NUMERICAL-SIMULATION OF WINTER KATABATIC WINDS FROM WEST ANTARCTICA CROSSING SIPLE COAST AND THE ROSS ICE SHELF

Twenty-four-hour numerical simulations of wintertime surface winds und er clear sky conditions over the West Antarctic ice sheet and its vici nity are performed using a hydrostatic, three-dimensional primitive eq uation model. Two initial states are examined: a state of rest, and a prescribed pressure field associated with katabatic winds from West An tarctica propagating across the Ross Ice Shelf. The Antarctic katabati c winds are mainly due to the strong radiative cooling of the ice slop es. The West Antarctic terrain is different from that of East Antarcti ca in two respects: its mean elevation is much lower, and the slope in the interior is steeper than near the margin at Siple Coast. The simu lated surface wind regime reveals confluence zones just inland from th e coast and diffluence zones around the crest of the terrain. The mode l results suggest that the continuation of katabatic winds beyond coas tal confluence zones, which are sustained by cold-air drainage in the interior, has an important impact on airflow over the flat Ross Ice Sh elf adjacent to the Transantarctic Mountains. The prescribed pressure disturbance has little impact on the surface winds in the interior but markedly impacts those over and beyond the gently sloping coastal are as. Discussion of the impact of the surface wind on the polynya northw est of the Ross Ice Shelf is also provided. It is shown that the simul ated surface-wind regime is consistent with the available, mostly surf ace observational data.