Effects of two different biogenic emission models on modelled ozone and aerosol concentrations in Europe
Abstract. Biogenic volatile organic compound (BVOC) emissions are one of the essential inputs for chemical transport models (CTMs), but their estimates are associated with large uncertainties leading to significant influences on air quality modelling. This study aims at investigating the effects of using different BVOC emission models on the performance of a CTM in simulating secondary pollutants, i.e. ozone, organic and inorganic aerosols. The European air quality was simulated for the year 2011 by the regional air quality model Comprehensive Air Quality Model with Extensions (CAMx) version 6.3, using BVOC emissions calculated by two emission models: the Paul Scherrer Institute (PSI) model and the Model of Emissions of Gases and Aerosol from Nature (MEGAN) v2.1. Comparison of isoprene and monoterpene emissions from both models showed large differences in their general amounts as well as their spatial distribution both in summer and winter. MEGAN produced more isoprene emissions by a factor of 3 while the PSI model generated three times of monoterpene emissions in summer, while there was negligible difference (~ 4 %) in sesquiterpene emissions associated with the two models. Despite the large differences in isoprene emissions (i.e. 3-fold), the resulting impact in predicted summer-time ozone proved to be minor ( 60 ppb). A much larger effect of the different BVOC emissions was found for the secondary organic aerosol (SOA) concentrations. The higher monoterpene emissions (a factor of ~ 3) by the PSI model led to higher SOA by ~ 110 % on average in summer, compared to MEGAN, improving substantially the model performance for organic aerosol (OA): the mean bias between modelled and measured OA at 8 Aerodyne aerosol chemical speciation monitor (ACSM)/Aerodyne aerosol mass spectrometer (AMS) measurement stations was reduced by 21 %–83 % in rural/remote stations. Effects on inorganic aerosols (particulate nitrate, sulphate, and ammonia) were relatively smaller (