Observations of an internal gravity wave in the lower troposphere at Halley, Antarctica

Observations of internal gravity waves in the stably stratified atmospheric boundary layer at Halley, Antarctica, are presented. These were made on Feb. 1, 1986, and take the form of temperature measurements from a 30-m mast and a sodar record. The temperature record shows a clearly defined, dominant wave period of similar to 11 min. A high-resolution radiosonde ascent made during the period of wave activity exhibits thin layers of low Richardson number, and it is suggested that these are regions of dynamic instability where the waves are generated. A linear stability analysis of the radiosonde data supports this idea. It is argued from simple theoretical ideas and with a numerical model that only waves with a wavelength greater than a certain critical value are likely to be observed at the surface. The observations are shown to be consistent with this hypothesis.