1. Page 1Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research Preliminary validation of the first SCIAMACHY CH 4 and CO measurements Authors: A.G. Straume, I. Aben (PI), A.N. Maurellis, H. Schrijver (SRON), M. Krol (IMAU), H. Eskes, J.F. Meirink, M. van Weele (KNMI), J. Gille (NCAR)

2. Page 2Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research COMETH, AOID241  Comparison of the operational CO and CH 4 products (P oper ) with an SRON retrieved product  Comparison with measurements by the MOPITT instrument (cooperation with NCAR)  Comparison of P oper with calculations by the chemical transport model TM5 (cooperation with IMAU)  Will use data assimilation for extended validation and analysis (cooperation with KNMI)

3. Page 3Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research Status of the SCIAMACHY near-infrared channels  The SCIAMACHY instrument is stable. Only anomaly:  Ice build-up in NIR channels 7 and 8. The influence of the ice is relatively smooth. Main effect: reduced Signal-to-Noise ratio. Problem solver: frequent decontamination.  Updates needed with respect to the on-ground calibration:  Dead and bad pixel mask  Wavelength calibration of channel 8  Change in frequency of updating calibration annotation data due to the ice buildup:  Channel 7 and 8 dark current must be updated (at least) once pr day  In verification orbits 2509 and 2510 (SW v. 4.00) the above mentioned updates to the L1b product were implemented

4. Page 4Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research BIAS retrieved CH 4 columns (two micro windows), orbits 2509-2510 23 August Micro window 1 (SW v. 4.0)Micro window 2 (SW v. 4.0)

5. Page 5Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research SW v. 4.0 BIAS CH 4 columns compared to simulation by a chemical transport model (resolution 2.5  2.5  ) orbits 2509-2510 23 August

6. Page 6Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research BIAS CO columns (left) compared to MOPITT beta data (right) orbits 2509-2510 23 August SW v 4.0

7. Page 7Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research Average surface elevation [m] PMD measurementsMethane columns [10 19 cm -2 ] 1,2 0,4 3,6 2,8 2,0 4,0 3,2 2,4 1,6 0,8 0 SRON retrieved CH 4 columns, orbits 2337-2338 11 August orbits 2337-2338 11 August

8. Page 8Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research Non-clouded pixels only and error bars representing the measurement error # comparisons: 681 BIAS: 24% RMSD: 26% Correlation: 0.4 (99% significant) SRON retrieved CH 4 columns v.s. topography (left), v.s. simulation by a chemical transport model with resolution 2.5  2.5  (right) Non-clouded pixels only. NB! The SCIAMACHY CH 4 columns are here NOT binned to the model resolution, i.e. an artificially large spread (bias) is seen

9. Page 9Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research SRON retrieved CO compared with CO from MOPITT (beta data), orbits 2337-2338 The CO signal is still below the systematic residuals and the instrument noise, giving erroneously low or 0 column values

10. Page 10Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research CONCLUSIONS  The BIAS product is not correct (suspects: calibration, L1-2 processor,...)  The SRON retrieved CH 4 product looks promising and shows physically consistent variations. Still bias of ~15% (too low) probably related to still unresolved calibration issues  The CO signal is still below the systematic residuals and the instrument noise. A comparison with MOPITT data shows that it is ~50% too low  Still unresolved calibration issues, channel 8: variations with time in the dark current signal, pixel-to-pixel gain (PPG),...

11. Page 11Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research Figure: Courtesy of Louisa Emmonds, NCAR

12. Page 12Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research BIAS_2 retrieved CH4 columns and SRON PMD image, orbits 2509-2510 23 August SW v 4.0

13. Page 13Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research SRON retrieved CH 4 and CH 4 error v.s. albedo, orbits 2337-2338 11 August Cloud-free pixels only

14. Page 14Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research Cloud-free CH 4 columns compared with model (including measurement errors) and CH 4 errors v.s. albedo Non-clouded pixels only. NB! The SCIAMACHY CH 4 columns are here NOT binned to the model resolution, i.e. an artificially large spread (bias) is seen

15. Page 15Validation by Satellite Intercomparison - ESRIN 9–13 December 2002 National Institute for Space Research SCIAMACHY channel 8 residuals Residuals between the measured and a modelled spectrum for different albedos: Black and red: residuals during high albedo cases (desert). Blue: residuals during a low albedo case (boulders).