A numerical study of the diurnal variation of the Adelie Land katabatic wind regime

Abstract

Katabatic winds occur with great frequency over the Adelie Land sector of Antarctica. Data collected by automatic weather stations (AWSs) along a string of stations from the coast of Adelie Land to the high interior plateau show a marked diurnal cycle of the wind and temperature regimes of the lower atmosphere during the short austral summer period. Numerical simulations of the katabatic wind regime have been conducted for a variety of solar forcing and synoptic conditions assuming a clear sky environment. Results suggest that the katabatic wind is a robust feature of the Antarctic boundary layer. Significant disruption of the low‐level drainage features occurs only during the midsummer months owing to the solar heating of the ice slopes and from synoptic activity along the Adelie Land coastline. During midsummer, modeled ground temperatures undergo a diurnal cycle with an amplitude of 15°C near the coast, in good agreement with the AWS observations. The katabatic wind decreases considerably during the middle of the day; wind speeds at coastal sites become reduced by more than one half of the early morning values. The numerical simulations depict a rapid summer to winter transition of katabatic wind conditions over the 1‐month period from mid‐February to mid‐March. The surface energy budget becomes negative for the entire 24‐hour period after mid‐February, corresponding to the rapid onset of the wintertime katabatic wind regime.