scholarly journals Adaptive Optics and Interferometry on the Antarctic Plateau

2005 ◽  
Vol 13 ◽  
pp. 960-961
Author(s):  
James P. Lloyd
Keyword(s):  
Adaptive Optics ◽  
Coherence Time ◽  
Field Of View ◽  
Turbulent Layer ◽  
Antarctic Plateau ◽  
Useful Field Of View ◽  
Low Wind Speed ◽  
Visible Wavelengths ◽  
Sodar Measurements ◽  
The Antarctic

AbstractThe unique properties of atmospheric turbulence in atmosphere above the Antarctic plateau offer some compelling advantages for astronomical adaptive optics and interferometry. The shallow nature of the turbulent layer at the South Pole results in low scintillation and large angular coherence (Marks et al. 1996, 1999; Lloyd, Oppenheimer, & Graham 2002; Lloyd et al. 2003). Recent wintertime SODAR measurements at Dome C indicate that similar conditions exist at Dome C, but that the turbulent layer is likely both weaker and shallower. This paper discusses the outcomes of such conditions on the atmospheric properties for astronomy. Particularly due to the low wind speed at Dome C, the atmospheric properties are highly favorable for adaptive optics and interferometry. The resulting long coherence time enables adaptive optics at visible wavelengths, and the large angular coherence results in a useful field of view as a result.

scholarly journals Extremely Large Telescopes on the Antarctic plateau

2005 ◽  
Vol 13 ◽  
pp. 956-957
Author(s):  
J.S. Lawrence
Keyword(s):  
Adaptive Optics ◽  
Turbulence Structure ◽  
Large Telescope ◽  
Dome A ◽  
Antarctic Plateau ◽  
Guide Star ◽  
Laser Guide ◽  
Large Telescopes ◽  
The Antarctic ◽  
Adaptive Optics System

AbstractThe primary limitation to the performance of any large ground-based telescope is the atmospheric properties of its site, particularly the sky emission and the turbulence structure. There are several sites on the Antarctic plateau (South Pole, Dome C and Dome A) for which the increase in infrared sensitivity relative to a mid-latitude site should be as much as two orders of magnitude. The unique turbulent structure above Dome C indicates that an extremely large telescope equipped with only a natural guide star adaptive optics system should achieve equivalent resolution to a mid-latitude extremely large telescope with a multi-conjugate multi-laser guide star system.

Increasing the useful field of view of an adaptive optics system

1998 ◽  
Author(s):  
Mark R. Chun ◽  
Walter J. Wild ◽  
Fang Shi ◽  
Michael F. Smutko ◽  
Edward J. Kibblewhite ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Field Of View ◽  
Useful Field Of View ◽  
Adaptive Optics System

scholarly journals Atmospheric Temperature Measurement Biases on the Antarctic Plateau

2011 ◽  
Vol 28 (12) ◽  
pp. 1598-1605 ◽  
Author(s):  
Christophe Genthon ◽  
Delphine Six ◽  
Vincent Favier ◽  
Matthew Lazzara ◽  
Linda Keller
Keyword(s):  
Wind Speed ◽  
Solar Radiation ◽  
Strong Dependence ◽  
High Surface ◽  
Atmospheric Temperature ◽  
Antarctic Plateau ◽  
Low Wind Speed ◽  
Measurement Biases ◽  
The Cost ◽  
The Antarctic

Abstract Observations of atmospheric temperature made on the Antarctic Plateau with thermistors housed in naturally (wind) ventilated radiation shields are shown to be significantly warm biased by solar radiation. High incoming solar flux and high surface albedo result in radiation biases in Gill (multiplate)-styled shields that can occasionally exceed 10°C in summer in cases with low wind speed. Although stronger and more frequent when incoming solar radiation is high, biases exceeding 8°C are found even when solar radiation is less than 200 W m−2. Compared with sonic thermometers, which are not affected by radiation but are too complex to be routinely used for mean temperature monitoring, commercially available aspirated shields are shown to efficiently protect thermistor measurements from solar radiation biases. Most of the available in situ reports of atmospheric temperature on the Antarctic Plateau are from automatic weather stations that use passive shields and are thus likely warm biased in the summer. In spite of low power consumption, deploying aspirated shields at remote locations in such a difficult environment may be a challenge. Bias correction formulas are not easily derived and are obviously shield dependent. On the other hand, because of a strong dependence of bias to wind speed, filtering out temperature reports for wind speed less than a given threshold (about 4–6 m s−1 for the shields tested here) may be an efficient way to quality control the data, albeit at the cost of significant data loss and records that are biased toward high wind speed cases.

Estimation of turbulent heat fluxes and exchange coefficients for heat at Dumont d'Urville, East Antarctica

1999 ◽  
Vol 11 (1) ◽  
pp. 93-99 ◽  
Author(s):  
S. Argentini ◽  
G. Mastrantonio ◽  
A. Viola
Keyword(s):  
Boundary Layer ◽  
Heat Fluxes ◽  
East Antarctica ◽  
Turbulent Heat ◽  
Convective Boundary ◽  
Doppler Sodar ◽  
Turbulent Heat Fluxes ◽  
Unstable Boundary Layer ◽  
Sodar Measurements ◽  
The Antarctic

Simultaneous acoustic Doppler sodar and tethersonde measurements were used to study some of the characteristics of the unstable boundary layer at Dumont d'Urville, Adélie Land, East Antarctica during the summer 1993–94. A description of the convective boundary layer and its behaviour in connection with the wind regime is given along with the frequency distribution of free convection episodes. The surface heat flux has been evaluated using the vertical velocity variance derived from sodar measurements. The turbulent exchange coefficients, estimated by coupling sodar and tethered balloon measurements, are in strong agreement with those present in literature for the Antarctic regions.

scholarly journals The growth of sublimation crystals and surface hoar on the Antarctic plateau

2014 ◽  
Vol 8 (4) ◽  
pp. 1205-1215 ◽  
Author(s):  
J.-C. Gallet ◽  
F. Domine ◽  
J. Savarino ◽  
M. Dumont ◽  
E. Brun
Keyword(s):  
Energy Budget ◽  
Temperature Drop ◽  
Snow Surface ◽  
Surface Mass ◽  
Antarctic Plateau ◽  
Time Variations ◽  
Sunny Weather ◽  
Frost Flowers ◽  
Snow Model ◽  
The Antarctic

Abstract. On the Antarctic plateau, precipitation quantities are so low that the surface mass budget is for an important part determined by exchanges of water vapor between the snow surface and the atmosphere surface. At Dome C (75° S, 123° E), we have frequently observed the growth of crystals on the snow surface under calm sunny weather. Here we present the time variations of specific surface area (SSA) and density of these crystals. Using the detailed snow model Crocus, we conclude that the formation of these crystals was very likely due to the nighttime formation of surface hoar crystals and to the daytime formation of sublimation crystals. These latter crystals form by processes similar to those involved in the formation of frost flowers on young sea ice. The formation of these crystals impacts the albedo, mass and energy budget of the Antarctic plateau. In particular, the SSA variations of the surface layer can induce an instantaneous forcing at the snow surface up to −10 W m−2 at noon, resulting in a surface temperature drop of 0.45 K. This result confirms that snow SSA is a crucial variable to consider in the energy budget and climate of snow-covered surfaces.

Sign in / Sign up

Export Citation Format

Share Document