Multi-frequency Radar Studies of the High Latitude Mesosphere
The radar signature of Polar Mesosphere Summer Echoes (PMSE), which are associated with Noctilucent Clouds (NLC) (the highest clouds over the Earth), has been studied using Medium-Frequency (MF), High-Frequency (HF), and Very-High-Frequency (VHF) radars deployed over the central Alaskan region. The...
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ftcornelluniv:oai:ecommons.cornell.edu:1813/3847 2023-05-15T13:49:08+02:00 Multi-frequency Radar Studies of the High Latitude Mesosphere Ramos, Camilo 2006-11-17T18:01:02Z 72594749 bytes application/pdf https://hdl.handle.net/1813/3847 en_US eng bibid: 6476225 https://hdl.handle.net/1813/3847 Radiophysics Atmospheric Science Remote Sensing dissertation or thesis 2006 ftcornelluniv 2020-02-02T14:46:56Z The radar signature of Polar Mesosphere Summer Echoes (PMSE), which are associated with Noctilucent Clouds (NLC) (the highest clouds over the Earth), has been studied using Medium-Frequency (MF), High-Frequency (HF), and Very-High-Frequency (VHF) radars deployed over the central Alaskan region. The echo morphology at the different frequencies is described in case studies wherein PMSE events were observed concurrently using at least two radar systems. The identity of MF and HF radar echoes as PMSE is resolved for the first time by means of simultaneous measurements made with VHF radars, the reference sensors employed traditionally for PMSE studies. Radar reflectivity estimates, derived from in-situ rocket measurements, suggest that HF radars are optimal for the observation of PMSE edge-dominated type of scatter. MF radars, on the other hand, show comparable reflectivity values for edge and turbulent scattering components, as may be expected for wider antenna beam systems that are exposed to other echo sources. The VHF scattering calculations validate previous research on PMSE, suggesting an increase of the Schmidt number to maintain irregularities of scale sizes in the order of a few meters or less. A large Schmidt number is not needed at MF/HF frequencies since the wavelengths are larger than the Kolmogorov micro-scale and mesospheric layers can be sustained at low charging levels. Rocket measurements of mesospheric dust content and simultaneous analyzed MF radar backscattered power profiles show a similar type of structure. Dust particles are produced most likely by meteor trails reaching to the upper mesosphere region and may be related to some non-summer Mesospheric-radar Echoes (ME). On the basis of echo duration and signal strength, we suggest that HF radars are most favorable for PMSE monitoring. MF radars show highly organized PMSE layers quite often but are more susceptible to ionospheric absorption and higher altitude returns associated with geomagnetic activity. However, since a number of MF stations are located at polar or near polar latitudes, including Antarctica, it may be possible to use the PMSE signature studied here to investigate its long-term variability as well as its low latitude boundary. The latter could be an indicator of global change. Advisor: Professor Michael C. Kelley Account Number: E70 8353 Other/Unknown Material Antarc* Antarctica Cornell University: eCommons@Cornell |
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Open Polar |
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Cornell University: eCommons@Cornell |
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ftcornelluniv |
language |
English |
topic |
Radiophysics Atmospheric Science Remote Sensing |
spellingShingle |
Radiophysics Atmospheric Science Remote Sensing Ramos, Camilo Multi-frequency Radar Studies of the High Latitude Mesosphere |
topic_facet |
Radiophysics Atmospheric Science Remote Sensing |
description |
The radar signature of Polar Mesosphere Summer Echoes (PMSE), which are associated with Noctilucent Clouds (NLC) (the highest clouds over the Earth), has been studied using Medium-Frequency (MF), High-Frequency (HF), and Very-High-Frequency (VHF) radars deployed over the central Alaskan region. The echo morphology at the different frequencies is described in case studies wherein PMSE events were observed concurrently using at least two radar systems. The identity of MF and HF radar echoes as PMSE is resolved for the first time by means of simultaneous measurements made with VHF radars, the reference sensors employed traditionally for PMSE studies. Radar reflectivity estimates, derived from in-situ rocket measurements, suggest that HF radars are optimal for the observation of PMSE edge-dominated type of scatter. MF radars, on the other hand, show comparable reflectivity values for edge and turbulent scattering components, as may be expected for wider antenna beam systems that are exposed to other echo sources. The VHF scattering calculations validate previous research on PMSE, suggesting an increase of the Schmidt number to maintain irregularities of scale sizes in the order of a few meters or less. A large Schmidt number is not needed at MF/HF frequencies since the wavelengths are larger than the Kolmogorov micro-scale and mesospheric layers can be sustained at low charging levels. Rocket measurements of mesospheric dust content and simultaneous analyzed MF radar backscattered power profiles show a similar type of structure. Dust particles are produced most likely by meteor trails reaching to the upper mesosphere region and may be related to some non-summer Mesospheric-radar Echoes (ME). On the basis of echo duration and signal strength, we suggest that HF radars are most favorable for PMSE monitoring. MF radars show highly organized PMSE layers quite often but are more susceptible to ionospheric absorption and higher altitude returns associated with geomagnetic activity. However, since a number of MF stations are located at polar or near polar latitudes, including Antarctica, it may be possible to use the PMSE signature studied here to investigate its long-term variability as well as its low latitude boundary. The latter could be an indicator of global change. Advisor: Professor Michael C. Kelley Account Number: E70 8353 |
format |
Other/Unknown Material |
author |
Ramos, Camilo |
author_facet |
Ramos, Camilo |
author_sort |
Ramos, Camilo |
title |
Multi-frequency Radar Studies of the High Latitude Mesosphere |
title_short |
Multi-frequency Radar Studies of the High Latitude Mesosphere |
title_full |
Multi-frequency Radar Studies of the High Latitude Mesosphere |
title_fullStr |
Multi-frequency Radar Studies of the High Latitude Mesosphere |
title_full_unstemmed |
Multi-frequency Radar Studies of the High Latitude Mesosphere |
title_sort |
multi-frequency radar studies of the high latitude mesosphere |
publishDate |
2006 |
url |
https://hdl.handle.net/1813/3847 |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_relation |
bibid: 6476225 https://hdl.handle.net/1813/3847 |
_version_ |
1766250866933760000 |