Summer boundary-layer height at the plateau site of Dome C, Antarctica

Measurements of the mean and turbulent structure of the planetary boundary layer by a sodar and a sonic anemometer, and radiative measurements by a radiometer, were carried out in the summer 1999-2000 at the Antarctic plateau station of Dome C during a two-month period. At Dome C strong ground-based inversions dominate for most of the year. However, in spite of the low surface temperatures (between –50 °C and –20 °C), and the surface always covered by snow and ice, a regular daytime boundary layer evolution, similar to that observed at mid-latitudes, was observed during summer time. The mixed layer height generally reaches 200-300 m at 1300-1400 LST in high summer (late December, early January). Late in the summer (end of January – February), as the solar elevation decreases, it reduces to 100-200 m. A comparison between the mixed-layer height estimated from sodar measurements and the one calculated using a mixed-layer growth model shows a rather satisfactory agreement if we assign 0.01-0.02 m s-1 for the subsidence velocity at the top of the mixed layer , and 0.003-0.004 K m-1 for the potential temperature gradient above the mixed layer.