Effects of northern and southern components of the East Asian winter monsoon variability on SST changes in the western North Pacific

Abstract

AbstractThe present study investigates the impacts of the two components of the East Asian winter monsoon (EAWM) variability on sea surface temperature (SST) changes in the western North Pacific. When the EAWM is stronger than normal, significant negative SST anomalies form in the East Asian marginal seas and subtropical western North Pacific and persist from winter to the following spring. It is found that winter‐spring SST anomalies in the Yellow Sea and the Japan Sea have a close association with the northern component of the EAWM variability, whereas the southern component has a large impact on SST changes in subtropical western North Pacific. The two components induce SST anomalies through both surface heat flux and oceanic advection changes. The surface latent heat flux is predominantly responsible for SST changes. The oceanic advection has a secondary contribution to the SST change in subtropical western North Pacific associated with the northern component and in the Japan Sea associated with the southern component. The surface latent heat flux anomalies associated with the northern component are induced through changes in both wind speed and sea‐air humidity difference, and those associated with the southern component are induced mainly through changes in sea‐air humidity difference north of 20°N. The SST anomalies induced by the northern component are mostly independent of El Niño–Southern Oscillation (ENSO). While ENSO has a large effect on the SST anomalies in open oceanic regions, the southern component has a dominant contribution independent of ENSO to the SST anomalies in the marginal seas.