Effects of the Sea Surface Roughness and Sea Spray‐Induced Flux Parameterization on the Simulations of a Tropical Cyclone

Abstract

AbstractA tropical cyclone (TC) interacts with the ocean through the interchange of surface fluxes of heat and momentum at the air‐sea interface. The sustainability and intensification of TCs are maintained by the enhancement in the latent heat flux in the high wind speed regime. An accurate calculation of heat fluxes is vital to understand the dynamics of the TC. The sea surface roughness is a crucial parameter that modulates the air‐sea fluxes. A coupled ocean‐atmosphere‐wave model is used to simulate TC Vardah over the Bay of Bengal during 10–15 December 2016. The study focuses on the influence of sea surface roughness on the heat fluxes, track, and intensity of TC Vardah. Four numerical experiments are performed with different parameterization schemes for surface roughness on the basis of (i) frictional velocity (Charnock), (ii) wave age, (iii) wave steepness, and (iv) a combination of wave steepness and wave age. A change in ocean surface roughness results in the modification of the cyclone track and heat fluxes. However, the effect of sea spray on the simulation of wind intensity of TC Vardah is only marginal. Out of the four experiments, the wave age‐based roughness parameterization was found to improve cyclone track, wind, and, hence, the generation of wind waves on the sea surface. In the case study of TC Vardah, the dynamic sea spray reduces surface wind speed up to 1.5 m/s which is within the uncertainty range of the model. An intercomparison of model experiments reveals the impact of surface heat fluxes on the TC Vardha characteristics.