Richard Walker

University of Wyoming

Dept of Atmospheric Science

MS candidate

Diagnosis of Synoptic-Scale Influences on the Antarctic Wind Regime Using

Observational and Numerical Methods

The Antarctic boundary layer is characterized by intense winds that have often been interpreted as purely katabatic in nature due to the longwave radiation loss and attendant drainage from the elevated continental interior, the topography of the ice sheet, and the extreme directional constancy values approaching 1.0. Along with this, the Antarctic coast is frequented by synoptic activity due to strong temperature gradients that exist between the ice-covered continent and the relatively warm oceans to the north.

This research looked at the role that transient synoptic-scale cyclones play on the near-surface wind regime of the east Antarctic via two analysis methods. First, an early 20^th century two-year observational dataset resulting from an Antarctic expedition was examined at the coastal station Cape Denison (67.1ºS, 142.7ºE) and from the strong negative correlation between pressure and wind speed it was concluded that the wind regime has a significant synoptically-forced component to the wind regime, and is not entirely katabatic. Second, to validate the aforementioned conclusion, numerical simulations of the east Antarctic were ran utilizing polar version 3.6 of the fifth-generation PSU-NCAR Mesoscale Model for the month of April 2002 where the density of synoptic-scale cyclones is relatively high. Components of the pressure gradient force (PGF) were output to determine the relative roles of both synoptic and katabatic forcing. It was concluded that the synoptic component of the PGF has a magnitude equal to and exceeding the katabatic component of the PGF during episodes of synoptic activity, giving rise to the near-surface wind regime exhibiting a ‘quasi-katabatic’ behavior.