Long Range Transport of Trace Gases Observed on Crete, Greece

The Eastern Mediterranean Area is frequently facing high ozone levels on a regional scale. To a large extent this is due to favourable weather conditions prevailing during summertime seasons. Previous studies primarily addressed urban air quality issues, e.g. in Athens, whereas information about the impact of human activities on the atmospheric composition on remote locations in the Mediterranean still is scarce. Being the southernmost European island and located far away from metropolitan sites Crete offers the possibility to study long-range transports. Air masses arriving at Crete have covered a sigificant part of its tract over the sea, i.e. apart from occasional influences by shipping traffic these air masses remain almost unaffected by emission sources along its trajectory. Here we will report about trace gas measurements carried out at two ground-based sites on Crete during the PAUR-II campaign in May and June 1999: .Nopigia (35°32' N 23°47' E) located at the Gulf of Kissamos at the North coast of Western Crete and Prases (35°22' N 23°51' E) at a mountain ridge in the center of Western Crete at an altitude of 1020 m a.s.l.. Based on ozone and PAN time series obtained simultaneously at both sites we elucidate the different features in terms of long-range transport within the boundary layer.