The Impact of Dust Radiative Forcing on the Ocean Surface Energy Budget

This study investigates the impact of the dust radiative forcing on the energy budget, focusing particularly on the surface energy fluxes over ocean. The model integrated for a single month but will be extended to a full summer season in the near future. Two numerical experiments, identical in all respects except for the simulation of dust-radiative effects (ON for dust-radiation active, OFF for dust-radiation inactive), were conducted. The initial and boundary conditions for the atmosphere and ocean were taken from CFSv2 (Climate Forecast System Version 2) 6-hourly products and HYCOM (Hybrid Coordinate Ocean Model) reanalysis data, respectively.

Monthly means for several fields were computed, including net downward shortwave and longwave fluxes at the surface, latent heat and sensible heat fluxes at the surface, 2-m temperature and moisture, 10-m wind, sea surface temperature (SST), precipitation and integrated cloud mass, for both experiments. The impact of the dust radiative forcing was evident in differences between the two experiments, including a northward shift in clouds and rainfall, a decrease in the surface net downward shortwave radiation, an increase in the surface net downward longwave radiation, and an increase of 2-m temperature in ON compared to OFF. The most interesting impact of the dust-radiative forcing is a decrease in the surface latent heat flux in the ON simulation relative to OFF. The latent heat flux decrease present off the West African coast is caused by a negative net energy flux at the surface. However, the decrease seen near the tropics is due to a decrease in surface winds. It is surprising to note that monthly average SSTs are impacted very little by dust-radiative effects during this one-month simulation even though the net downward energy flux at the surface decreases due to dust in the ON experiment. The results from this preliminary study are rather interesting and more analysis will be performed.