Impact of Sea Spray on Hurricane Simulations

It has long been recognized that sea spray may considerably impact sensible and latent heat flux at the ocean surface, and thus change the effective transfer coefficient for enthalpy. However, the extent to which sea spray can affect the surface enthalpy flux (hence its effective transfer coefficient) has not been determined due to the lack of understanding of the process and relevant data. It remains unclear how the droplet-produced latent heat flux should be partitioned to offset the sensible heat flux; this issue critically defines the extent to which the enthalpy flux can be increased due to the spray droplet latent heat release. Even though significant challenges remain, progress has been made in sea spray parameterizations. In this study, latest improved sea spray parameterizations have been implemented in the Navy's Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS). A high-resolution version of COAMPS is used to simulate the development of Katrina 2007 with different sea spray parameterizations. The boundary layer budgets of momentum, heat, and moisture and turbulence kinetic energy are computed to understand the processes impacted by sea spray. It has been found that sea spray increases the ratio of the turbulence enthalpy transfer coefficient and the drag at the surface. The inclusion of the parameterizations enhances the hurricane intensity since more moisture is supplied to the boundary layer. On the other hand, the evaporative cooling generated by the spray stabilizes the boundary layer, which tends to slow down the hurricane intensification. The budget analysis provides further evidence that the boundary layer process is sensitive to sea spray.