近40年长江流域秋季长周期旱涝急转的变化特征分析

Variations of Autumn Long-Cycle Drought-Flood Abrupt Alternations during Recent 40 Years in Yangtze River

摘要: 本文利用长江流域225个地面站点1979年到2017年近40年内的日降水资料，通过定义长周期的旱涝急转指数，来研究秋季长江流域的旱涝急转的变化特征(分别为旱转涝和涝转旱这两种形式)。通过对旱涝急转频次以及环流背景的特征的分析，讨论了长江流域的显著旱涝急转的现象，结果表明：1) 从近40年长江流域秋季降水的空间分布情况上来看，长江流域中金沙江流域上游地区降水量较少，而嘉陵江流域的下游地区、鄱阳湖东部地区和岷江流域降水量较多；2) 近40年长江流域站点秋季旱涝急转的发生频次较多，长周期旱涝急转以涝转旱事件为主；3) 近40年高强度旱转涝事件多发生在川渝地区，高强度涝转旱事件多生在湖南地区，即洞庭湖流域，其次存在于下游地区。

Abstract: Based on the daily precipitation data of 225 surface stations in the Yangtze River Valley during the past 40 years from 1979 to 2017, the characteristics of drought-flood abrupt alternations in autumn are studied by defining a long-cycle drought-flood abrupt alternations index (drought-to-flood and flood-to-drought). Based on the analysis of the frequency of drought-flood rapid transition and the characteristics of circulation background, the phenomena of drought-flood abrupt alternations in the Yangtze River Valley are discussed. The results show that: 1) From the spatial distribution of autumn precipitation in the Yangtze River Basin in the past 40 years, the upper reaches of Jinsha River in the Yangtze River Basin have less precipitation, while the lower reaches of Jialing River Basin, the eastern part of Poyang Lake and Minjiang River Basin have more precipitation; 2) In the past 40 years, drought and flood in autumn occurred frequently at stations in the Yangtze River Valley, and the long-term drought and flood turned to drought events mainly; 3) In the past 40 years, the high-intensity drought-to-flood events mostly occurred in Sichuan and Chongqing, and the high-intensity flood-to-drought events mostly occurred in Hunan, that is, the Dongting Lake Valley, followed by the downstream areas.