Analysis of Surface Winds at Mawson, Antarctica

An analysis is made of the wind regime at Mawson, Antarctica, to distinguish the meteorological characteristics leading to the gale force winds associated with blizzards as distinct from calm conditions or the relatively moderate and fairly steady surface katabatic winds. Investigation of relationships between the surface and midtropospheric winds over Mawson reveal that strong upper-level winds do not necessarily strengthen the surface wind, reinforcement of which varies with upper wind direction and season. Blizzard, katabatic, and calm wind categories and combinations of these are defined to allow investigation of different characteristics of winds. The importance of considering the katabatic near-surface jet component, which generally strengthens the surface wind, is demonstrated for categories of both weak and strong winds. Features of development in the midtropospheric flow during and 48 h prior to occurrences of blizzard, katabatic, and calm conditions are highlighted. Upper-level forcings associated with blizzard or calm conditions are related to slow-moving high pressure cells downstream. Similarities in forcing mechanisms of calm and katabatic periods suggest a relationship with the efficient drainage of low-level air, although there is evidence that upper-level opposition to the surface flow produces calm conditions.