Numerical study of natural sea salt aerosol and its radiative effects on climate and sea surface temperature over East Asia

A regional climate model, RIEMS-POM, was used to study the direct radiative forcing (DRF) of sea salt on precipitation, sea surface temperature (SST) and summer circulation over East Asia with aerosol dataset from GOCART. The simulations predicted negative DRFs of −0.87 W m−2 at the surface and −1.40 W m−2 at the top of the atmosphere by sea salt. Results from the simulations suggest the forcing of sea salt produces a slight positive temperature anomaly and a reduction in precipitation over Southern China, accompanied by an opposite trend north of 40°N in Northern and Northeastern China. The tendency of wetting in North and drying in South by sea salt was mainly determined by the wind field, the vertical motion, as well as the local evaporation anomalies. The impacts of sea salt on SST suggest that the net surface shortwave radiative flux and the changes in convective cloud are important in forming the decreased SST throughout the year, while the northward oceanic heat transport anomaly and the other heat flux anomalies contribute relatively smaller. The feature by sea salt on SST imposes an extra force from the atmosphere to the ocean. The sea salt could also diminish the land-sea temperature contrast (LSTC) in summer and therefore the climatological summer circulation over East Asia, leading to reduced precipitation in Southern China. All these climatic feedbacks, such as LSTC and precipitation anomaly, will be attenuated when the SST is fixed.