{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/22205"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/22205","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Lidar studies of gravity waves in the mesopause region","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.","abstract_html":"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, <span class=\"etd-inline-math\">&omega;</span>-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.","abstract_has_math":true,"creators":["Senft, Daniel Charles"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Electrical Engineering","degree_department":null,"school":null,"contributors":["Gardner, Chester S."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T13:32:24Z","date_published":"2011-05-07T13:32:24Z","updated_at":"2026-07-22T22:25:19Z","subjects":["Geophysics","Engineering, Electronics and Electrical","Physics, Atmospheric Science"],"languages":["eng"],"rights":["Copyright 1991 Senft, Daniel Charles"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9210985","(UMI)AAI9210985"],"render_values":[{"text":"AAI9210985","href":null,"code":true},{"text":"(UMI)AAI9210985","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/22205","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Gardner, Chester S."]},{"key":"dc:creator","label":"Author","values":["Senft, Daniel Charles"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T13:32:24Z","10000-01-01","1991"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Geophysics","Engineering, Electronics and Electrical","Physics, Atmospheric Science"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1991 Senft, Daniel Charles"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9210985","(UMI)AAI9210985","http://hdl.handle.net/2142/22205"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["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).","Made available in DSpace on 2011-05-07T13:32:24Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9210985.pdf: 5540708 bytes, checksum: 167f3182db2ed496cfe1080e1739d29b (MD5) Previous issue date: 1991","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:56:02Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:26:10-05:00 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"]},{"key":"dc:title","label":"Title","values":["Lidar studies of gravity waves in the mesopause region"]}]}],"canonical_facts":{"dc:contributor":["Gardner, Chester S."],"dc:creator":["Senft, Daniel Charles"],"dc:date":["2011-05-07T13:32:24Z","10000-01-01","1991"],"dc:description":["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).","Made available in DSpace on 2011-05-07T13:32:24Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9210985.pdf: 5540708 bytes, checksum: 167f3182db2ed496cfe1080e1739d29b (MD5) Previous issue date: 1991","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:56:02Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:26:10-05:00 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"],"dc:identifier":["AAI9210985","(UMI)AAI9210985","http://hdl.handle.net/2142/22205"],"dc:language":["eng"],"dc:rights":["Copyright 1991 Senft, Daniel Charles"],"dc:subject":["Geophysics","Engineering, Electronics and Electrical","Physics, Atmospheric Science"],"dc:title":["Lidar studies of gravity waves in the mesopause region"],"dc:type":["text"],"thesis:degree_discipline":["Electrical Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:19Z"}