Antarctic surface winds: synoptic-topographic interactions

Li Huilan

University of Wyoming

MS thesis defense

Observations from coastal stations have shown that the direction of the Antarctic surface wind regime undergoes little seasonal variations. The low-level winds over the Antarctic continent are highly persistent and are directed downslope toward the coast, deflected to the left of the fall line by the Coriolis force. Antarctic surface winds have traditionally been interpreted as of katabatic origin. The intense baroclinic nature of the Antarctic continental coastal margin, however, implies that strong cyclonic forcing is present. In addition, topographic influences on the surface wind regime must be operating to account for the directional persistence of the wind. Furthermore, the summertime surface wind regime is highly persistent despite having little katabatic influence. This suggests that the Antarctic surface wind regime is more complicated than previously thought.

Results from numerical simulations indicate that a wind regime similar to the observed wind field could be produced by the blocking influence of the Antarctic topography on approaching synoptic processes. The impingement of synoptic processes on the Antarctic periphery results in an accumulation of air mass against the Antarctic barrier and a significant adjustment of the pressure field. A downslope pressure gradient becomes established, with higher pressure over the sloping terrain and lower pressure over the ocean, inducing the production of the barrier winds. The adjustment of the pressure field produces low-level flows that are similar to the katabatic winds. This implies that the role of the katabatic effect on the Antarctic surface winds may be exaggerated, and that such barrier effects could be critical in explaining the observed Antarctic surface wind characteristics.