Evidence of spray-mediated air-sea enthalpy flux within tropical cyclones

Abstract

It has long been conjectured that spray ejected from the high-wind ocean surface enhances air/sea enthalpy fluxes, but a lack of observational data, particularly at wind speeds exceeding 20ms-1, has prevented either confirmation or refutation of this hypothesis. The current study has two aims: first, to provide an estimate of surface enthalpy fluxes obtained from dropsonde data and second, to provide evidence of spray-mediated enthalpy transfer. These are accomplished first by assuming that Monin-Obukhov similarity is satisfied throughout the bottom 100m of the high-wind boundary layer, then by focusing on the enthalpy flux HK rather than its transfer coefficient C K. The scaling of HKwith wind speed in observational data sets reveals similarities to spray-mediated fluxes predicted by a newly developed surface flux model, in contrast with measurements made in a laboratory setting. This behavior supports the claim that surface enthalpy fluxes are dominated by spray within tropical cyclones. Key Points Spray dominates enthalpy flux at the hurricane air-sea interface Enthalpy fluxes can be estimated from dropsonde thermodynamic data Trends of enthalpy flux coefficient can be misleading due to uncertainty ©2014. American Geophysical Union. All Rights Reserved.