Assessing the impact of climate change on summertime tropospheric ozone in the Eastern Mediterranean: Insights from meteorological and air quality modeling

Abstract

This study evaluates the impact of climate change on tropospheric ozone (O₃) concentrations in the Eastern Mediterranean using the Weather Research and Forecasting (WRF) and the Community Multiscale Air Quality (CMAQ) models. Simulations were conducted for a historical period (2012) and a future projection (2053) under SSP2-4.5 and SSP5-8.5 scenarios. Anthropogenic emissions were sourced from the EMEP/EEA inventory, while biogenic emissions were calculated using the MEGAN model. Model performance evaluations yielded R² (RMSE) values of 0.71–0.85 (3.33–4.9) for WRF and 0.58 (8.35) for CMAQ, indicating reasonable predictive accuracy. Under SSP5-8.5 (SSP2-4.5), the WRF model projects an average summertime temperature increase of 1.6 °C (1.2 °C) and a significant decline in precipitation across the Eastern Mediterranean. Air quality simulations show a regional increase in summertime O₃ concentrations by 3.5 ppb (3.0 ppb) under SSP5-8.5 (SSP2-4.5), with the most pronounced increases occurring in the southeast. Conversely, a significant reduction in O₃ concentrations is observed over the Marmara Sea and parts of Istanbul in both scenarios. This reduction is attributed to climate-induced processes, including accelerated O₃ photolysis in moist conditions and enhanced O₃ consumption by NO_x in the NO_x-saturated regime of the Marmara Sea region. Additionally, analyses reveal a significant increase in O₃ levels in Istanbul under SSP5-8.5, while Bursa shows notable increases under both scenarios. These findings underscore the need for targeted emission control measures to mitigate future O₃ pollution in the region.