Trajectory Analysis of High-Alpine Air Pollution Data

The EUROTRAC subproject ALPTRAC (High Alpine Aerosol and Snow Chemistry Study) is devoted to the investigation of air and snow pollution at high Alpine sites. The aerosol surface concentration is continuously recorded at Jungfraujoch (3450 m a.s.1., 7° 59’E, 46° 32’N) in the Swiss Alps and Sonnblick (3106 m a.s.1, 12° 57’E,47° 03’N) in the Austrian Alps with a time resolution of 30 min with an epiphaniometer (Gäggeler et al., 1989; Baltensperger, et al. 1991). The measurements showed a pronounced seasonal cycle with mean summer concentrations more than one order of magnitude higher than mean winter concentrations, and the occurrence of episodes with especially high or low concentrations (Seibert et al., 1993). While the seasonal cycle is mainly to be explained by the atmospheric stability, the short-term variations are caused by synoptic-scale transports. These have been investigated using isobaric back trajectories at 700 hPa with a length of 72 h, computed twice daily for a period of three years (July 1990 - June 1993). Due to technical problems at Sonnblick, only 925 trajectories were available for the analysis; most of the missing data fall on winter.