Anisotropy of the horizontal velocity fluctuation field in the large wavenumber region

Abstract

This paper utilizes meridional and zonal velocity data measured by chaff rockets at a high resolution of 25 m in the 67—96 km region during the MAC/SINE campaign to study the characteristics of the spectra of the meridional and zonal velocity fluctuations. Results suggest that the mean vertical wavenumber spectra have a forked point near vertical wavenumber k = 0.001 m −1 . In the vertical wavenumber region smaller than the forked point, the spectra of the meridional and zonal velocities have approximately the same spectral slope, amplitude, and characteristic vertical wavelength, and agree well with the linear saturated spectral model. In the vertical wavenumber region larger than the forked point, however, the meridional and zonal spectra are inconsistent not only in both slope and amplitude, but also in spectral structure. The differences between the observed meridional and zonal spectra provide observational evidence of azimuthal anisotropy of the velocity fluctuation field in the large vertical wavenumber region in mean sense.