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Title:Iron and sodium Doppler/temperature lidar studies of the upper mesosphere
Author(s):Bills, Richard Earl
Doctoral Committee Chair(s):Gardner, Chester S.
Department / Program:Electrical and Computer Engineering
Discipline:Electrical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Electronics and Electrical
Physics, Atmospheric Science
Physics, Optics
Abstract:Lidar measurements of mesospheric Fe were conducted at Urbana, Illinois, during four nights in late October 1989. The average Fe abundances, layer centroid heights and rms widths varied between 1.0-2.0 $\times$ 10$\sp{10}$ cm$\sp{-2}$, 89.0-90.5 km and 3.2-4.1 km, respectively. The peak densities of the layer near 90 km varied between 15-25 $\times$ 10$\sp3$ cm$\sp{-3}$. On three nights the formation and dissipation of three large sporadic Fe (Fe$\sb{\rm s}$) layers were observed.
A new two-frequency lidar technique for measuring mesospheric Na temperature profiles is described. This system uses a stabilized cw single-mode dye laser oscillator (rms frequency jitter $<$1 MHz) followed by a pulsed dye power amplifier (140 MHz FWHM linewidth) which is pumped by an injection-seeded Nd:YAG laser. The laser oscillator is tuned to the two operating frequencies by observing the Doppler-free structure of the Na D$\sb2$ fluorescence spectrum in a vapor cell. The lidar technique and the initial observations are described. Absolute temperature accuracies at the Na layer peak of better than $\pm$3 K with a vertical resolution of 1 km and an integration period of approximately 5 min were achieved in this initial experiment.
Fourteen nights of Na temperature lidar data spanning 6 months were collected at Urbana, Illinois, using the two-frequency technique. The temperature structure over the 80-100 km region was highly variable due to the influence of gravity waves, tides, and sporadic layers (Na$\sb{\rm s}).$ Extreme temperatures of 140 K and 255 K were measured. A mesopause cooling rate of 9 K/month was exhibited from winter to summer at the mesopause height localized between 85 and 90 km. The temperature dependence of the Na column abundance is analyzed, and a 9 $\times$ 10$\sp7$ atoms/cm$\sp2/$K Na abundance rate of change was observed from winter to summer. The rms perturbations, wave dynamics, and Brunt-Vaisala periods are also investigated.
The first observations of vertically resolved Na density, temperature, and wind profiles in the mesopause region were made using a new four-frequency Doppler/temperature lidar. The initial zonal wind and temperature observations were obtained with a profile resolution of 30 min and 1.5 km and rms accuracies of 12 m/s and 2 K. These measurements were conducted simultaneously with the medium frequency (MF) radar at the Urbana Atmospheric Observatory (40$\sp\circ$N, 88$\sp\circ$W) during the night of 14-15 March, 1991. Although both the lidar and radar wind measurements exhibited the same general trends, the velocity estimates differed by as much as 40 m/s at some times during the night.
Issue Date:1991
Rights Information:Copyright 1991 Bills, Richard Earl
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9210745
OCLC Identifier:(UMI)AAI9210745

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