Summer Intraseasonal Surface Heat Flux-Sea Surface Temperature Relationship Over Northern Tropical Indo-Western Pacific in Climate Models

The present study documents the relationship between intraseasonal net surface heat flux (NHF, positive for downward flux) and sea surface temperature (SST) variations over the North Indian Ocean and tropical western North Pacific during May through September in climate models. A distinct NHF-SST relationship is identified in the NCC.NorESM1-M model. NHF has a weak correlation with the SST tendency but a large negative correlation with SST in the NCC.NorESM1-M model, whereas NHF has a large positive correlation with the SST tendency and a weak correlation with SST in observations and some other climate models. The sea-air humidity difference has a dominant contribution to latent heat flux variations in relation to a bias toward larger mean wind speed in the NCC.NorESM1-M model. In contrast, surface wind speed overcomes the sea-air humidity difference in contributing to latent heat flux variations due to a bias toward larger mean sea-air humidity difference in the INM.inmcm4 model. Detailed analysis reveals different processes in intraseasonal SST variations in the South China Sea between the INM.inmcm4 and NCC.NorESM1-M models. In the INM.inmcm4 model, atmosphere-induced shortwave radiation and latent heat flux have a main contribution to the SST change. In the NCC.NorESM1-M model, the SST change is mainly due to oceanic processes. The ocean-induced positive SST anomalies increase evaporation and surface air humidity. This destabilizes the atmospheric boundary layer in favor of convection and reduced downward shortwave radiation. NHF has a damping effect on the SST change.