| Summary: | Profile mast, tethersonde and radiosonde measurements are used to describe the structure and dynamics of the summertime atmospheric boundary layer over the slightly sloping snow surface at Kohnen base (75°00'S, 0°04'E, 2892 m above sea level), located on the interior plateau of East Antarctica. During a 4-day clear-sky period at the end of summer, we found a shallow but dynamic boundary layer. Net radiation contributed between -40 and +35 W m-2 to the surface energy balance and was negative on average; the sensible and latent heat fluxes contributed less than 10 W m-2 and 1 W m-2, respectively; the subsurface heat flux mostly counteracted the radiative flux. Owing to nighttime radiative cooling at the surface an increasingly deep stable layer formed with a temperature deficit of over 12 K. Within this layer we observed a katabatically driven low-level jet which increased in altitude from 20 to 70 m during the night and persisted up to noon. By that time a shallow mixed layer was deepening and warming underneath the stable layer. The mixed layer obtained a maximum depth of 70 m halfway through the afternoon. During the experiment the ABL was near saturation. The observations were used to validate a one-dimensional atmospheric boundary layer model.
|
|---|