A Similarity Hypothesis for Air–Sea Exchange at Extreme Wind Speeds

Abstract

Hurricane intensity is sensitive to fluxes of enthalpy and momentum between the ocean and atmosphere in the high wind core of the storm. It has come to be recognized that much of this exchange is likely mediated by sea spray. A number of representations of spray-mediated exchange have appeared in recent years, but when these are applied in numerical simulations of hurricanes, storm intensity proves sensitive to the details of these representations. Here it is proposed that in the limit of very high wind speed, the air?sea transition layer becomes self-similar, permitting deductions about air?sea exchange based on scaling laws. In particular, it is hypothesized that exchange coefficients based on the gradient wind speed should become independent of wind speed in the high wind limit. A mechanistic argument suggests that the enthalpy exchange coefficient should depend on temperature. These propositions are tested in a hurricane intensity prediction model and can, in principle, be tested in the field.