Chapter 6 - Mesoscale systems and processes

Summary

Local wind systems

The effect of local topography on katabatic flow

In Section 4.3, we saw how the near-surface wind field over much of Antarctica could be explained using simple diagnostic models of the katabatic wind. Such models provide realistic simulations of the mean wind at stations where the local topographic slope is reasonably uniform and not too great. However, the neglect of the non-linear inertial terms in these simplified models is not justified in regions where the topographic slope varies significantly. In such regions the advection of momentum and heat by the katabatic wind must be taken into account in order to model the local wind system correctly.

A number of coastal regions of Antarctica are subject to exceptionally strong katabatic winds. These include the coast of Adélie Land between Port Martin and Cape Denison. The annual mean wind speed at Cape Denison, measured by Mawson's Australasian Antarctic Expedition during 1912–14, was 19.3 m s⁻¹, with monthly mean speeds never dropping below 12.9 m s⁻¹ (Parish, 1981). At nearby Port Martin, occupied by a French expedition during 1950–52, mean wind speeds were only slightly lower, with an annual mean of 16.9 m s⁻¹. However, the zone affected by these intense katabatic winds appears to be limited and does not extend as far as Dumont d'Urville, some 65 km west of Port Martin. Limited information from inland traverses suggests that the region of extreme winds extends at least 250 km inland from Cape Denison (Parish and Wendler, 1991).