Wavelet analysis of stratosphere gravity wave packets over Macquarie Island 1. Wave parameters

Abstract

We describe a technique to detect gravity wave packets in high-resolution radiosonde soundings of horizontal wind and temperature. The vertical profiles of meridional and zonal wind speeds are transformed using the Morlet wavelet, and regions of high wind variance in height-wavenumber space are identified as gravity wave packets. Application of the Stokes parameter analysis to horizontal wind and temperature profiles of the reconstructed wave packets yields the wave parameters. The technique was applied to twice-daily radiosonde launches at Macquarie Island (55°S, 159°E) between 1993 and 1995. A strong seasonal cycle in the total wave variance was found, with a maximum in winter. The amount of wave energy propagating downward from the upper stratosphere also maximized in winter. Waves propagated predominately toward the southwest in winter, but in summer propagation directions were approximately isotropic. The intrinsic frequencies were close to the inertial frequency, and the waves had inferred horizontal wavelengths of several hundred kilometers.