CHARACTERISTICS OF GRAVITY WAVE SPECTRUM IN THE WINTER MESOPAUSE REGION

This paper utilizes horizontal velocity data with high resolution measured by 19 chaff rockets in the 80-105 km region during the DYANA campaign to study char-acteristics of vertical wavenumber spectrum of scalar horizontal velocity in winter. Results show that the mean vertical wavenumber spectrum in winter has a spec-tral slope of -3.02, which is quite consistent with the -3 spectral slope predicted by various saturation theories, therefore, this provides an observational evidence of a saturated gravity wave spectrum in winter. Comparison with various saturation theories shows that spectral amplitude of the winter spectrum is perfectly consistent with that spectral amplitude predicted by the linear saturation theory, but it is always lower than those spectral amplitudes predicated by the nonlinear saturation theories and measured by lidars. The winter spectrum, together with a saturated gravity wave spectrum in the polar summer obtained recently, shows collectively that our observational results support the linear saturation theory re-gardless of different seasons, different geographical locations, and different height regions. Dominant vertical wavelength of the winter spectrum is estimated to be 15km, which is slightly larger than the dominant vertical wavelength of 12.8km measured in summer.