Theoretical and Lidar Studies of the Density Response of the Mesospheric Sodium Layer to Gravity Wave Perturbations
Shelton, John Davis
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https://hdl.handle.net/2142/69228
Description
Title
Theoretical and Lidar Studies of the Density Response of the Mesospheric Sodium Layer to Gravity Wave Perturbations
Author(s)
Shelton, John Davis
Issue Date
1982
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Abstract
Laser radar observations of the mesospheric sodium layer often reveal wavelike density fluctuations moving through the layer. It is often assumed that these features are a layer density response to gravity waves. The density response of atmospheric layers to gravity waves is developed in two forms; an exact solution and a perturbation series solution. The degree of nonlinearity in the layer density response is clearly described by the series solution whereas the exact solution gives insight into the nature of the response. It is shown that density perturbations in an atmospheric layer can be substantially greater than the atmospheric density perturbations associated with the propagation of a gravity wave. Because of the density gradients present in atmospheric layers, interesting effects are observed such as a phase reversal in the linear layer response which occurs near the layer peak. Once the layer response is understood, the sodium layer can be used as a tracer of atmospheric wave motions.
In order to increase the resolution of lidar data, a two-dimensional digital signal processing technique has been developed. Both spatial and temporal filtering are utilized to enhance the resolution by decreasing shot noise by more than 10 dB. Many of the features associated with a layer density response to gravity waves are observed in high resolution density profiles of the mesospheric sodium layer. These include nonlinearities as well as the phase reversal in the linear layer response.
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