Page 1GHRSST-PP 8th Science Team Meeting, Melbourne, 18th May 2007

ATSR-2/AATSR Overlap Analysis

Gary Corlett

AATSR Validation Scientist

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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

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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