Does El Niño play an early signal role for the south-flood north-drought pattern over eastern China?

Abstract

Reconstructed hydroclimatic spatial patterns from historical documents, the chronology of El Nino events since 1525, Meiyu (a unique rainy season dominated by the East Asian summer monsoon in eastern China) series since 1736, and a 1000-year control simulation using the Community Earth System Model were used to analyze the occurrence of anomalous summer precipitation patterns over eastern China with El Nino events. The results show that the frequency of the south-flood north-drought during 1525–2005 was significantly higher during El Nino episodes. Specifically, the occurrences of the triple pattern with floods in the Yangtze River Valley but droughts in its north and south (FYRDNS) as well as the dipole pattern with floods in the south but droughts in the north (FSDN) divided by the Yangtze River both increased in El Nino developing years, while the occurrence of FSDN increased in El Nino decaying years. Among 44 severe and extreme Meiyu events over the middle and lower reaches of the Yangtze River in 1736–2016, 75% of events occurred during El Nino episodes. Especially, 80% of extreme Meiyu events occurred in El Nino decaying years. The 1000-year control simulation captured well the reconstructed triple pattern of FYRDNS in developing years and the dipole pattern of FSDN in decaying years, with more noticeable precipitation anomalies for developing years of very strong and extremely strong El Nino events. These results implicated that the El Nino is likely an early signal for the occurrence of the south-flood north-drought over eastern China.