Characteristics of Large-Scale Drought and Flood Alternation in Autumn in the Yangtze River Basin and Associated Weather Situation Alternation
Wang Le
Guo Shenglian
Tan Xin
Dong Xuan
Ma Yiming
Abstract：Autumn drought and flood alternation(DFA)has very serious impacts on water storage in reservoirs,power generation,and water supply in the Yangtze River basin(YRB).This paper analyzed the spatial and temporal characteristics of autumn DFA in the YRB by using the multi-scale standardized DFAI index(MSDFAI),which comprehensively considers the effects of alternation intensity and speed,and the associated weather situation alternation was analyzed from the perspective of the atmospheric driving.The results show that the high incidence areas of autumn drought to flood alternation events(DTF)from 1962 to 2022 in the YRB are mostly located in the middle and lower Jinsha River,upper Yalong River,Jialing,Min and Wu Rivers,Hanjiang River above the Shiquan station,and the Poyang Lake water network,in which the frequency of moderate events is the highest.The range of DTF in the YRB shows a decreasing trend before the mid-90s,and then turn to an increasing trend.Similarly,the intensity of extreme DTF in local areas weaken before mid-90s,and then increase,while the flood to drought alternation events(FTD)are on the contrary.The mode decomposition shows that the second pattern is mainly characterized by consistent DTF anomalies in the north of the main stream of the upper reaches of the Yangtze River and the upper reaches of the Han River(key area).Before the alternation,most of southern China is controlled by negative geopotential height anomalies,and the wind field and water vapor transport in the key area are divergent anomalies,and the vertical direction is controlled by the dry subsiding flow,which is unfavorable to the occurrence of rainfall.One month after the alternation,there is a positive anomaly in the geopotential height in the middle and lower YRB,the west Pacific subtropical high is intensified and extends westward and the northern low-pressure trough extends southward.Meanwhile,the wind field and water vapor transport in the key area shows a converging anomaly,and the vertical direction is controlled by updrafts and conduced to heavy rainfall.The above weather situation transition leads to a DTF event,while the FTD event is the opposite.
Keywords：Yangtze River basinautumndrought to flood alternationweather situationmeteorologyclimatology
Publication Date：2025-09-30
Online Publishing Date：2025-10-15(First online date of this platform, not the publication date of the document)
Pages：14( 3408-3421 )