Climatology of the three coastal Antarctic stations Dumont d'Urville, Neumayer, and Halley

Long term air and snowfall chemistry measurements have been performed at the three coastal Antarctic stations Dumont d'Urville (66 degrees 40'S, 140 degrees 1'E), Neumayer (70 degrees 39'S, 8 degrees 15'W), and Halley (75 degrees 35'S, 26 degrees 19'W). The results have to be interpreted and compared with respect to the regional meteorological conditions. In this study the 3-hourly synoptic surface observations taken at the three stations between 1991 and 1995, as well as the daily upper air soundings from 1993, are analyzed to describe the aspects of station climatologies relevant for the air and snowfall chemistry measurements discussed in the papers of this special section. Although the three stations are comparable, being situated close to the coastline of Antarctica, the meteorological conditions differ. While at Dumont d'Urville katabatic winds cause predominant strong and relatively dry surface winds from the interior of Antarctica, Neumayer and Halley are frequently influenced by easterly winds associated mostly with eastward moving cyclones, From April through October the wind field above 5 km is governed by a circumpolar vortex with westerly winds increasing in intensity with height. Dumont d'Urville represents a station at the edge of this vortex with extreme stratospheric wind velocities up to above 50 m s(-1). Neumayer and Halley are mostly situated within the vortex and isolated from air masses advecting from lower latitudes into the upper troposphere and lower stratosphere during the Austral winter.