Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry
| Main Author: | |
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| Publication Date: | 2013 |
| Language: | eng |
| Source: | Repositórios Científicos de Acesso Aberto de Portugal (RCAAP) |
| Download full: | http://hdl.handle.net/10451/10525 |
Summary: | Tese de doutoramento (co-tutela), Astronomia e Astrofísica, Observatoire de Paris, Universidade de Lisboa, 2013 |
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Characterization of the dynamics of the atmosphere of Venus with doppler velocimetryTeses de doutoramento (co-tutela) - 2013Tese de doutoramento (co-tutela), Astronomia e Astrofísica, Observatoire de Paris, Universidade de Lisboa, 2013Currently the study of the Venus’ atmosphere grows as a theme of major interest among the astrophysics scientific community. The most significant aspect of the general circulation of the atmosphere of Venus is its retrograde super-rotation. A complete characterization of this dynamical phenomenon is crucial for understanding its driving mechanisms. This work participates in the international effort to characterize the atmospheric dynamics of this planet in coordination with orbiter missions, in particular with Venus Express. The objectives of this study are to investigate the nature of the processes governing the super-rotation of the atmosphere of Venus using ground-based observations, thereby complementing measurements by orbiter instruments.This thesis analyzes observations of Venus made with two different instruments and Doppler velocimetry techniques.The first part of the thesis presents ground-based Doppler velocimetry measurements of the zonal winds based on observations carried out with the Ultraviolet and Visual Echelle Spectrograph at ESO’s Very Large Telescope. Using Doppler-shifted Fraunhofer lines from the solar spectrum, this high resolution spectrograph (R 100,000) allows to measure the velocity of Venus’ upper cloud layer with a precision of about 5 ms1. Under the assumption of predominantly zonal flow, this method allows the simultaneous direct measurement of the zonal velocity across a range of latitudes and local times in the day side. The technique, based on long slit spectroscopy combined with the observations’ high spatial resolution, has provided the first ground-based characterization of the latitudinal profile of zonal wind in the atmosphere of Venus, the first zonal wind field map in the visible, as well as new constraints on wind variations with local time. Mean zonal wind amplitudes were measured between 106 21 and 127 14 ms1 at latitudes between 18 N and 34 S, with the zonal wind being approximately uniform in 2:6 -wide latitude bands (0:3” at disk center).The zonal wind profile retrieved is consistent with previous spacecraft measurements based on cloud tracking, but with non-negligible variability in local time (longitude) and in latitude. Near 50 the presence of moderate jets is apparent in both hemispheres, with the southern jet being stronger by 10 ms1. Small scale wind variations with local time are also present at low and mid-latitudes (Machado et al., 2012).The second part of the thesis presents results of Venus’ mesospheric winds at cloud top level, based on ground-based Doppler velocimetry of cloud-top winds and inter comparison of cloud tracking measurements from the Venus Express spacecraft.Doppler wind velocimetry obtained with the 3.60 m Canada-France-Hawaii telescope (CFHT) and the visible spectrograph ESPaDOnS in February 2011 consisted of high-resolution spectra of Fraunhofer lines in the visible range to measure the wind velocity using the Doppler shift of solar radiation scattered by cloud top particles in the observer’s direction (Widemann et al., 2007, 2008; Machado et al., 2013). The complete optical spectrum was collected at a phase angle = (68:7 0:3) , at a resolution of about 80,000. The obtained ground-based measurements on Venus are compared with simultaneous observations using the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument from the VEx orbiter. CFHT observations included various points of the dayside hemisphere observed at a phase angle of 67 from CFHT, between +10 N and 60 S, by steps of 10 , and from sub-Earth longitude [ E ] = 0 to -50 corresponding to 7:30a - 10:50a, while VIRTIS-M UV (0.38 m) cloud tracking measurements extended on the dayside south hemisphere between 30 and 50 S and 9:05a - 10:50a at simultaneous spacecraft orbit VV1786. Doppler wind retrievals using either 1- or 2-wind circulation regimes are in good agreement with measurements based on cloud tracking from Venus Express.Were observed zonal wind field variations in the latitudinal and temporal scales within stable mean background velocities of vz = 117.35 18.0 ms1 on Feb. 19, and vz = 117.5 14.5 ms1 on Feb. 21, respectively. It is presented the first unambiguous detection from the ground of a poleward meridional wind flow on the morning dayside hemisphere, of 18.8 11.5 ms1 on Feb. 19, and 19.0 8.3 ms1 on Feb. 21. Wind temporal, local variation at the hour-scale of 18.5 ms1 were detected near morning terminator at low latitude. To provide the best description of the wind field observed, the retrieved results were compared to a series of wind circulation models and their characterization at cloud top level.The data analysis technique allowed an unambiguous characterization of the zonal wind latitudinal profile and its temporal variability, as well as an investigation of large-scale planetary waves signature and their role in the maintenance of the zonal super-rotation, and suggest that detection and investigation of large-scale planetary waves can be carried out with this technique.These studies complement the independent observations of the european space mission Venus Express, in particular as regards the study of atmospheric super-rotation, meridional flow and its variability.Fundação para a Ciência e a Tecnologia (FCT, PhD grant SFRH/BD/66473/2009)Luz, David Manuel Guerreiro Carmo da, 1972-Widemann, ThomasRepositório da Universidade de LisboaMachado, Pedro2014-02-12T14:22:48Z20132013-01-01T00:00:00Zdoctoral thesisinfo:eu-repo/semantics/publishedVersionapplication/pdfhttp://hdl.handle.net/10451/10525TID:101324731enginfo:eu-repo/semantics/openAccessreponame:Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)instname:FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologiainstacron:RCAAP2025-03-17T13:06:02Zoai:repositorio.ulisboa.pt:10451/10525Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireinfo@rcaap.ptopendoar:https://opendoar.ac.uk/repository/71602025-05-29T02:34:58.155068Repositórios Científicos de Acesso Aberto de Portugal (RCAAP) - FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologiafalse |
| dc.title.none.fl_str_mv |
Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry |
| title |
Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry |
| spellingShingle |
Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry Machado, Pedro Teses de doutoramento (co-tutela) - 2013 |
| title_short |
Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry |
| title_full |
Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry |
| title_fullStr |
Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry |
| title_full_unstemmed |
Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry |
| title_sort |
Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry |
| author |
Machado, Pedro |
| author_facet |
Machado, Pedro |
| author_role |
author |
| dc.contributor.none.fl_str_mv |
Luz, David Manuel Guerreiro Carmo da, 1972- Widemann, Thomas Repositório da Universidade de Lisboa |
| dc.contributor.author.fl_str_mv |
Machado, Pedro |
| dc.subject.por.fl_str_mv |
Teses de doutoramento (co-tutela) - 2013 |
| topic |
Teses de doutoramento (co-tutela) - 2013 |
| description |
Tese de doutoramento (co-tutela), Astronomia e Astrofísica, Observatoire de Paris, Universidade de Lisboa, 2013 |
| publishDate |
2013 |
| dc.date.none.fl_str_mv |
2013 2013-01-01T00:00:00Z 2014-02-12T14:22:48Z |
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doctoral thesis |
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info:eu-repo/semantics/publishedVersion |
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publishedVersion |
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http://hdl.handle.net/10451/10525 TID:101324731 |
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http://hdl.handle.net/10451/10525 |
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TID:101324731 |
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eng |
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eng |
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info:eu-repo/semantics/openAccess |
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openAccess |
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