Sensitivity of enthalpy fluxes to sea spray parameterization in a fully coupled atmosphere-wave-ocean model

Air-sea fluxes are one of the key parameters controlling intensity and intensity change in tropical cyclones. Accurate measurements and parameterization of air-sea fluxes have been lacking. Although recent studies have shown that the momentum exchange coefficient levels off at high wind speed, little is known about the behavior of the exchange coefficient for enthalpy flux in high winds. One of the largest uncertainties is the potential impact of sea spray on the surface enthalpy flux in hurricanes. Here, we examine the sensitivity of high-resolution simulations of Hurricane Frances (2004) to the inclusion of sea spray parameterization developed at NOAA/ESRL in a fully coupled atmosphere-wave-ocean modeling system developed at RSMAS/UM. The spray parameterization is linked to the surface wave properties in the coupled model. To understand the impact of the new spray parameterization, sensitivity simulations are conducted in both uncoupled and coupled modes. In the uncoupled simulation, the droplet-mediated heat fluxes are heavily tied to the wind speed. However, in reality the sea spray generation also depends on a highly variable wave state around the storm for the same wind speed condition. In the coupled simulation, we use the wave energy dissipation to quantify the amount of wave breaking to relate it to the sea spray generation. Preliminary results indicate that the spray parameterization coupled to the waves may be an improvement compared to uncoupled and wind speed dependent only parameterizations compared to some limited observations. Further experiments are in the process to determine how a physically based parameterization of the surface heat fluxes would impact storm intensity.