US EPA

602210 

Journal Article 

Influence of air mass long-range transport on ozone concentration at Preila site (Lithuania) 

Bycenkiene, S; Girgzdiene, R 

2006 

46 

2 

251-259 

Ground-level ozone measurement data and air mass backward trajectories were used to determine the influence of the long-range transport on the ozone level. A cluster algorithm was implemented to analyse the backward trajectories of air masses arriving from North America to the Preila site located on the eastern coast of the Baltic Sea. The 10-day air mass backward trajectories were clustered and grouped according to season, travelled way, and height over the surface before arrival. Dominant air mass transport from North America was identified in the late autumn-winter (up to 69% of total events). The air masses from the "unpolluted" cluster in all seasons, except summertime, showed slightly higher ozone concentrations than those from the "polluted" cluster. The highest ozone concentration of 78+/-12 mu g m/sup -3/ was found in air masses that travelled at the >2 km height above the surface from the "unpolluted" cluster during a winter period. It was established that the transport of air masses from North America was mainly associated with cyclones (65%). The change in the ozone level at the Preila site was up to +/-10 mu g m/sup -3 / during the episodes when the transport of air masses from North America was detected