长江三峡库区连阴雨的气候特征分析

An Analysis on the Climatic Characteristics of Consecutive Rainfall in the Three Gorges Area

本文利用长江三峡库区34个气象站1961～2001年的逐日降水资料,分析了库区连阴雨发生频次、持续时间的时空分布特征。结果表明,近40多年来,长江三峡库区年及秋季降水日数以及春、秋季降水量都存在减少趋势。降水量和降水日数的变化会导致连阴雨天气特征发生一定改变。统计表明,近40多年来,库区平均年连阴雨频次有微弱的减少趋势,主要发生在库区西部和南部地区,这种减少趋势主要是由于秋季连阴雨的减少造成的。按照连阴雨影响范围和严重程度的年型划分的统计结果也表明,库区秋季连阴雨在近40多年来有明显的减弱,1960年代至1970年代中期是三峡库区秋季连阴雨的多发季节,秋雨影响范围广、程度重,1970年代后期以来,特别是1990年代后期,秋季连阴雨影响程度明显减弱。

Based on daily precipitation data of 34 stations in the Three Gorges Area during the period 1961 to 2001, the climate characteristics of the consecutive rainfall is analyzed. The results show that decreasing trends can be detected in annual rain days in the Three Gorges Area, as well as rain days in autumn. Additionally, there are decreasing trends in precipitation in spring and autumn. The variation in precipitation and rain days will result in changes of the climatic features of consecutive rainfall. During the recent 40 years, the average annual frequency of consecutive rainfall has a slight decreasing trend in the Three Gorges Area. This decreasing trend mainly occurs in west and south regions of the Three Gorges Area. And the decreases of the frequency of consecutive rainfall in autumn contributed most to the annual decreases. According to the intensity and the affected areas, the annual scale of consecutive rainfall for the whole Three Gorges region was also established. The period 1960s to mid-1970s was the frequent time for consecutive rainfall in autumn in the Three Gorges region. Since late 1970s, especially from late 1990s, consecutive rainfall in autumn decreased significantly.