The influence of the summer tropospheric circulation on the observed ozone mixing ratios at a coastal site in the Eastern Mediterranean

Abstract

This study combines surface ozone (O3) measurements at the Finokalia site (Eastern Mediterranean) with backward trajectory modeling results, reanalysis, and satellite data to investigate how the summer tropospheric circulation affects the O3 mixing ratios in the Eastern Mediterranean. The whole dataset covers the summer months (June, July, August) of 2011–2018. Our findings show that north-northeastern flow, known as the Etesians, is a high frequent wind system over the Eastern Mediterranean during the summer period. Under this flow regime, polluted air masses from the continental central and Eastern Europe reach the monitoring site, increasing the O3 mixing ratios of the area. Contrary, western flows carrying maritime air masses from the Mediterranean Sea, though less frequent, have a central role in controlling the annual O3 mixing ratios in the Eastern Mediterranean. Furthermore, the vertical O3 profile analysis over the Finokalia site indicates enhanced O3 mixing ratios in the middle troposphere when northern flows prevail, confirming the significant relationship between the low-level summer atmospheric circulation and the downward transport of O3-rich air masses to the lower troposphere over Finokalia station, Eastern Mediterranean.