Spatio-temporal evolution characteristics and prediction of dry–wet abrupt alternation during the summer monsoon in the middle and lower reaches of the Yangtze River Basin

Abstract

Summer rainfall anomalies have often posed a major water concern in China, and the variations and prediction of dry–wet abrupt alternation (DWAA) events have been receiving increasing attention from researchers. Based on precipitation and atmospheric circulation indices in the middle and lower reaches of the Yangtze River Basin, the spatio-temporal evolution characteristics and predictability of DWAA events were analyzed by calculating the dry–wet abrupt alternation index and selecting early warning signals. The results indicate that most long-cycle and short-cycle DWAA events, except in the period of May–June, are wet-to-dry (WTD) events and that the frequencies and intensities of WTD events have gradually decreased over time. The spatial distribution characteristics on the south shore of the Yangtze River are opposite to those on the north shore. Occurrences of DWAA events can be predicted to some extent by comparing the actual and critical values of select early warning signals. The results also indicate that the BP neural network model exhibits strong performance in simulating the occurrences of DWAA events and therefore may provide a useful reference for intraseasonal wet and dry management in the Yangtze River Basin.