Instability of the East Asian Summer Monsoon‐Enso Relationship in a Coupled Global Atmosphere‐Ocean GCM

Abstract

AbstractWe use a 300‐year control integration of a coupled global atmosphere‐ocean‐sea ice general circulation model (GCM) to study the relationship between the East Asian summer monsoon (EASM) and the ENSO (El Niño and Southern Oscillation) cycle by applying cross wavelet analysis. Our result reveals that the correlation between EASM and ENSO may break down on inter‐decadal time scales. Furthermore, the features of climatic variables during their high correlation periods (HCP) are quite different from those during the low correlation period‐s (LCP). It is noted that the HCP is characterized by an anomalous low tropospheric cyclone coupled with an anticyclone circulation over the western North Pacific, and by a board belt of strong low tropospheric easterly wind anomalies located from Philippines to the Bay of Bengal. During the HCP large inter‐annual variability is founded in the low tropospheric wind velocity over Southeast Asia, and in the tropospheric temperature and geopotential height over the tropical western Pacific. In addition, the correlation pattern between summer precipitation and simultaneous Niño3 region sea surface temperature anomalies during the HCP are significantly different from that during the LCP in China.