Lidar studies of gravity waves in the mesopause region

Senft, Daniel Charles

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https://hdl.handle.net/2142/22205 Copy

Description

Title

Lidar studies of gravity waves in the mesopause region

Author(s)

Senft, Daniel Charles

Issue Date

1991

Doctoral Committee Chair(s)

Gardner, Chester S.

Department of Study

Electrical and Computer Science

Discipline

Electrical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Geophysics
• Engineering, Electronics and Electrical
• Physics, Atmospheric Science

Language

eng

Abstract

• Nightly and seasonal variations in gravity wave activity in the mesopause region are examined by analyzing 60 nights of Na lidar observations obtained during a five-year period at Urbana, Illinois. The lidar data were used to calculate atmospheric density perturbations and their spectra. The atmospheric density variances, density vertical shear variances, vertical wind variances, $\omega$-spectra magnitudes, and m-spectra magnitudes all exhibit considerable nightly variability as well as strong annual and semi-annual variations with the largest values in summer. The annual mean value of the rms density perturbations is 5.6%, with a mid-summer value that is 2 to 3 times larger. The Richardson number for the wave field varies between 1/2 and 2 for most of the year, although Ri sometimes falls well below 1/4 during the summer.
• The $\omega$-spectra exhibit power-law shapes with slopes varying between $-$1.28 and $-$2.45, with an annual mean of $-$1.82. The m-spectra also exhibit power-law shapes with slopes varying between $-$2.20, and $-$3.55, with a mean of $-$2.90. The magnitudes of both the $\omega$-spectra and m-spectra vary by more than a factor of 10 throughout the year, with the largest values in summer. The variability of the m-spectra slopes and magnitudes is not consistent with linear instability theory and the concept of a universal vertical wave number spectrum. The characteristic periods (T$\sb\* = 2\pi/\omega\sb\*)$ vary between 3 and 50 h with an annual mean of 9.7 h. The characteristic vertical wavelengths ($\lambda\sb\*$ = 2$\pi$/m$\sb\*)$ vary between 8.9 and 27 km with an annual mean of 14.1 km. The rms bandwidths of the wave field have mean values of $\bar\omega\sb{\rm rms}$ = 2$\pi$/(44 min) and $\bar{\rm m}\sb{\rm rms}$ = 2$\pi$/(6.2 km).

Type of Resource

text

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http://hdl.handle.net/2142/22205

Copyright and License Information

Copyright 1991 Senft, Daniel Charles

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