Accelerated Estimation of Sea Spray-Mediated Heat Flux Using Gaussian Quadrature

Sea spray-mediated heat flux plays an important role in air-sea heat transfer. Heat flux integrated over droplet size spectrum can well simulate total heat flux induced by sea spray droplets. Previously, a fast algorithm of spray-flux assuming single-radius droplets (A15) was widely used since the full-size spectrum integral is computationally expensive. Based on the Gaussian Quadrature (GQ) method, a new fast algorithm (SPRAY-GQ) of sea spray-mediated heat flux is derived. The performance of SPRAY-GQ is evaluated by comparing heat fluxes with those estimated from the widely-used A15. The new algorithm shows a better agreement with the original spectrum integral. To further evaluate the numerical errors of A15 and SPRAY-GQ, the two algorithms are implemented into a coupled CFSv2.0-WW3 system, and a series of 56-day simulations in summer and winter are conducted and compared. The comparisons with satellite measurements and reanalysis data show that the SPRAY-GQ algorithm could lead to more reasonable simulation than the A15 algorithm by modifying air-sea heat flux. For experiments based on SPRAY-GQ, the sea surface temperature at mid-high latitudes of both hemispheres, particularly in summer, is significantly improved compared with the experiments based on A15. The simulation of 10-m wind speed and significant wave height at mid-low latitudes of the Northern Hemisphere after the first two weeks is improved as well. These improvements are due to the reduced numerical errors. The computational time of SPRAY-GQ is about the same as that of A15. Therefore, the newly-developed SPRAY-GQ algorithm has a potential to be used for calculation of spray-mediated heat flux in coupled models.