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Wind speed vertical distribution at Mt Graham
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
2010 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 407, no 4, 2230-2240 p.Article in journal (Refereed) Published
Abstract [en]

The characterization of the vertical distribution of wind speed, V (h), is fundamental for anastronomical site for many different reasons: (i) the wind speed shear contributes to triggeroptical turbulence in the whole troposphere; (ii) a few of the astroclimatic parameters, suchas the wavefront coherence time (τ0), depend directly on V (h); (iii) the equivalent velocityV0, controlling the frequency at which the adaptive optics systems have to run in order towork properly, depends on the vertical distribution of the wind speed and optical turbulence.Also, too strong a wind speed near the ground can introduce vibrations in the telescopestructures. The wind speed at a precise pressure (200 hPa) has frequently been used to retrieveindications concerning τ0 and the frequency limits imposed on all instrumentation based onadaptive optics systems. However, more recently, it has been proved that V200 (the wind speedat 200 hPa) alone is not sufficient to provide exhaustive elements concerning this topic, andthus the vertical distribution of the wind speed is necessary. In this paper, we report on acomplete characterization of the vertical distribution of wind speed strength, which has beencarried out above Mt Graham (Arizona, USA), the site of the Large Binocular Telescope.We provide a climatological study extended over 10 yr using the operational analyses fromthe European Centre for Medium-Range Weather Forecasts (ECMWF). We prove that this isrepresentative of the vertical distribution of the wind speed at Mt Graham, with the exceptionof the boundary layer. We also prove that a mesoscale model can provide reliable nightlyestimates of V (h) above this astronomical site from the ground up to the top of the atmosphere(∼20 km).

Place, publisher, year, edition, pages
2010. Vol. 407, no 4, 2230-2240 p.
Keyword [en]
turbulence, atmospheric effects, methods: data analysis, site testing
National Category
Earth and Related Environmental Sciences Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-132795DOI: 10.1111/j.1365-2966.2010.17102.xISI: 000281948100015OAI: oai:DiVA.org:uu-132795DiVA: diva2:359205
Available from: 2010-10-27 Created: 2010-10-27 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Optical Turbulence Characterization for Ground-Based Astronomy
Open this publication in new window or tab >>Optical Turbulence Characterization for Ground-Based Astronomy
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The optical turbulence, which creates perturbations of the wavefronts coming from the stars, is caused by small-scale fluctuations in the index of refraction of the atmosphere and is a problem for astronomers because it limits the maximum resolution of the ground-based telescopes. One way of identifying the best sites to build astronomical observatories, where the influence of the optical turbulence is as small as possible, is to use the standard meteorological parameters to get a first idea of the potential of a site. In the first part of this thesis the three sites on the Internal Antarctic Plateau that are the most interesting for astronomers (Dome A, Dome C and the South Pole) are investigated using the operational analyses of the ECMWF and a ranking of these three sites is presented.

The second part of this thesis focuses on the ability of the mesoscale model Meso-NH to simulate the optical turbulence as well as the wind speed at Mt Graham (AZ, USA). A rich sample of measurements of the vertical distribution of the optical turbulence, the largest sample used in this type of study so far, is used to calibrate the Meso-NH model and to quantify its ability to simulate the optical turbulence. The measurements are distributed over different periods of the year thus making it possible to evaluate the performance of the model in different seasons. Both the vertical distribution of the optical turbulence and the astroclimatic parameters (seeing, wavefront coherence time and isoplanatic angle) are investigated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 68 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 778
Keyword
site testing, atmospheric effects, turbulence, optical turbulence, applied meteorology, mesoscale models
National Category
Meteorology and Atmospheric Sciences Astronomy, Astrophysics and Cosmology
Research subject
Meteorology
Identifiers
urn:nbn:se:uu:diva-132798 (URN)978-91-554-7926-8 (ISBN)
Public defence
2010-12-09, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
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Note
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 708Available from: 2010-11-17 Created: 2010-10-27 Last updated: 2011-03-21Bibliographically approved

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Hagelin, Susanna

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