[1] This study presents a novel approach to develop a combined organic-inorganic sub-micron sea-spray source function for inclusion in large-scale models. It requires wind speed and surface ocean chlorophyll-a concentration as input parameters. The combined organic-inorganic source function is implemented in the REMOTE regional climate model and sea-spray fields are predicted with particular focus on the North East Atlantic. The model predictions using the new source functions compare well with observations of total sea-spray mass and organic carbon fraction in sea-spray aerosol. During winter (periods of low oceanic biological activity), sea-salt dominates the sea-spray mass while in summer (when biological activity is high), water soluble organic carbon contributes between 60-90% of the submicron sea-spray mass.

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Abstract. This paper summarizes an evaluation of model simulations with a regional scale atmospheric climatechemistry/aerosol model called REMOTE, which has been extended by a microphysical aerosol module. Model results over Europe are presented and compared with available measurements in surface air focusing on the European distribution and variability of primary and secondary aerosols. Additionally, model results obtained with detailed aerosol microphysics are compared to those based on an aerosol bulk mass approach revealing the impact of dry deposition fluxes on atmospheric burden concentration. An improved determination of elevated ozone and sulfate concentrations could be achieved by considering a diurnal cycle in the anthropogenic emission fluxes. Deviation between modelled and measured organic carbon concentrations can be mainly explained by missing formation of secondary organic aerosols and deficiencies in emission data. Changing residential heating practices in Europe, where the use of wood is no longer restricted to rural areas, need to be considered in emission inventories as well as vegetation fire emissions which present a dominant source of organic carbon.

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 m −3 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.

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