Date of Award

Winter 2004

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

First Advisor

James Ryan

Abstract

GroundWinds lidar system is a high-spectral-resolution lidar system that can directly measure the Rayleigh-Brillouin scattering (RBS) spectra, from which the wind, temperature, and turbulence in the troposphere can be measured. Its transmitter is a double-frequency Nd-YAG laser at 532nm. Most of the data used in this research were taken on 31 July 2002.

A widely used mathematic model---the S6 model---is fitted to the measured RBS spectra. The discrepancies between the measured temperature from the RayleighBrillouin spectra and from the radiosonde, combined with the discrepancies between the model and the measured RBS spectra, indicate that there is room for the S6 model to be improved. On the other hand, they also reveal that air turbulence information, which---along with the variance analysis---can be used in the turbulence measurements. The change in Rayleigh-Brillouin scattering spectra in fluids under external forces was theoretically investigated and can be used for acoustic wave detections, low-frequency plasma studies and other applications.

In addition, Rayleigh backscatter coefficients in air, for the first time, were measured using the molecular photometric returns. The measured molecular backscatter coefficients are approximately twice as large as their theoretical counterparts. This could be related to the collective effects of air molecules, i.e., the scattering structure factor.

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