The characteristics of the lower stratospheric gravity wavefield above Halley (75°S, 26°W), Antarctica, from radiosonde observations

Abstract

Daily radiosonde observations between 2003 and 2013 from Halley research station, Antarctica (75°S, 26°W), are used to determine climatologies of gravity wave properties in the lower stratosphere (between 15 km and 22 km altitude). Individual waves are extracted from the radiosonde profile using wavelet analysis and separated into upward and downward propagating waves. An increase in the percentage of downward propagating waves (~30% of the waves) is seen during the winter months. For the upward and downward propagating waves, their horizontal and vertical wavelength, intrinsic frequency, energy density, pseudomomentum flux, and direction of propagation are determined. The upward propagating wavefield is found to be dominated by waves with short vertical wavelength (~1 km) and low intrinsic frequency (ω ~ f). The downward propagating wavefield is composed of a wider distribution of vertical wavelength waves and has a larger proportion of higher-frequency waves present. The upward propagating waves show an increase in total energy density in autumn and spring; the larger increase occurs during spring (up to 1.7 J kg−1 in September). The downward propagating waves increase in total energy density occurs during wintertime (up to 0.7 J kg−1 in June). During winter the contributions of the upward and downward propagating waves to the total energy density and pseudomomentum flux are almost equal. This paper details the first study of individual gravity wave properties combined into upward and downward propagating wave climatologies in the lower stratosphere above Halley.