A Climatological Study of Internal Gravity Waves in the Atmospheric Boundary Layer Overlying the Brunt Ice Shelf, Antarctica

Abstract

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. Rootmean-square pressure values were typically in the region 16-40 b, but a significant number of isolated events with amplitudes of up to 180 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. * Current affiliation:

Statistics of Turbulence in the Stable Boundary Layer Affected by Gravity Waves

“…Wave effects are usually detected on temporal and spatial records of in situ and remote sensors as fluctuations or undulations of pressure, temperature, reflectivity, and refractive index, with periods in the range from about a minute to about an hour, and wavelengths from 100 m to several km (e.g. Rees et al 2000).…”

Influence of stability on the flux-profile relationships for wind speed, <i>Φ</i><sub>m</sub>, and temperature, <i>Φ</i><sub>h</sub>, for the stable atmospheric boundary layer

“…At the higher levels, z=13.5 m and 32 m, there is little evidence of the similarity function following Businger's or Webb's functions. In fact, if a detailed analysis of the structure of the ABL is performed when high φ h values are present with low ζ , a complex structure of the lower atmosphere can be seen which is influenced by the presence of internal waves (Nai-Ping et al, 1983;Rees et al, 2000). These low values of ζ (for the S-period) are not truly neutral points and should not be used to do a fit in this range.…”

Characteristics of Gravity Waves over an Antarctic Ice Sheet during an Austral Summer

“…Typical periods of GWs range from a few minutes to approximately one hour, whereas the wavelengths vary from about hundreds of meters to several kilometres [10]. GWs may be generated by several mechanisms, including topographic forcing, dynamical instabilities (i.e., shear instability, microfronts or mesoscale fronts) and wave-wave interactions [11][12][13][14][15].…”