1998年夏季中国暴雨洪涝灾害的气象水文特征

文章分析了1998年夏季我国长江、嫩江、珠江流域发生的严重洪涝灾害的气象、水文特征及其成因。6月中、下旬珠江、长江、嫩江流域出现了持续性强降水, 局部地区下了大暴雨; 7月下旬长江流域出现了“二度梅”, 湖南、湖北和江西省普降暴雨; 8月上半月嫩江流域再次出现持续性强降水。频繁的强降水使长江、嫩江、华南西江等干、支流水位迅猛上涨, 支流河水不断涌入干流, 使得干流洪峰迭起。雨水和洪峰迭加, 引发了百年一遇的大洪水。1998年7月副热带高压南落是造成长江流域“二度梅”的主要原因。副热带高压、南海季风涌、中高纬冷空气和从青藏高原东移的中尺度对流系统 (MCS) 等4个因子的最佳组配, 有利于长江流域出现持续性强降水。

Meteorological and Hydrological Characteristics of Severe Flooding in China During the Summer of 1998

An extremely great flood occurred over the Yangtze River, Nenjiang-Songhuaji ang regions, and Pearl River during the summer of 1998, its meteorological and h ydrological characteristics and causes are presented. Pearl River, Yangtze Riv er, Nenjiang-Songhuajiang basins had successive heavy rains in the second half o f June. Yangtze River valley experienced the second period of the Meiyu in the l ast ten-day period of July. Heavy rainfalls centered in Zhalantun were observed over Nenjiang-Songhuajiang regions in first half of August. Frequent heavy rai n falls brought about the rapidly rising water level in most part along the middle reaches of Yangtze, Nenjiang, and Pearl River, and led to the greatest floods in the recent 100 years. The southward shifted subtropical high over the West Paci fic was responsible for the second period of Meiyu. The right mixture of subtrop ical high, monsoon swell from South China Sea, cold air mass coming from mid-hi g h latitudes, and MCSs from the Tibetan Plateau contributed to successive heavy r ains over the Yangtze River valley.