Air Parcel Trajectories and Snowfall Related to Five Deep Drilling Locations in Antarctica Based on the ERA-15 Dataset

Abstract

Five-day backward air parcel trajectories are used to define potential moisture sources of snow falling at five Antarctic deep drilling locations: Byrd, DML05, Dome C, Dome F, and Vostok. The trajectory calculations are based on European Centre for Medium-Range Weather Forecasts reanalysis data, ERA-15 (1979?93). Based on model precipitation, a distinction is made between cases with and without snowfall at the point of arrival. ERA-15 precipitation is in reasonable agreement with measured accumulation at Byrd, but seriously underestimates the amount of precipitation on the East Antarctic ice sheet. The trajectories show that the oceans closest to the site contribute the most moisture. The latitude band contributing most (?30% of the total annual precipitation) is 50°?60°S, that is, the area just north of the sea-ice edge. The calculated trajectories show seasonal dependency, resulting in a seasonal cycle in the moisture sources, which is further enhanced by a seasonal cycle in the amount of precipitation. The interannual variability of the source regions is of the order of 3° latitude. At DML05, a significant northward moving moisture source region is detected, while at Dome C a significant southward movement is observed.