Contribution of Wind Speed and Sea-Air Humidity Difference to the Latent Heat Flux-SST Relationship

This study investigates contributions of wind speed and sea-air humidity difference (dq) terms to the seasonal change and time scale dependence in the relationship between surface latent heat flux (LHF) and sea surface temperature (SST) using daily data. Generally, the dq term is dominant in the SST effect on LHF in the midlatitude SST frontal zones and tropical Indo-western Pacific, and the wind speed term is dominant in the LHF effect on SST in the subtropical gyres and tropical Indo-western Pacific. The seasonal change in the dq term accounts for a larger SST effect in winter than in summer in the midlatitude frontal zones, and that of the wind speed term explains a larger LHF effect in summer than in winter in the subtropical gyres. In the tropical Indo-western Pacific, the dq term is dominant in the SST effect in summer, and the wind speed term is dominant in the LHF effect in winter. The contribution of the dq term to the SST effect increases with the time scale. The contribution of the wind speed term to the SST effect varies regionally: It is supplementary in the midlatitude frontal zones in winter and summer and in the Arabian Sea in summer, but it is opposite in the Philippine Sea in winter and summer and in the South China Sea and Bay of Bengal in summer. The contribution of the wind speed term to the LHF effect is confined to short time scales in most of the tropical Indo-western Pacific regions.