Saji Varghese

Contribution of Isoprene Oxidation Products to Marine Aerosol over the North-East Atlantic

Secondary organic aerosol (SOA) formation through isoprene oxidation was investigated with the regional-scale climate model REMOTE. The applied modeling scheme includes a treatment for marine primary organic aerosol emissions, aerosol microphysics, and SOA formation through the gas/particle partitioning of semivolatile, water-soluble oxidation products. The focus was on SOA formation taking place over the North-East Atlantic during a period of high biological activity. Isoprene SOA concentrations were up to ~5 ng over North Atlantic in the base case model runs, and isoprene oxidation made a negligible contribution to the marine organic aerosol (OA) mass. In particular, isoprene SOA did not account for the observed water-soluble organic carbon (WSOC) concentrations over North Atlantic. The performed model calculations, together with results from recent field measurements, imply a missing source of SOA over remote marine areas unless the isoprene oxidation products are considerably less volatile than the current knowledge indicates.

Influence of Marine Aerosols on Cloud Droplet Number Concentration over the North‐East Atlantic

Marine aerosols have a key role in the climate system. They influence the radiative forcings by direct and indirect effects. In this study the influence of marine aerosols over the North‐East Atlantic is determined for January and June 2003 using an advanced regional climate model which has been incorporated with atmospheric chemistry, detailed aerosol dynamics and a cloud droplet activation model. Results reveal dramatic influence of marine aerosols in the formation of cloud droplet number concentration.