METEOROLOGICAL ASPECTS OF THE 1992 POLAR SUNRISE EXPERIMENT

A review of synoptic meteorological conditions in the Canadian Arctic was carried out in support of atmospheric chemistry studies during the 1992 Polar Sunrise Experiment. On the basis of the short-term variability in concentrations of several constituents measured at Alert, Northwest Territories, Canada, distinctly different meteorological regimes were identified in the winter and spring. Variability was highest during the winter months, primarily due to the frequent occurrence of episodes of long-range transport of primary pollutants. In the spring the short-term variability in concentrations of many constituents was observed to decrease significantly. The long-range transport events occurred only during the winter regime and accounted for over 40% of the observations made during the 1992 Polar Sunrise Experiment. The dominant transport pathway was across the Arctic Ocean from Eurasia. This pathway was established in the zone between large-surface low-pressure systems typically stretching from Iceland to the Kara Sea and a high-pressure system over the Siberian/Beaufort Arctic. A secondary pathway was observed to bring pollutants with a southerly flow, from the direction of continental North America. The spring of 1992 had lower temperatures, lighter winds, and higher atmospheric pressures than in the previous four years. Four major O-3 depletion episodes were observed in April 1992. Synoptic and back-trajectory analyses showed that these events could not be explained by long-range transport. The recent (1-2 days) history of air parcels associated with these events appeared to be a more significant factor, and evidence of a marine influence was a common feature.