Relative contribution of ENSO and east asian winter monsoon to the south China sea sst anomalies during ENSO decaying years

Abstract

Present study investigates respective contributions of El Niño-Southern Oscillation (ENSO) and East Asian winter monsoon (EAWM) to two periods of sea surface temperature (SST) anomalies in the South China Sea (SCS), one subsequent to the ENSO mature phase and the other in the following summer, during 1982-2010. It is found that the SST anomalies in the first period are related to the EAWM and the ENSO impact independent of EAWM is weak, which differs from previous studies. The SST anomalies in the second period are mainly due to the ENSO effect. A heat budget analysis shows that changes in shortwave radiation and wind-related surface latent heat flux as well as horizontal advections are the processes leading to the EAWM-related SST anomalies in the first period. The ENSO-related SST anomalies in the second period are contributed by shortwave radiation and latent heat flux anomalies as well as meridional advection and vertical upwelling processes near the southeast coast of Indochina Peninsula. The ENSO contribution to the SCS SST anomalies in the first period is larger before than after the late 1970s. This is attributed to an earlier development of ENSO events that is followed by larger equatorial central and eastern Pacific SST anomalies in boreal summer and, subsequently, larger North Indian Ocean SST anomalies around October. Consequently, anomalous surface anticyclone over the SCS is stronger, leading to larger surface heat flux anomalies and thus a larger SST increase around October before than after the late 1970s.