OBSERVATIONS OF HORIZONTAL AND VERTICAL WAVE-NUMBER SPECTRA OF GRAVITY-WAVE MOTIONS IN THE STRATOSPHERE AND MESOSPHERE OVER THE MID-PACIFIC

We present vertical and horizontal wave number spectra of density pert urbations in the upper stratosphere (25-40 km) and the upper mesospher e (similar to 80-105 km) inferred from similar to 45 hours of airborne Na/Rayleigh lidar observations in the vicinity of Hawaii. The mean de nsity variance is (0.92%)(2) for the upper stratosphere and (6.1%)(2) and for the upper mesosphere. The mean vertical shear variance and Ric hardson's number for the upper mesosphere are (6.l%/km)(2) and 0.69, r espectively. The observed vertical wave number m and horizontal wave n umber k spectra exhibit power law dependencies. The mean slopes of the vertical wave number spectra are -2.5 for the upper stratosphere and -3.1 for the upper mesosphere. The mean slope of the horizontal wave n umber spectra is -1.9 for the upper mesosphere. The mean characteristi c vertical and horizontal wavelengths inferred from the spectra are 13 .4 and 5810 km, respectively. In all cases the magnitudes of the upper stratosphere m spectra are more than an order of magnitude smaller th an those of the upper mesosphere at all observable scales. In the stra tosphere the m spectra exhibit significant energy at low wave numbers that are less than the values expected for the characteristic wave num bers. This suggests the presence of gravity wave sources capable of ge nerating significant energy at long vertical scales. The source is bel ieved to be geostrophic adjustment of the jet stream. A large-amplitud e, highly coherent, quasi-monochromatic, short horizontal scale (lambd a(h) similar to 16 km) oscillation in the Na layer was observed on the March 22 flight. The oscillation resembled short horizontal scale str uctures often observed in OH airglow images and was found to be consis tent with a gravity wave interpretation.