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ATSR2/AATSR Validation Results at Lake Tahoe CA/NV, USA

ATSR2/AATSR Validation Results at Lake Tahoe CA/NV, USA. Hook, S. J., F. J. Prata, A. Abtahi, R. E. Alley, R.. C. Richards and S. G. Schladow. Outline. Review of Validation Activities Location Site Characteristics In situ measurements Reductions and analysis of in situ data. Results

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ATSR2/AATSR Validation Results at Lake Tahoe CA/NV, USA

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  1. ATSR2/AATSR Validation Results at Lake Tahoe CA/NV, USA Hook, S. J., F. J. Prata, A. Abtahi, R. E. Alley, R.. C. Richards and S. G. Schladow

  2. Outline • Review of Validation Activities • Location • Site Characteristics • In situ measurements • Reductions and analysis of in situ data. • Results • Typical Dataset: ASTER • ATSR2/AATSR validation and cross validation. • Future validation work into 2003 and beyond. • Conclusions/Summary

  3. Site Location

  4. Site Characteristics • High (low water vapor) • Large (validate a variety of satellite pixels sizes) • Homogenous (water, best target for thermal infrared validation) • Does not freeze (available year round) • Freshwater (equipment survivability) • Wide temperature range (~5-25 C) • Accessible (lower maintenance costs)

  5. Instrument Sites Water and Land

  6. Measurements at each Buoy

  7. Total Sky Imager (TSI) and Shadowband Radiometer above Tahoe Gauging Station at US Coast Guard.

  8. Data Reduction: Methodology For Radiance at Sensor Validation • Extract the bulk temperatures. • Extract the radiometric temperature. • Correct the radiometric temperature to skin kinetic temperature. • Propagate the skin temperature to the satellite using a radiative transfer model and interpolated atmospheric profile. • Convolve the propagated at-sensor radiance to the instrument response function to obtain the Vicarious Radiance (VR). • Extract the image radiance derived using the On Board calibrator (OBC). • Compare and contrast the OBC and VR Radiance values.

  9. Sensitivity Analysis for Correction of Radiometric Temperature to Skin Temperature

  10. Results • Thermal Infrared validation results are available for several spaceborne instruments for 2001/2002 using the Lake Tahoe CA/NV automated validation site. These include: • Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER). • Moderate Resolution Imaging Spectroradiometer (MODIS). • Landsat 5 and Landsat ETM+. • Multispectral Thermal Imager (MTI). • No results are presently available for ATSR2/AATSR since data have only become available in last few weeks.

  11. Example validation results for the Advanced Spaceborne Thermal Reflectance and Emission Radiometer (ASTER)

  12. In Flight Validation Accuracy of MOD02 and ASTER1B Products for Mission Thus Far

  13. ATSR2/AATSR Results • 10/04/2002 Notified ATSR2 scenes available for overlap period. • 11/04/2002 Notified 14 AATSR L1b scenes available download. • 11/19/2002 Notified additional 6 L1b scenes available for download. • 11/20/2002 Notified 1 L2 GST product available for download. • Based on previous years expect ~60 clear scenes between March and August (day and night). Each scene includes ~3 matchups so expect ~180 matchups for March-August.

  14. Preliminary Cloud Assement for 20 scenes

  15. ATSR2/AATSR Issues • ATSR2 Large discrepencies in forward and nadir images if attempt to geocode with embedded latitude/longitude arrays. Cannot automatically extract values over buoys from data. In order to extract data for validation will need to manually geocode each scene. • AATSR Issues • Problems downloading data from FTP site. Initial transfer fast then occasionally goes stale at ~30%. • 3 of scenes were “blank” empty. • Currently developing software in order to extract values at a specified latitude/longitude – does not appear possible with ENVIVIEW.

  16. Validation Beyond 2003 In order to provide a dataset suitable for long-term climate monitoring it is necessary to ensure the instrument and products remain calibrated and validated over the entire mission, not just a few months. In several cases, spaceborne instruments have been identified where the calibration drifts over time or software changes have resulted in changes in product accuracy. Current plans call for the continued calibration and validation of several EOS instruments and and products using Lake Tahoe. Strongly recommend validation continue for the duration of the ATSR mission at Lake Tahoe if available resources.

  17. Summary and Conclusions • Site is fully operational. • Data and products from several instruments currently being validated. • Validation of ATSR2/AATSR should begin soon. • FTP push and hard media delivery would help problems associated with data transfer.

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