Mechanical Effect of Sea Spray on Tropical Cyclone Intensity under Idealized Conditions

Sea spray affects a Tropical Cyclone (TC) both thermodynamically and mechanically. The purpose of this work is to study the mechanical effect of the spray on the idealized hurricane dynamics. This has been achieved through implementation of the mathematical model that describes spray-turbulent flow interaction into the numerical weather prediction code. The mathematical model (Rastigejev et al., 2011) is based on the Monin-Obukhov Similarity (MOS). The model accounts for the decrease in turbulence intensity due to vertical spray stratification that causes reduction in the vertical heat fluxes and decrease in the secondary circulation. Note, the mathematical model does not account for direct impact of the spray on the vertical heat fluxes, but considers only the mechanical effects of the sea spray, therefore, any thermodynamic changes in the system (e.g changes in heat fluxes, temperature distribution) are caused by the mechanical impact of the spray indirectly during the evolution of the hurricane.

In this work we have performed a series of numerical simulations of the idealized TC with different concentrations of sea spray. We have found that the structural characteristics of the storm alter as the sea spray concentration increases, specifically the following changes have been observed: 1) increase in the TC asymmetries, 2) longer maturing time of the hurricane, 3) outward shift in the storm eyewall location, 4) decrease in the vertical extent of reflectivities, 5) reduction in horizontal wind speeds, 6) decrease in the vertical motion and horizontal convergence of the hurricane, and 7) reduction of the total heat flux due to suppressed turbulence.