Tropical Cool-skin and Warm-layer Effects and their Impact on Surface Heat Fluxes

Abstract

Abstract Cool-skin and warm-layer effects are important phenomena in the ocean-atmosphere system. Here, we study tropical cool-skin and warm-layer effects and their impact on surface heat fluxes using the methods proposed by Fairall et al. in 1996, i.e., the F96 cool-skin scheme and the combined warm-layer method. The results reveal strong cool-skin effects (~−0.3 K) in the Indo-Pacific warm pool, but weak effects in the equatorial Pacific and Atlantic cold tongues. The spatial pattern of the cool-skin effect is determined by the difference in the specific humidity between the sea and air. The warm-layer effect is strong (~0.25 K) in both the warm pool and cold tongues but weak in the trade wind regions and exhibits a spatial pattern that is inversely related to the surface wind speed. In the tropics, the cool-skin effect causes an average reduction of 11.0 W m −2 in the heat loss from the ocean to the atmosphere, while the warm-layer effect causes an increase of 6.0 W m −2 . With respect to the F96 cool-skin scheme, four common wind speed-dependent empirical models could not fully capture the spatial distribution of the cool-skin effect. A new empirical model that depends on the sea-air humidity difference is proposed to overcome this problem. Compared to the combined warm-layer method, when only the F96 warm-layer scheme is applied, the effect is underestimated at both low and high wind speeds. These new findings improve our understanding of the cool-skin and warm-layer effects and provide insights into their parameterization schemes.