Instability of the East Asian summer monsoon-ENSO relationship in a coupled global atmosphere-ocean GCM

We use a 300 years 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 Nino 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 characteristics of climatic variables during their high correlation periods (HCP) are quite different from those during the low correlation periods (LCP). Notably, the HCP is characterized by an anomalous low tropospheric cyclone coupled with an anticyclone circulation over the western North Pacific and by a board band of strong low tropospheric easterly wind anomalies located from the Philippines to the Bay of Bengal. For 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 in China and simultaneous Nino3 region sea surface temperature anomalies are significantly different during the HCP and LCP.