and there is a strong upward motion over the SPR area. This configuration is conductive to water vapor transport to the SPR area and further produces precipitation. In the 850-hPa height field, the equipotential line on the southeast of Tibet Plateau is intensive and the cyclonic curvature here is large, which is an important reason for the enhanced southwest wind. In addition, the meridional and zonal land-sea thermal differences have important effect on the SPR, especially the zonal land-sea thermal differences between East Asia continent and the Western Pacific, for which has a good cor-responding relationship with the SPR. The land-sea thermal differences are likely to be an important cause of the SPR, and it is significant for the definition of the nature of the SPR, because it is the fundamental driving force of the monsoon.