Observed Opposite Fall-to-Winter Variations in the Air-Sea Latent Heat Flux Between the Western Boundary Currents and Coastal Seas

Abstract

This study presents observations of opposite fall-to-winter variations in the air-sea latent heat fluxes (LHs) between the western boundary currents (WBCs) and coastal seas obtained using eight air–sea buoys in the Northern Hemisphere. Different from the WBCs, the wintertime LH along the coast is strangely reduced by approximately 60 Wm−2 compared to that in fall. The reduced sea–air humidity differences account for these opposite seasonal variations, although the sea–air temperature differences are enhanced, while the roles played by winds and the nonlinear effects are minor. The boundary layer stability also varies in terms of the air-sea parameters from fall to winter. However, the conditions of the WBCs meet the traditional expectation: that is, the LH in winter is 60 Wm−2 higher than that in fall with near-neutral/unstable boundary layer stability. Enhanced winds in winter determine the seasonal enhancement of the LH over the WBCs, indicating a specialized regional character.