AEROSOL TRANSPORT TO THE HIGH ALPINE SITES JUNGFRAUJOCH (3454-M-ASL) AND COLLE-GNIFETTI (4452-M-ASL)

Atmospheric transport processes, relevant to high Alpine sites, were d educed from 2 sets of aerosol records: a 9-year record from the Jungfr aujoch (3454 m) on the northern side of the Swiss Alps and a 2.5-year record from Colle Gnifetti (4452 m) on the southern side. A classifica tion scheme for synoptic weather types was applied to separate the aer osol data into groups corresponding to different atmospheric transport conditions. For both sites, vertical aerosol transport by thermally d riven convection, acting between late spring and late summer, was foun d to be the dominant transport process. In summer, the thermally-drive n aerosol transport to both sites caused an increase of the seasonally averaged aerosol concentration between 0800 and 1800 local standard t ime by a factor of two. Under anticyclonic conditions, when subsidence on a synoptic scale is present, the thermally driven aerosol transpor t is most pronounced. Therefore, the aerosol determining thermal trans port takes place within a synoptic scale vertical motion of opposite d irection. Under cyclonic conditions, when lifting on a synoptic scale is present, the thermally driven aerosol transport is nearly absent. I n winter, thermally driven convection does not contribute to the aeros ol concentrations at both sites. Nevertheless, also in winter statisti cally significant differences in aerosol concentration were found betw een cyclonic and anticyclonic weather conditions, which can be attribu ted to the vertical transport acting on the synoptic scale. These diff erences in aerosol concentration were small compared to the correspond ing differences in summer. Within the weather types, which are dominat ed by horizontal advection in the Alpine region, the aerosol concentra tions are more difficult to interpret with respect to the effective tr ansport process.