Effects of Sea Spray Evaporation and Dissipative Heating on Intensity and Structure of Tropical Cyclone

To examine effects of sea spray evaporation and dissipative heating onstructure and intensity of a real tropical cyclone, the sea spray fluxparameterization scheme was incorporated into the fifth-generationPennsylvania State University--National Center for Atmospheric ResearchMesoscale Model (MM5). Sensitivity tests were performed with varying thespray source function intensities and with and without dissipation heating.The numerical results indicate that sea spray evaporation increases theinterfacial sensible heat flux, which is increased by 16% for themoderate spray and 47% for the heavy spray, but has little effect on theinterfacial latent heat flux. The net effect of sea spray evaporation is todecrease the total sensible heat flux and to increase the total latent heatflux. The total enthalpy flux is increased by 1% and 12% with moderateand strong spray amounts, respectively. Consistent with these results, theintensity of the tropical cyclone is increased by 5% and 16% inmaximum 10-m wind speed, respectively, due to sea spray evaporation. Seaspray evaporation and dissipative heating modify the tropical cyclonestructure in important but complex ways. The effect of sea spray on thenear-surface temperature and moisture depends on the spray amounts and itslocation within the tropical cyclone. Within the high-wind region of atropical cyclone, the lower atmosphere becomes cooler and moister due to theevaporation of sea spray. However, the dissipative heating offsets thecooling due to sea spray evaporation, which makes the lower atmospherewarmer.