Sampling the ground layer of the atmosphere at Dome C using fast sonic-anemometers

Travouillon, Tony; Aristidi, Éric; Fossat, E.; Lawrence, Jon; Mékarnia, D.; Moore, Anna; Skidmore, A. W.; Storey, J. W. V.

doi:10.1117/12.788503

Cited by 9 publications

(6 citation statements)

References 4 publications

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“…The trend of the two curves is similar, but NOAA velocities are slightly larger than SSS velocities. The mean wind speed of the slowest surface layer detected by the SSS is around 6 m s À1 at 8 m above ice level, also observed by Travouillon et al (2008). Lascaux et al (2009, with Méso-NH weather simulations) and Hagelin et al (2008, with radiosounding observations) found a wind speed above the ice level of about 4 m s À1 (at ground level) and 8 m s À1 (at 20 m above ground level, in the middle of the winter), respectively, which are very close to our SSS measurements.…”

Section: Vertical Profiles and Wind-speed Evolutionsupporting

confidence: 71%

Dome C Site Characterization in 2006 with Single-Star SCIDAR

Giordano¹,

Vernin²,

Chadid³

et al. 2012

Publications of the Astronomical Society of the Pacific

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We present observations made in 2006 with the single-star SCIDAR (SSS) at Dome C in Antarctica, allowing us to determine optical turbulence C 2 N ðhÞ and velocity VðhÞ profiles from ice levels up to about 25 km above sea level (a.s.l.). SSS is a 16 inch telescope placed on an equatorial mount that continuously tracks the Canopus star. About 90,000 individual profiles are analyzed from March to September, where surface-layer contribution to seeing can be separated from the rest of the atmosphere. Medians of high angular resolution parameters relevant to astronomy are statistically studied, such as seeing (1.0′′), isoplanatic angle (6.9′′), and wavefront coherence time (3.4 ms). For a telescope placed above the turbulent surface layer, superb conditions are encountered (medians of seeing better than 0.3′′, isoplanatic angle better than 6.9′′, and coherence time larger than 10 ms). Astronomical conditions are twice as good at the beginning of the night, with ε 0 ≈ 0:5 00 , θ 0 ≈ 11:5 00 , and τ 0 ≈ 15 ms. SSS wind-velocity profiles are consistent with National Oceanic and Atmospheric Administration analysis up to 17 km (a.s.l.), within a AE2 m s À1 error bar. Coherence étendue (which is a combination of ε 0 , θ 0 , and τ 0 ), well adapted to adaptive optics performances, is likely 4 times better at Dome C than at the already-known observatories such as Mauna Kea or ORM.

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Section: Vertical Profiles and Wind-speed Evolutionsupporting

confidence: 71%

Dome C Site Characterization in 2006 with Single-Star SCIDAR

Giordano¹,

Vernin²,

Chadid³

et al. 2012

Publications of the Astronomical Society of the Pacific

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“…During the polar summers 2006-2007 and 2007-2008 a set of 6 sonic anemometers was installed on the 45 m mast to perform in situ monitoring of the temperature, wind speed and C 2 n inside the BL (Travouillon et al 2008). A part of the data corresponding to the winter 2007 are under analysing, but in 2007 the mast was only 33 m high and there were 3 sonic anemometers.…”

Section: Resultsmentioning

confidence: 99%

Dome C site testing: surface layer, free atmosphere seeing, and isoplanatic angle statistics

Aristidi¹,

Fossat²,

Agabi³

et al. 2009

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This paper analyses 3 1 2 years of site testing data obtained at Dome C, Antarctica, based on measurements obtained with three DIMMs located at three different elevations. Basic statistics of the seeing and the isoplanatic angle are given, as well as the characteristic time of temporal fluctuations of these two parameters, which we found to around 30 min at 8 m. The 3 DIMMs are exploited as a profiler of the surface layer, and provide a robust estimation of its statistical properties. It appears to have a very sharp upper limit (less than 1 m). The fraction of time spent by each telescope above the top of the surface layer permits us to deduce a median height of between 23 m and 27 m. The comparison of the different data sets led us to infer the statistical properties of the free atmosphere seeing, with a median value of 0.36 arcsec. The C 2 n profile inside the surface layer is also deduced from the seeing data obtained during the fraction of time spent by the 3 telescopes inside this turbulence. Statistically, the surface layer, except during the 3-month summer season, contributes to 95 percent of the total turbulence from the surface level, thus confirming the exceptional quality of the site above it.

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“…Alternatively, fast sonic anemometers can provide the instantaneous air temperature, which can be used to calculate turbulence. Sonic anemometers are generally robust, but are expensive and difficult to keep ice-free, and are more suitable for permanent installations (Travouillon et al 2008;Schöck et al 2009).…”

Section: Profiling Optical Turbulence In Antarcticamentioning

confidence: 99%

Thickness of the Atmospheric Boundary Layer Above Dome A, Antarctica, during 2009

Bonner¹,

Ashley²,

Cui³

et al. 2010

PUBL ASTRON SOC PAC

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The domes, or local elevation maxima, on the Antarctic plateau provide a unique opportunity for ground-based astronomy in that the turbulent boundary layer is so thin that a telescope on a small tower can be in the free atmosphere, i.e., the portion of the atmosphere in which the turbulence is decoupled from the effect of the Earth's surface. There, it can enjoy a free atmosphere which itself appears to offer superior conditions to that of temperate sites. This breaks the problem of characterizing the turbulence at Antarctic plateau sites into two separate tasks: determining the variability, distribution and thickness of the boundary layer, and characterizing the free atmosphere. In this article we tackle the first of these tasks using a high-resolution, low minimum sample height sonic radar (SODAR) called Snodar that has been specifically designed to characterize the Antarctic boundary thickness and structure. Snodar delivers a vertical resolution of 0.9 m, with a minimum sampling height of 8 m. Snodar sampled the first 180 m of the atmosphere with 0.9 m resolution every 10 s at Dome A, Antarctica between 2009 February 4 and 2009 August 18. The median thickness of the boundary layer over this period was 13.9 m, with the 25th and 75th percentiles at 9.7 m and 19.7 m, respectively. The data collected from Dome A also show that, while the boundary layer can be stable for several hundred hours at a time, it can also be highly variable and must be sampled on the time scale of minutes to properly characterize its thickness.

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Sampling the ground layer of the atmosphere at Dome C using fast sonic-anemometers

Cited by 9 publications

References 4 publications

Dome C Site Characterization in 2006 with Single-Star SCIDAR

Dome C Site Characterization in 2006 with Single-Star SCIDAR

Dome C site testing: surface layer, free atmosphere seeing, and isoplanatic angle statistics

Thickness of the Atmospheric Boundary Layer Above Dome A, Antarctica, during 2009

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