Strong gravity flow observed along the slope of Eastern Antarctica

Summary

The winds observed in Adelie Land, Eastern Antarctica, are among the strongest observed anywhere on Earth close to sea level. At Cape Denison, for example, Madigan (1929) measured a mean annual wind speed of 19.1 m s⁻¹. However, little was known until recently about the inland wind conditions, with the exception of short term traverse data collected mostly during summers. Automatic Weather Stations (AWS), reporting over satellites, made year-round data gathering possible over a much larger area, and an array of stations, stretching from Dumont d'Urville to Dome C, some 1080 km inland and at a height of 3280 m, were established in a US-French experiment. Some of the findings are the following:

• 1) The maximum wind speed was found not at the coast, but some distance inland.

• 2) The wind directional constancy was high, even during summer, when the surface inversion is normally destroyed around noon. Only Dome C, where no gravity flow can exist, displayed a large variability in wind direction.

• 3) During winter and night when gravitational acceleration is large, a more downslope component in the wind direction was observed, while during summer and daytime a more cross-slope component is present.

• 4) During summer nights a very shallow surface jet of air flowed down the slopes, the maximum wind speed normally observed was between 80 and 120 m. During daytime, this jet is less pronounced and had a height of about 190 m.

• 5) While the temperature of Dome C was indeed very cold—a minimum of −84.6°C has been observed-the coastal area has a relatively moderate temperature-temperatures below −40°C have never been observed.

• 6) Model calculations and measurements by instrumental plane, which flew between Dome C and the coast, showed fair agreement.