Large-Scale Atmospheric Circulation Characteristics as Evident from Ghost Balloon Data

Abstract

From GHOST balloon data obtained over the Southern Hemisphere at the 200-mb level, phase velocities of cyclone waves were found to vary between 6.3 and 9.2 degrees of longitude per day. Spectrum analysis of the relative velocities of balloon pairs, measured with respect to their common center of gravity, yielded a spectrum peak in the v component near frequencies of 1/52 hr, and a ??3? spectrum slope at higher frequencies. (The latter may be contaminated by a spline function smoothing technique.) Spectral densities in v were found to be slightly larger in summer than in winter, while densities in u were half as large in summer than in winter. Significantly stronger anisotropy of flow prevails at cyclone wavelengths in the Southern than the the Northern Hemisphere, with the v perturbations exceeding the zonal flow perturbations. GHOST balloon cospectra yielded similar results of momentum transport as did data from the Northern Hemisphere. Eulerian spectra of the v component over New Zealand agreed well with results from the Northern Hemisphere; spectral densities of the u component in the Southern Hemisphere,. however, were approximately half of those found in the Northern Hemisphere (Washington, D. C.); the v spectra showed a peak at 1/14 day. Spectrum slope5 of ??1? are indicated at higher frequencies. Eulerian cospectra permitted a preliminary estimate of meridional transports of zonal momentum. A crude estimate of the relation between Eulerian and Lagrangian spectra yielded considerably different results for the Southern than for the Northern Hemisphere as did estimates of the coefficients of eddy diffusivity Kx and Ky.