Decadal regional air quality simulations over Europe in present climate: near surface ozone sensitivity to external meteorological forcing

Abstract

Abstract. Regional air quality decadal simulations were carried out using the air quality model CAMx driven off-line by the regional climate model RegCM3 for the time slice 1991–2000 using two different datasets of external meteorological forcing to constrain RegCM3: the ERA40 global atmospheric reanalysis dataset and the output from the GCM ECHAM5. The focus of this work is to compare the perfect lateral boundary conditions experiment with the GCM driven control experiment and to investigate how this external meteorological forcing affects near surface ozone. The different RegCM3 meteorological forcings resulted in changes of near surface ozone over Europe ranging between ±5 ppb for winter and summer, while all model parameterizations and anthropogenic emissions remained unchanged. Changes in near surface ozone are induced by changes in meteorological fields and biogenic emissions, which are on-line calculated and meteorology-dependent. The model simulations suggest that the change in solar radiation is the factor that mostly modulates the ozone changes in summer. During winter season it is found that the induced changes in NOx explain about 40% of the ozone variability. The meteorological induced changes in biogenic emissions are quite low for winter with rather small impact on ozone while they are more temperature than radiation dependent. Using multiple regression analysis to associate the changes in near surface ozone with the respective changes in selected meteorological parameters and ozone precursors, an explained variance of 70% in summer and 60% in winter is reproduced.