June 8, 2004

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An Analysis of Surface Wind Speeds at Dome C,
Antarctica

• C. Meyer and J.W.V. Storey
• School of Physics/Univ. of New South Wales
• Presented on their behalf by Shelley L. Knuth
• Antarctic Meteorological Research Center

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Outline

• Introduction/Purpose
• Dome C and Astronomy
• Results
• Conclusion

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Introduction/Purpose

• AWS/AMRC project assists many scientists in other
  fields
• Provided twenty years worth of data from Dome C

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Introduction (Cont.)

• Wind speeds important to deployment of telescopes
• Telescopes have to survive higher winds cause
  more stress on telescopes, especially the ELTs
• Wind loads must not deform mirrors by more than a
  few tens of nm. moves less with lower wind
  speeds
• High wind speeds create turbulent ground layer
  and reduce telescope resolution.
• Low wind speeds increase time available to focus
  on a Guide Star which allows for fainter stars to
  be used

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Introduction (ctd.)

• Longer exposure allows you to "see" farther out
  into space without having the view distorted by
  turbulence (sort of like the heat shimmer that
  comes off the pavement on a hot day).
• High wind speeds result in higher dust or ice
  crystal levels, which reduce the operational
  abilities of the telescope
• Ground layer only turbulence in the atmosphere so
  allows unprecedented image quality over a wide
  field

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Dome C and Astronomy

• Lat/Lon (ca. 1980) 74.5S, 123.00E, 3280m and
  (ca. 1995) 75.12S, 123.37E, 3250m
• Exceptionally low wind speeds because high on
  plateau and are just starting their flow down the
  mountains
• Thin boundary layer
• Excellent place for an astronomical observatory

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Dr. Anna Moore of the Anglo-Australian Observatory
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(No Transcript)
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Results
Mean monthly wind speed at Dome C and Dome C II
from the beginning of 1984 to the end of 2003.
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Figure 2. Wind rose, showing the probability that
the wind will be of a particular speed and in a
particular direction, for Dome C and Dome C II
combined, for the same period as in Figure 1.
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Table 1. Mean wind speeds at Dome C and at other
astronomical sites for which long-term data
exist.
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Figure 4. Probability histogram for 1990 showing
all data (top panel), winter months (middle
panel), and astronomical darkness (lower panel).
Also shown is the cumulative probability.
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Figure 7. Probability histogram for 2003 showing
all data (top panel), winter months (middle
panel), and astronomical darkness (lower panel).
Also shown is the cumulative probability.
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Conclusions

• Dome C winds are very low
• Winds many times are even null
• Incredible advantage for telescope designers
• Good place for the new Extremely Large Telescope
  and proposed Antarctic Planet Interferometer

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Acknowledgments

• Linda Keller AWS Data
• Peter Gillingham, Panayiotis Tzanavaris, and Jon
  Everett at UNSW
• Support from Australian Research Council

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Figure 3. Probability histogram for 1984 showing
all data (top panel), winter months (middle
panel), and astronomical darkness (lower panel).
Also shown is the cumulative probability.
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Figure 5. Probability histogram for 1996 showing
all data (top panel), winter months (middle
panel), and astronomical darkness (lower panel).
Also shown is the cumulative probability.
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Figure 6. Probability histogram for 2002 showing
all data (top panel), winter months (middle
panel), and astronomical darkness (lower panel).
Also shown is the cumulative probability.