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An Update on AIRS Validation Activities at Dome Concordia, Antarctica

Von P. Walden, Brad Halter, Lance Roth, U. Idaho Bob Stone, NOAA-CMDL Dave Tobin, U. Wisconsin 31 March 2004 AIRS Science Team Meeting Greenbelt, MD. An Update on AIRS Validation Activities at Dome Concordia, Antarctica. Validation Goals. Radiance validation T and H 2 O profiles

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An Update on AIRS Validation Activities at Dome Concordia, Antarctica

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  1. Von P. Walden, Brad Halter, Lance Roth, U. Idaho Bob Stone, NOAA-CMDL Dave Tobin, U. Wisconsin 31 March 2004 AIRS Science Team Meeting Greenbelt, MD An Update on AIRS Validation Activities at Dome Concordia, Antarctica

  2. Validation Goals • Radiance validation • T and H2O profiles • Surface Emissivity (snow) • Cloud properties

  3. Dome Concordia • French / Italian station • 75 S, 123 E • Currently a “summer station”, but first winter-over will be next year in 2005.

  4. Field Seasons • Data Acquistion Periods: • 13 January 2003 – 29 January 2003 • 15 Dec 2003 – 29 January 2004

  5. Aqua Overpass Summary Jan 2003 Dec 2003/Jan 2004 Total 106 287 Near-nadir 35 83 Clear sky 18 73

  6. Instruments • Polar Atmospheric Emitted Radiance Interferometer (PAERI) • Spectral IR radiances of sky and surface • Calibrated to within 0.05 K at -20 C (253 K) • Infrared Radiometric Thermometer (IRT) • Bobsled (for Bob Stone) • Also, operate at times from 32-meter tower • Inter-calibrated frequently to SSEC BB in the field • Vaisala RS90 and RS80 radiosondes • 60 RS90 sondes used primarily under clear skies • Total column ozone

  7. PAERI • Results from 2002-2003 • PAERI measured large temperature differences (»2 K) over small spatial scales of 2 to 4 feet. (PAERI ground FOV was 1- foot diameter) • Also, large diurnal cycle of 15 to 20 K under clear skies. • Improvements made in 2003-2004 • Raised PAERI from 6 meters to 25 meters above the snow surface. • Increased temporal and spatial sampling of the surface. • RESULT: • PAERI ground FOV increased from about 1-foot diameter to about 4 feet by 30 feet. • Better resolution of diurnal cycle.

  8. Polar AERI = Highest AERI Approx. PAERI ground FOV 25 meters

  9. Snow Surface Roughness

  10. The Bobsled • Two main tests • 1-, 3-, and 5-km triangular tracks (in 1 hour or less) • “Static” sastrugi tests (to map T vs. roughness) • Large area “temperature maps” from top of 32-m tower

  11. KT19 “Temperature Maps” from Tower 0.25 km • Not much azimuthal angle dependence • Mean T = - 22.5 C • Std dev = - 0.4 C (some of which is due to the zenith dep. of e)

  12. Preliminary Bobsled Results

  13. Radiosonde Profiles

  14. Total Column Ozone

  15. Radiance Validation • Methodology • Create model atmosphere using radiosonde data. • Derive Ts and  from PAERI data. • Run kcarta --> TOA radiances at AIRS resolution. • Compare AIRS obs – TOA calcs.

  16. Radiance Validation 23 Dec 2003, 0846 GMT, 1646 local

  17. Radiance Validation 27 Dec 2003, 0821 GMT, 1621 local

  18. Radiance Validation 12 Jan 2004, 1451 GMT, 2251 local

  19. Radiance Validation 14 Jan 2004, 1438 GMT, 2238 local

  20. Radiance Validation 27 Dec 2003, 1451 GMT, 2251 local

  21. Radiance Validation 15 Jan 2004, 0714 GMT, 1514 local

  22. Radiance Validation • Summary • Most preliminary comparisons fall within +0.5 K. • However, a few have large differences. • Many more cases to look at in the near future.

  23. Temperature Profile Checks

  24. Temperature Profile Checks

  25. Emissivity Check • AIRS retrievals (from Susskind January 2003): • Values are too low. • Spectral features are slightly shifted to small wavenumbers.

  26. CO and O3 Retrievals (near future) • With Wallace McMillan and Kurt Lightner

  27. Cloud Properties (near future) • Cloud base, optical depth, and effective particle size retrievals using Mahesh et al (2001).

  28. Conclusions • Preliminary radiance validation using data from Dec 2003/Jan 2004 shows decent agreement between PAERI-derived TOA radiances and raw AIRS radiances. • Spot check on temperature profiles from January 2003 look quite good. • Spot check on emissivity retrievals of snow show that the AIRS retrieved values are too low and have a spectral shift toward low wavenumbers.

  29. Future Work • Future (summer/fall 2004) • Adding more cases to radiance validation • Temperature and humidity comparisons • Emissivity validation with more cases • Carbon monoxide and ozone retrievals (with Wallace McMillan) • Derive cloud properties using Mahesh et al (2001)

  30. Derivation of H2O Continuum • Two separate experiments performed at South Pole and Dome C show temperature dependence similar to that suggested by Ma and Tipping negative positive

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