Analysis of surface winds at Mawson, Antarctica

An analysis is made of the wind regime at Mawson, Antarctica, to distinguis h the meteorological characteristics leading to the gale force winds associ ated with blizzards as distinct from calm conditions or the relatively mode rate and fairly steady surface katabatic winds. Investigation of relationsh ips between the surface and midtropospheric winds over Mawson reveal that s trong upper-level winds do not necessarily strengthen the surface wind, rei nforcement of which varies with upper wind direction and season. Blizzard, katabatic, and calm wind categories and combinations of these are defined t o allow investigation of different characteristics of winds. The importance of considering the katabatic near-surface jet component, which generally s trengthens the surface wind, is demonstrated for categories of both weak an d strong winds. Features of development in the midtropospheric flow during and 48 h prior to occurrences of blizzard, katabatic, and calm conditions a re highlighted. Upper-level forcings associated with blizzard or calm condi tions are related to slow-moving high pressure cells downstream. Similariti es in forcing mechanisms of calm and katabatic periods suggest a relationsh ip with the efficient drainage of low-level air, although there is evidence that upper-level opposition to the surface flow produces calm conditions.