Sea salt aerosol production via sublimating wind-blown saline snow particles over sea-ice: parameterizations and relevant micro-physical mechanisms

Blowing snow over sea-ice has been proposed as a direct source of sea salt aerosol (SSA) (Yang et al., 2008). In this study, based on data (e.g. snow salinity, blowing snow and aerosol particle measurements) collected in the Weddell Sea sea-ice zone (SIZ) during a winter cruise, we perform a comprehensive model-data comparison with the aim of validating the parameterizations and investigating possible physical mechanisms involved in SSA production from blowing snow. A global chemistry transport model, p-TOMCAT, is used to examine the model sensitivity to key parameters involved, namely blowing snow size distribution, snow salinity, evaporation function, snow age, surface wind speed, relative humidity, air temperature and ratio of SSA formed per snow particle. As proposed in Yang et al.'s parameterizations, SSA mass flux is proportional to bulk sublimation flux of blowing snow and snow salinity. To convert bulk sublimation flux to SSA size distribution, requires (1) evaporation function for snow particles, (2) blowing snow size distribution, (2) snow salinity, and (4) ratio of SSA formed per snow particle. The best model-cruise aerosol data agreement (in size range of 0.4–10 µm) indicates two possible micro-physical processes that could be associated with SSA production from blowing snow. The first one is under the assumptions that one SSA is formed per snow particle after sublimation, and snow particle evaporation is controlled by the curvature effect or the so-called air ventilation effect. The second mechanism allows multiple SSAs to form per snow particle and assumes snow particle evaporation is controlled by the moisture gradient between the surface of the particle and the ambient air. At a production ratio of ~10, it is possible to reproduce the observations. Although both mechanisms generate very similar results (to match the observations), they correspond to completely different micro-physical processes and show quite different SSA size spectra, mainly in ultra-fine and coarse size modes. However, due to the lack of relevant data, we could not, so far, conclude confidently which one is more realistic, highlighting the necessity of further investigation