Estimation of gravity wave parameters and their relations to the characteristics of the lower atmospheric layer

Several series of atmospheric pressure measurements performed at three site s with simultaneous recordings of other meteorological parameters on the Ob ninsk 300-m high meteorological tower were discussed. The parameters of int ernal gravity waves (IGWs) were derived from the phase shifts of the cross spectra of pressure fluctuations at the measurement sites (each triangle si de was about 300 m), To reveal their relations to the characteristics of th e lower parr of the boundary layer, data on temperature and wind-velocity p ulsations within the 300-m layer were used. Two cases of IGW occurrence at night with periods of 200-300 s were investigated. One of them was clearly related to a surface-inversion atmospheric waveguide. The cross spectra of the meteorological parameters had clearly defined peaks at IGW frequencies, but the phase shifts were close to pi/2. The second nighttime case corresp onded to an IGW that apparently propagated above the surface waveguide, bec ause pulsations of meteorological parameters were not observed at IGW frequ encies. A nearly monochromatic IGW was considered to be a narrow-band proce ss to determine the temporal evolution of its amplitude. Two other cases un der consideration corresponded to unstable and indifferent stratification. In the first of them, convective structures resulted in pressure spectra si milar to those occurring in the presence of IGWs, with peaks at periods of 200-300 s. In the second case, only small-scale turbulence was observed.