A climatological study of internal gravity waves in the atmospheric boundary layer overlying the Brunt Ice Shelf, Antarctica

Internal gravity waves are frequently observed in stably stratified regions of the atmospheric boundary layer. In order to determine the statistical influence of such waves on the dynamics of the boundary layer it is necessary to compile information concerning properties of the waves such as frequency of occurrence, propagation, and spectral characteristics. Gravity wave climatologies have been compiled from relatively few locations. In this paper a climatological study of gravity waves, in the period range 1-20 min, propagating in the stably stratified atmospheric boundary layer overlying an Antarctic ice shelf is presented. An extensive set of boundary layer measurements were compiled throughout 1991. Surface pressure fluctuations were recorded from a spatial array of six sensitive microbarographs. Wind and temperature records from an instrumented mast were also available. A beam-steering technique has been used to determine wave parameters from the surface pressure data. The microbarographs detected the presence of internal gravity waves throughout the observational campaign. Root-mean-square pressure values were typically in the region 16-40 mu b, but a significant number of isolated events with amplitudes of up to 180 mu b were also found. Wave properties have been studied in conjunction with the mean wind and temperature profiles in the boundary layer. It was found that most of the wave activity did not originate locally, but from shear layers aloft, or, more commonly, from the katabatic flow regime where the ice shelf joins the Antarctic continent.