The effect of accounting for public holidays on the skills of the atmospheric composition model SILAM v.5.7

Abstract. This study quantifies the impact of emission changes during public holidays on air quality (AQ) and analyses added value accounting for in AQ modelling. Spatial temporal distributions atmospheric concentrations major pollutants (the main focus was NO2, but we also included O3, CO, PM2.5, SO2) were considered at European scale all 2018. Particular attention paid to events with most pronounced continental- or regional-scale impact: Christmas New Year, Easter, May Day vacations, last days Ramadan. The simulations performed chemistry transport model SILAM v.5.7 (System Integrated modeLling Atmospheric coMposition). Three runs made: baseline no treatment holidays, run considering as Sundays, forcing 80 % reduction emissions weekday-sensitive sectors. scaling applied a country basis. predictions compared situ observations collected by Environment Agency. experiment showed that even conservative official has large positive NOx (up 30 bias inhomogeneity holiday days) improves O3 predictions. In many cases, sensitivity suggested greater than level Sundays. An individual consideration different countries may further improve their representation models: specific diurnal pattern emissions, additional due fireworks, driving patterns.