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

Measurements of the mean and turbulent structure of the planetary boundary layer using a sodar and a sonic anemometer, and radiative measurements using a radiometer, were carried out in the summer of 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 and -20 degrees 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 summertime. 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 to February), as the solar elevation decreases, it reduces to 100-200 m. A comparison between the mixed-layer height estimated from sodar measurements and that calculated using a mixed-layer growth model shows a rather satisfactory agreement if we assign a value of 0.01-0.02 m s(-1) to the subsidence velocity at the top of the mixed layer, and a value of 0.003-0.004 K m(-1) to the potential temperature gradient above the mixed layer.