Effects of sea spray on tropical cyclone intensity forecasts with the NCEP global forecasting system

Strong winds in a tropical cyclone over the ocean can produce substantial amounts of spray in the lower part of the atmospheric boundary layer, which can in turn, have a large impact on tropical cyclone intensity by modifying air-sea fluxes. In general, spray droplets produce not only spray-sensible heat flux by heat conduction from spray temperature (which is same as sea surface temperature) to air temperature, but they also produce latent heat flux by their evaporation. The latter process occurs at the expense of cooling the atmosphere. While there is a large uncertainty in the parameterization of the sea spray effect, a feedback mechanism due to the near-surface cooling and moistening makes the parameterization be more difficult. In this study, the impact of spray on the tropical cyclone intensity is investigated using the NCEP Global Forecast System. The effect of spray is included in the form of modified air-sea fluxes, based on the parameterization of Fairall et al. (1994) and Andreas et al. (2008). Sensitivity tests for feedback coefficients are also conducted.