Toward a New Chemical Mechanism in WRF/Chem for Direct and Indirect Aerosol Effects: A Focus on the Carbonaceous Aerosols

An updated version of Weather Research and Forecasting/Chemistry model (WRF/Chem) with a new parameterization for the secondary organic aerosol (SOA) production based on the Volatility Basis Set (VBS) is evaluated over Europe in May-June 2003. Results are compared against surface observations issued from the EC/OC 2002-2003 campaign of European Monitoring and Evaluation Program (EMEP). WRF/Chem underestimates the elemental carbon (EC) and the organic aerosol mass (OA) by -7 and -38 %, respectively. The analysis of OA: EC ratio reveals that the under prediction may be mainly explained by a misrepresentation of anthropogenic emissions of carbonaceous aerosols due to the coarse resolution of the inventory. The modeled concentration of OA constituent is nearly constant during the day. The predicted SOA/OA ratio has a value of ∼80 %. The biogenic SOA (BSOA) are 30 % of the total OA mass. Dry deposition velocity of Volatile Organic Compounds (VOC) oxidation products is a source of uncertain in the SOA budget. © Springer Science+Business Media Dordrecht 2014.