Sensitivity of Sea-Surface Enthalpy and Momentum Fluxes to Sea Spray Microphysics

Accurate estimates of air-sea enthalpy and momentum fluxes are critically important for hurricane intensity predictions. However, calculating these fluxes is challenging due to the nature of the air-sea transition region. At extreme wind speeds, a substantial amount of sea spray is lofted making it necessary to calculate the sea spray-mediated enthalpy and momentum fluxes. These calculations rely on microphysical equations, which are sensitive to the details of the local environmental conditions. Here we use a microphysical model to show that there exists a threshold wind speed beyond which the net sea spray-mediated enthalpy and momentum fluxes are well-approximated by using the net sea spray mass flux alone. This result supports the hypothesis that at extreme wind speeds, the ratio of the air-sea exchange coefficients becomes independent of wind speed, implying the air-sea flux calculations can be substantially simplified.