Tropopause Folds Over the Eastern Mediterranean and the Middle East in EMAC Simulations: Implications for Summertime Tropospheric Ozone

A 35 year climatological analysis (1979–2013) of tropopause fold frequency has been performed over the eastern Mediterranean and the Middle East, focusing on the implications for tropospheric ozone. The analysis is based on simulations with the EMAC (ECHAM5-MESSy) atmospheric chemistry climate model using a T42L90MA resolution, nudged tropospheric meteorology towards ERA-Interim reanalysis data and a tracer for stratospheric ozone (O3s). We implement a 3-D labeling algorithm, in order to detect tropopause folding events in EMAC simulations as areas of multiple crossings of the dynamical tropopause. A clear hot spot of tropopause folds occurs over the broader eastern Mediterranean and Middle East region during the summer season. A significant contribution of tropopause folds to the summertime pool of high tropospheric ozone over the eastern Mediterranean is identified during the selected fold events. Finally, a year-to-year analysis indicates a significant positive correlation between the observed near surface ozone and EMAC simulated middle/lower tropospheric ozone over the eastern Mediterranean.