Mesoscale Meteorological Conditions in Dronning Maud Land, Antarctica, during Summer: A Qualitative Analysis of Forcing Mechanisms

Abstract

Detailed concurrent summer observations of surface meteorological variables, high-resolution boundary layer profiles, and upper-air profiles were carried in the intermediate region between the high plateau and the coast in Dronning Maud Land, Antarctica, a region that includes several blue ice areas. The main goal is to find out to what extent the flow is influenced by 1) slope-inversion pressure gradients (katabatic force), 2) synoptic pressure gradients (geostrophic wind), and 3) thermal gradients (thermal wind), and how this compares with the situation near the coast. Both synoptic and katabatic forcings generally induce easterly winds in the boundary layer, with a clear diurnal cycle in their relative importance. Westerly surface winds occur less often than at nearby coastal stations Halley and Neumayer, indicating that the influence of synoptic and thermal effects decreases toward the interior of Antarctica. Hence, katabatic forcing dominates, in particular during clear-sky conditions. Under weak synoptic forcing, the boundary layer over the main blue ice area is susceptible to local-scale circulations, which produces noneasterly winds at the surface. This result is caused mainly by reduced cooling over blue ice, which renders the katabatic force weak or absent, and by the typical topographic setting.