Wave activities characteristics during a sudden sharp drought–flood turn event in 2011 in East China

Abstract The sudden turn from drought to flood (STDF) is an extreme climate event that frequently occurs over the middle and lower reaches of the Yangtze River Basin (MLYR) in China. This study investigates the role of the intraseasonal oscillation (ISO) in a STDF event in 2011 over the MLYR and analyses its dynamic characteristics. A wavelet analysis of the rainfall evolution shows that there are two ISO modes (10–20 days and 30–60 days) during the STDF event. When rainfall turns from drought to flood, both ISO modes of rainfall simultaneously convert from the negative phase to the positive phase. Further investigation on the two intraseasonal time scales illustrates that a meridionally‐propagated Rossby wave train (RWT) propagates northward along the eastern China, and meets a zonally‐propagated RWT from the North Atlantic to the North Pacific over the MLYR. The interaction of the two RWTs above is the key factor that causes the STDF event in 2011 over the MLYR.