Evaluation of SO<sub>2</sub>, SO<sub>4</sub><sup>2−</sup> and an updated SO<sub>2</sub> dry deposition parameterization in the United Kingdom Earth System Model

Abstract. In this study we evaluate simulated surface SO2 and sulfate (SO42-) concentrations from the United Kingdom Earth System Model (UKESM1) against observations ground-based measurement networks in USA Europe for period 1987–2014. We find that UKESM1 captures historical trend decreasing of atmospheric SO42- both over However, polluted regions eastern Europe, over-predicts by a factor 3 while under-predicting 25 %–35 %. cleaner western USA, model factors 12 1.5 respectively. UKESM1’s bias is variable according to region season. also total column Ozone Monitoring Instrument (OMI) using an updated data product. This comparison provides information about model's global performance, finding much globe, including large source India, China, as well outflow regions. Finally, assess impact more realistic treatment dry deposition parameterization. change increases land ocean surfaces, thus reducing loading SO42-. with satellite observations, modified parameterization reduces over-prediction SO2. Relative are reduced, fluxes increase.