1998年长江大洪水与大气环流和海温异常分析

ANALYSIS ON THE ABNORMALITY OF GENERAL CIRCULATION AND SEA TEMPERATURE IN RELATION TO THE FLOOD WATER OF YANGTZE RIVER IN 1998

概述了引起1998年长江大洪水的雨情。从天气气候角度分析了1998年长江流域降水异常偏多的原因。指出最直接的原因是副高移动的反常,特别7月15日以后副高突然南撤导致“二度梅雨”天气出现是主要原因之一。对其它诸多大气环流因子和海温异常,如1998年南海季风爆发晚、南亚和东亚季风强度偏弱、夏季赤道辐合带偏弱、热带地区台风生成少、生成时间晚、登陆台风少、亚洲地区上空长期出现阻塞高压、1997年12月至1998年2月青藏高原降雪异常偏多、1997～1998年东太平洋赤道附近发生了本世纪以来最强的一次厄尔尼诺现象等也进行了分析。

Rain fall regime causing flood water of Yangtze River in 1998 is described in this paper.The reason of abnormally heavy rainfall in Yangtze River is analysed from angles of weather and climate.It is concluded that the main reason was the unusual movement of subtropical high and especially the subtropical high suddenly withdrew to south and the weather phenomena of plum rains occurred twice over the Yangtze basin.Other factors of general circulation and phenomena of atmosphere are analysed in this paper,e.g.,the monsoon of the South China Sea broke out late in 1998,the feeble intensity of the monsoon in South Asia and East Asia,and the weakness of the equatorial convergence zone in summer.More over tropic typhoon occurred both sparsely and late,with only a few landings;blocking high persisted over Asia,and the abnormally heavy snow in the Qinghai Xizang Plateau from December 1997 to February 1998.Another main reason causing the flood was the El Nino effect,which was the most intense in the century nearby the equator of East Pacific Ocean from 1997 to 1998.