The vertical structure of summertime local winds in the Wright Valley, Antarctica

Abstract

Intensive observations of summertime up- and down-valley winds in a “dry” valley utilising airsondes, pilot balloons and a monostatic acoustic sounder are described. Both circulations show a distinctive layered vertical wind and temperature structure. Westerly down-valley flow is typically neutral and is characterised by strong surface winds overlain by light variable winds extending to an inversion between 2000 and 4000m in depth. Above this inversion, gradient winds prevail. This structure is similar to that of downslope winds observed elsewhere. The thermally-induced up-valley easterly flow is shown to be extremely well-developed in terms of its strength, depth and persistence. The strong surface easterly may reach 800 m in depth and usually undercuts the warmer westerly. The boundary between the two regimes is marked by an inversion. During easterly flow a surface-based, super-adiabatic layer of 100–200 m in depth is evident and is associated with weak convective activity. An intriguing aspect of the wind regime is the interaction between the easterly and westerly circulations in the valley. These are separated at the surface by a frontal zone which migrates up and down the valley. Further observational and modelling studies are recommended.