Katabatic Winds In Adelie Land, Antarctica (Snow, Automatic Weather Stations, Pressure Gradient, Coreless Winter)

Abstract

Data from Automatic Weather Stations (AWS) on Adelie Land, Antarctica, were analysed. The findings are: (1) The high directional constancy of surface winds, which has been explained by the inversion strength and topography of the slope, was found at the slope stations even in summer when the inversion is weak or destroyed. An analysis of data and model simulations of diurnal variations of katabatic winds in summer show that synoptic geostrophic winds and eddy viscosity also effect the constancy of the wind direction in summer. (2) Wind directional constancies at the slope stations in winter, when the inversion is expected to be stronger than that in summer, are sometimes lower than the mean annual constancies. These low constancies are associated with warm air advection from maritime air brought into Adelie Land when the continental anticyclonic ridge lies to the east of Adelie Land. (3) There is a superadiabatic surface temperature change between the high plateau and intermediate plateau stations. The comparison of the terms in the total pressure gradient force showed that the superadiabatic surface temperature change along the slope could be of importance for surface flow when the buoyancy component is balanced or nearly balanced by an increase in depth of the katabatic wind layer. (4) The entrainment of blowing snow particles increases the density of the katabatic flow layer by two mechanisms: first, by the addition of snow particles to the air column; and second, by the sublimation of the snow particles. This increase in density in the katabatic flow layer leads to increased wind speed. This accelerative effect occurs primarily at wind speeds exceeding 12 m/s, since at those high wind speeds there is usually a large amount of blowing snow.