Aggravation of Record‐Breaking Drought over the Mid‐to‐Lower Reaches of the Yangtze River in the Post‐monsoon Season of 2019 by Anomalous Indo‐Pacific Oceanic Conditions

Abstract

Abstract The Mid‐to‐Lower Reaches of the Yangtze River (MLRYR) suffered an extreme drought in the post‐monsoon season of 2019, contemporaneous with a strong Central Pacific (CP) El Niño and a super positive Indian Ocean Dipole (pIOD) event. The present work shows that CP El Niño‐related Pacific Sea Surface Temperature Anomalies (SSTAs) weakened the western North Pacific anticyclone to prevent moisture transport to the MLRYR and explained 60% of the drought intensity. The super pIOD with an extremely cold SSTA in the tropical Southeastern Indian Ocean contributed 40% of the drought amplitude via an atmospheric teleconnection. The Indian Ocean cold SSTAs first strengthened the post‐monsoon rainfall and enhanced diabatic heating over South Asia, leading to baroclinic circulation anomalies with induced descending motion over the MLRYR. The aggravated dry conditions there ultimately broke the historical drought record for the period since 1979.