Atmosphere-ocean relationship in the midlatitude North Pacific: Seasonal dependence and east-west contrast

The present study documents the relationship between the surface heat flux and sea surface temperature (SST) and estimates the contribution of different processes to SST changes in the midlatitude North Pacific. It is found that the atmosphere-ocean relationship displays pronounced differences between winter and summer and between the western and central basins of the North Pacific. In the western basin, the shortwave radiation change associated with a positive cloud-SST feedback is a dominant factor for the development of SST anomalies in boreal summer. In boreal winter, surface latent heat flux anomalies develop in response to SST and in turn damp the SST anomalies. The meridional advection induced by anomalous geostrophic currents near the coast and by anomalous Ekman currents away from the coast has important contributions to the SST changes. In the central basin, the latent heat flux change is a dominant factor for the development of SST anomalies, and the shortwave radiation mainly responds passively to SST anomalies in boreal summer. Both latent heat flux and meridional advection contribute to the SST changes in boreal winter. The wind changes over the North Pacific play an important role for the SST changes both in winter and summer through their impacts on cloud, surface wind speed, advection of atmospheric boundary layer moisture, and Ekman transport.