Foehn winds in the McMurdo Dry Valleys of Antarctica

Foehn winds play a major role in the climate of the McMurdo Dry Valleys, as they often warm the valleys to above-freezing conditions in the summer, and are the dominant wind regime during the winter. Here we investigate foehn winds in the McMurdo Dry Valleys using automatic weather station (AWS) observations, infrared satellite imagery, and high-resolution model simulations from the Antarctic Mesoscale Prediction System (AMPS). A case study of a prominent foehn wind event from May 2007 illustrates the dynamics and physical processes involved in the generation of foehn winds. Strong winds and warming in the valleys primarily result from mountain waves and windstorms down the valley walls, rather than from along-valley drainage flow. The structure of mountain waves in regards to conditions at various AWS sites is discussed. Composite synoptic-scale conditions for foehn and non-foehn wind events over a 2-year period are presented, and show that foehn events in the McMurdo Dry Valleys are related to the large-scale Antarctic continental wind regime. Insights are given into the impacts that large-scale climate variability patterns (e.g. SAM) have on conditions in the McMurdo Dry Valleys.