Estimating Direct Effects of Secondary Organic Aerosol Over Europe Using COSMO-ART

COSMO-ART is a recently developed regional model that couples meteorological and air quality processes online. It allows for a consistent chemical forecasting since it avoids temporal and spatial interpolation steps. Additionally, it enables the simulation of feedbacks between chemistry, aerosols and meteorology. Towards this direction, COSMO-ART has already incorporated the direct radiative forcing of aerosol processes. In the framework of this study, COSMO-ART is modified to include the volatility basis set (VBS) treatment of secondary organic aerosol (SOA) chemistry. The VBS approach assumes gas-to-particle partitioning of all (thousands) organics grouped by their saturation concentration and calculates their formation and chemical evolution (aging) into the atmosphere. COSMO-ART simulations are performed for May 2008 covering the greater European area with a horizontal resolution of 14 km and a vertical extend up to 20 km. Results are compared to PMCAMx predictions and are evaluated against EUCAARI measurements. Sensitivity simulations reveal the effectiveness of the VBS approach against a traditional SOA module and the fraction of anthropogenic SOA. Additional simulations excluding organic chemistry, aim at identifying the SOA effect on radiation and atmospheric temperature. An average radiative reduction is predicted over Europe, linked to a moderate temperature decrease.