The impact of temperature changes on summer time ozone and its precursors in the Eastern Mediterranean

Abstract. Changes in temperature due to variability in meteorology and climate change are expected to significantly impact atmospheric composition. The Mediterranean is a climate sensitive region and includes megacities like Istanbul and large urban agglomerations such as Athens. The effect of temperature changes on gaseous air pollutant levels and the atmospheric processes that are controlling them in the Eastern Mediterranean are here investigated. The WRF/CMAQ mesoscale modeling system is used, coupled with the MEGAN model for the processing of biogenic volatile organic compound emissions. A set of temperature perturbations (spanning from 1 to 5 K) is applied on a base case simulation corresponding to July 2004. The results indicate that the Eastern Mediterranean basin acts as a reservoir of pollutants and their precursor emissions from large urban agglomerations. During summer, chemistry is a major sink at these urban areas near the surface, and a minor contributor at downwind areas. On average, the atmospheric processes are more effective within the first 1000 m above ground. Temperature increases lead to increases in biogenic emissions by 9±3% K⁻¹. Ozone mixing ratios increase almost linearly with the increases in ambient temperatures by 1±0.1 ppb O₃ K⁻¹ for all studied urban and receptor stations except for Istanbul, where a 0.4±0.1 ppb O₃ K⁻¹ increase is calculated, which is about half of the domain-averaged increase of 0.9±0.1 ppb O₃ K⁻¹. The computed changes in atmospheric processes are also linearly related with temperature changes.