Antarctic winds


Antarctica has impressive surface winds. They are unusual because they are related in a simple way to topography. The map shows a 1979-2014 climatology of surface winds derived from ECMWF’s ERA-interim.  In the interior of the continent, the combination of a strong temperature inversion (radiative cooling of the ice cap under clear skies) and sloping terrain generates an “inversion wind”[1]. The cold bottom layer simply slips downhill. Large-scale motion is affected by the earth’s rotation, deflecting winds to the left. Near the coast, steeper gradients generate extreme “katabatic” winds, especially when channelled into straits or valleys.

The graph below shows the distribution of \mathrm{cos} \theta over the Antarctic continent, where \theta is the angle between wind direction and local surface slope vector (both vector fields taken at the resolution of the ERA data =0.75^o). As expected, winds run overwhelmingly downslope, but with a large deflection from 180^o due to coriolis effect.

 


[1] The Inversion Wind Pattern over West Antarctica, Parish & Bromwich, 1986

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