长江中下游地区梅雨期异常年降水及大气热源分布特征

Characteristics of Rainfall and Atmospheric Heat Source over the Middle-lower Reaches of the Yangtze River during the Years of Abnormal Meiyu Period

根据国家气候中心整编的1951-2011年长江中下游地区梅雨特征量,利用1982-2011年中国800余站点的逐日降水资料和NCEP/NCAR再分析资料,采用气候诊断方法,针对入梅早梅雨期长、入梅晚梅雨期短的两类梅雨降水特征及相应的大气环流差异分别进行了研究;同时对梅雨期间两类梅雨异常的大气热源<Q1>的变化特征差异也进行计算和初步分析。结果表明:早梅年梅雨期降水范围广、雨带偏南,500 h Pa副热带高压北界北跳至25°N的时间较早,梅雨期100 h Pa流场自伊朗高原经青藏高原到东亚东部被反气旋环流控制,仅存在一个反气旋环流中心,高原南侧的热带东风急流范围小,强度弱;而晚梅年则不同,500 h Pa副热带高压北界北跳至25°N的时间晚,梅雨期100 h Pa流场表现为两个独立的反气旋环流中心,高原南侧的热带东风急流范围大,强度强。早梅年梅雨期整体<Q1>的数值和范围都较大,特别是青藏高原南侧、孟加拉湾地区以及长江中下游地区,早梅年<Q1>的大值中心范围更大,强度也更强,而晚梅年则明显与其相反。

Based on 1951-2011 Meiyu characters data over the middle-lower reaches of the Yangtze River from National Climate Centre,the daily rainfall data of more than 800 sites in Chin from 1982-2011 and the NCEP/NCAR daily reanalysis data,and the climate diagnosis method,the precipitation characteristics and the differences of general atmospheric circulation of the early-long Meiyu years and late-short Meiyu years are respectively been analyzed; at the same time,the atmospheric heating source/sink〈Q1〉during Meiyu period is computed and analyzed. The results showed that： the precipitation band is wide and south during Meiyu period of early Meiyu onset years,the time of subtropical high north border at 500 h Pa jump northward to 25 °N is early,the streamline at 100 h Pa is a anticyclonic circulation from the Iranian plateau to the east Asia and there is only one anticyclonic circulation center during Meiyu period,the tropical easterly jet at south of plateau is small and weak. But things are different during Meiyu period of late Meiyu onset years,the time of subtropical high north border at 500 h Pa jumpnorthward to 25 °N is later and there are two independent anticyclonic circulation centers at 100 h Pa,the tropical easterly jet is wide and strong. The total atmospheric heating source in early-long Meiyu years are large and strong,especially in the south of the Tibet Plateau and the bay of Bengal and the middle-lower reaches of the Yangtze River,which are different in late-short Meiyu years.