Katabatic winds are prevalent boundary-layer features over Antarctica arising from radiative cooling of the sloping ice fields. The terrain configuration of the continent results in a low-level radial drainage of cold air from the gently sloping interior plateau to the steep coastal escarpment. The persistence of the katabatic wind regime implies that continental-scale subsidence into the boundary layer over Antarctica is required from mass continuity considerations. The resulting meridional circulation provides a direct link between the katabatic wind regime and the free atmosphere. A number of numerical experiments utilising both axisymmetric and three-dimensional models have been completed in order to investigate the coupling between the Antarctic katabatic wind field and resulting tropospheric motions. Axisymmetric model simulations indicate that an upper-level cyclonic vortex rapidly forms in response to the drainage circulations. Adverse horizontal pressure gradients associated with the circumpolar current in the free atmosphere act to check the drainage flow and hence the katabatic wind regime decays to a fraction of its original intensity over a time-scale of ten days or so. Three-dimensional model simulations suggest that the departures from axisymmetry result in longitudinal variations in the intensity of the katabatic wind-induced vortex motions. The strongest simulated upper-level winds are found over the coastal slopes of east Antarctica. Automatic weather station data reveal that katabatic winds are able to persist at Terra Nova Bay in spite of adverse low-level horizontal pressure gradients over the offshore oceanic regions. Dramatic differences in the forcing of surface winds over the continental ice slopes and the offshore environment are evident. Katabatic winds are shown to be sensitive to the radiative cooling of the local terrain, responding to the annual cycle of solar forcing.
Thomas R. Parish (Tue,) studied this question.