2026-09-22T10:54:15Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/21059 2023-07-10 col_2142_5131 col_2142_8888 com_2142_5130 com_2142_8887 com_2142_234

Gardner, Chester S. Bills, Richard Earl 2011-05-07T12:57:09Z 2011-05-07T12:57:09Z 10000-01-01 1991 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. Made available in DSpace on 2011-05-07T12:57:09Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9210745.pdf: 5863466 bytes, checksum: 362cfecf28b2d41cfad7a47afa52d4b0 (MD5) Previous issue date: 1991 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:48:12Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:21:48-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9210745 (UMI)AAI9210745 http://hdl.handle.net/2142/21059 eng Copyright 1991 Bills, Richard Earl Engineering, Electronics and Electrical Physics, Atmospheric Science Physics, Optics Iron and sodium Doppler/temperature lidar studies of the upper mesosphere text Electrical and Computer Engineering Electrical Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.