| Popis: |
Aerosol concentration and size parameters have been measured at several sites in the western hemisphere Arctic. A diurnal variation in concentration of the small size fraction of the aerosol (Aitken nuclei) is a frequent occurrence over both ice covered and vegetated Arctic areas on sunlit days in summer and winter. The midday increase in small particle concentration is confined to the thin, near surface, mixing layer. The concentration of the particles large enough to scatter visible light or be impacted inertially, varies by a large amount over short time periods, but does not systematically vary with time of day. The maximum concentration of this size range of particles was measured at the surface several tens of hours after warmer air was advected over the sampling site when the surface was snow covered. Summer experiments on the ice cap of southern Greenland show minimum concentration of all fractions of the aerosol size spectrum when a low pressure system south of Greenland caused moist upslope flow and precipitation to occur. The concentration of both large and small size particles increases as the low tracks eastward, and the maximum concentration of all particles, including large, sharp edged silicates occurs in downslope flow under clearing skies, as high pressure begins to be established over Greenland. |
