Rayleigh Lidar Observations of Gravity Wave Activity in the Upper Stratosphere at Urbana, Illinois.
ILLINOIS UNIV AT URBANA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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During the 13 night of Rayleigh lidar measurements thirty-six quasi- monochromatic gravity waves were observed in the 35 to 50 km altitude region of the stratosphere. The characteristics of the waves are compared with other lidar and radar measurements of gravity waves and with theoretical models of wave saturation and dissipation phenomena. The measured vertical wavelengths lambda from 2 to 11.5 km and the measured vertical phase velocities c sub z ranged from 10 85 cms. The vertical wavelengths and vertical phase velocities were used to infer observed wave periods T sub ob which ranged from 100 to 1000 min and horizontal wavelengths lambda sub x which ranged from 70 to 2000 km. However, there may be errors in the inferred values of the horizontal wavelengths because they were calculated by assuming that the observed period equals the intrinsic period. Dominant wave activity was found at vertical wavelengths between 2-4 km and 7-10 km. No significant seasonal variations were evident in the observed parameters. Vertical and horizontal wavelengths showed a clear tendency to increase with T sub ob, which is consistent with recent sodium lidar studies of quasi-monochromatic waves near the mesopause. An average amplitude growth length of 20.9 km for rms wind perturbations was estimated from the data. Kinetic energy density associated with the waves decreased with height, suggesting that waves in this altitude region were subject to dissipation or saturation effects. jhd