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Page 1 GHRSST-PP 8 th Science Team Meeting, Melbourne, 18 th May 2007 ATSR-2/AATSR Overlap Analysis Gary Corlett AATSR Validation Scientist
Page 1GHRSST-PP 8th Science Team Meeting, Melbourne, 18th May 2007
ATSR-2/AATSR Overlap Analysis
Gary Corlett
AATSR Validation Scientist
Page 2GHRSST-PP 8th Science Team Meeting, Melbourne, 18th May 2007
Spectral Profiles
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Simulated Bias: Centre of Swath
From Owen Embury (university of Edinburgh)
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Compare AATSR and ATSR-2 BTs: Case 1
Nadir View Forward View
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Compare AATSR and ATSR-2 BTs: Case 2
Nadir View Forward View
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Compare AATSR and ATSR-2 BTs: Case 2
Nadir View Forward View
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Effect of 12 micron BT offsetAATSR Skin AATSR Bulk
Match-ups N Bias St. Dev. % ±0.3 N Bias St. Dev. % ±0.3
Day D2 UC 43760 +0.08 0.33 N/A 39264 +0.24 0.32 55.82
Night D2 UC 47169 0.00 0.33 N/A 42742 +0.15 0.32 63.08
Night D3 UC 47198 0.00 0.26 N/A 42765 +0.16 0.24 71.87
Day D2 UC* 43759 -0.19 0.33 N/A 39264 -0.02 0.32 70.46
Night D2 UC* 47173 +0.09 0.33 N/A 42742 -0.11 0.32 65.92
Night D3 UC* 47198 -0.06 0.26 N/A 42766 +0.10 0.24 77.46
Match-up data from Anne O’Carroll (Met Office)
UC: December 2005 Case C coefficients; UC*: December 2005 Case C coefficients + 0.2 K added to all 12 micron BTs
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Correct AATSR or ATSR-2 ?
AATSR Bulk ATSR-2
Match-ups Bias (K) Bias (K)
Night D2 (A) -0.11 -0.09
Night D3 (A) +0.10 +0.10
Night D2 (B) +0.15 +0.20
Night D3 (B) +0.16 +0.16
Match-up data from Anne O’Carroll (Met Office)
A: +0.2 K offset applied to AATSR BTs B: -0.2 K offset applied to ATSR-2 BTs
Page 15GHRSST-PP 8th Science Team Meeting, Melbourne, 18th May 2007
Summary & Conclusions
Calibration offset seen between AATSR and ATSR-2 12 μm clear-sky sea BTs• ATS_MET_2P and AT2_MET_2P products analysed• Validation results suggest AATSR is incorrect• RAL to analyse flight-spare FPA
• Long-wavelength out-of-band leakage is suspected• Modelled by Dave Smith (RAL); to be tested by Edinburgh
The bottom line for GHRSST-PP users• D3 SST estimates are ~ + 0.05 K too warm
• Retrieval is dependant on 3.7 µm channel
• D2 SST estimates are ~ - 0.04 K too cold• Owing to opposite retrieval bias
• Will be factored into updated SSES
