Changes of East Asian summer monsoon due to tropical air-sea interactions induced by a global warming scenario

Abstract

The changes of the East Asian summer monsoon (EASM) in response to increased CO2 atmospheric forcing are analyzed using the Super-Parameterized Community Climate System Model version 4 (SP-CCSM4). In response to the global warming caused by the increased atmospheric CO2 concentration, the precipitation and circulation of the EASM intensify. These changes are explained by the westward extension of the western North Pacific subtropical high (WNPSH). The displacement of the WNPSH is caused by two mechanisms: (i) the increase of sea surface temperature and (ii) the reduction of latent heat flux over the South China Sea and adjacent western Pacific Ocean. The changes in the surface fluxes over the tropics induce a Gill-type anticyclonic circulation in the lower troposphere to the north of the heating anomaly and a Rossby wave train from the tropics into the mid-latitude Pacific Ocean. The westerly anomalies on the northern side of the anticyclone strengthen the southwesterly flow on the western edge of the WNPSH. This flow further affects the wind anomalies and moisture transport over East Asia. The Rossby wave train affects the large-scale circulation associated with the WNPSH.