Modulation of ocean skin temperature by swell waves

Abstract

Infrared measurements of sea surface temperature from R/P Flip in the deep ocean show that there is significant modulation of ocean skin temperature by swell waves and that the wind plays a dominant role in the process. The squared coherence and the magnitude of the transfer function between the skin temperature and surface displacement respond to the wind speed, while its phase is determined by the direction of the wind relative to the swell. When the swell and wind are in the same direction, the transfer function phase indicates that the maximum skin temperature occurs on the forward face, which, in this case, is also the downwind side. Remarkably, the phase changes by roughly 180° when the wind direction reverses from going with the swell to going against it, so that the maximum switches to the rear face, which is again downwind. The peak‐to‐peak modulation T 0 is found to be correlated with the bulk‐skin temperature difference Δ T . Furthermore, T 0 is of the same order as Δ T , suggesting that small‐scale wave breaking due to longwave/shortwave interaction may dominate the phenomenon.