AIR-MASS TRAJECTORIES TO SUMMIT, GREENLAND - A 44-YEAR CLIMATOLOGY AND SOME EPISODIC EVENTS

The seasonal variation in atmospheric transport patterns to Summit, Gr eenland, is examined using a 44-year record of daily, 10-day, isobaric back trajectories at the 500-hPa level. Over 24,000 modeled trajector ies are aggregated into distinct patterns using cluster analysis. Ten- day trajectories reaching Summit are longest during winter, with 67% e xtending upwind (westward) as far back as Asia or Europe. Trajectories are shortest during summer, with 46% having 10-day origins over North America. During all seasons a small percentage (3-7%) of trajectories originate in west Asia/Europe and follow a meridional path over the A rctic Ocean before approaching: Summit from the northwest. Trajectorie s at the 700-hPa level tend to be shorter than at 500 hPa, with many o f the 700-hPa trajectories from North America tracking over the North Atlantic and approaching Summit from the south. The long-range transpo rt climatology for Summit is similar to a year-round climatology prepa red for Dye 3, located 900 lan to the south [Davidson et al., 1993b]. An analysis of several aerosol species measured at Summit during summe r 1994 reveals examples of the usefulness and also the limitations of using long-range air trajectories to interpret chemical data.