page 1validation by satellite intercomparison - esrin 9–13 december 2002 national institute for...

Validation by Satellite Intercomparison - ESRIN 9–13 December 2002

National Institute for Space Research

Preliminary validation of the first Preliminary validation of the first SCIAMACHY CHSCIAMACHY CH44 and CO measurements 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)



COMETH, AOID241COMETH, AOID241

Comparison of the operational CO and CH4 products (Poper) with an SRON retrieved product

Comparison with measurements by the MOPITT instrument (cooperation with NCAR)

Comparison of Poper with calculations by the chemical transport model TM5 (cooperation with IMAU)

Will use data assimilation for extended validation and analysis (cooperation with KNMI)



Status of the SCIAMACHY near-infrared Status of the SCIAMACHY near-infrared channelschannels 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



BIAS retrieved CHBIAS retrieved CH44 columns (two micro columns (two micro windows), windows),

orbits orbits 2509-2510 2509-2510 23 August23 August

Micro window 1 (SW v. 4.0) Micro window 2 (SW v. 4.0)



SW v. 4.0

BIAS CHBIAS CH44 columns compared to simulation by columns compared to simulation by a chemical transport model (resolution a chemical transport model (resolution

2.52.52.52.5))orbits orbits 2509-2510 2509-2510 23 August23 August



BIAS CO columns (left) compared to MOPITT BIAS CO columns (left) compared to MOPITT beta data (right) orbits beta data (right) orbits 2509-25102509-2510 23 23

AugustAugust

SW v 4.0



Average surface elevation [m]PMD measurementsMethane columns [1019 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 CHSRON retrieved CH44 columns, columns, orbits 2337-2338 11 Augustorbits 2337-2338 11 August



Non-clouded pixels only and error barsrepresenting the measurement error

# comparisons: 681BIAS: 24%RMSD: 26%Correlation: 0.4 (99% significant)

SRON retrieved CHSRON retrieved CH44 columns v.s. topography columns v.s. topography (left), v.s. simulation by a chemical transport (left), v.s. simulation by a chemical transport

model with resolution 2.5model with resolution 2.52.52.5 (right) (right)

Non-clouded pixels only. NB! The SCIAMACHY CH4 columns are here NOT binned to the model resolution,

i.e. an artificially large spread (bias) is seen



SRON retrieved CO compared with CO from SRON retrieved CO compared with CO from MOPITT (beta data), orbits 2337-2338MOPITT (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



CONCLUSIONSCONCLUSIONS

The BIAS product is not correct (suspects: calibration, L1-2 processor, ...)

The SRON retrieved CH4 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), ...



Figure: Courtesy of Louisa Emmonds, NCAR



BIAS_2 retrieved CH4 columns and SRON BIAS_2 retrieved CH4 columns and SRON PMD image, orbits PMD image, orbits 2509-2510 2509-2510 23 August23 August

SW v 4.0



SRON retrieved CHSRON retrieved CH44 and CH and CH44 error v.s. error v.s. albedo, orbits 2337-2338 11 Augustalbedo, orbits 2337-2338 11 August

Cloud-free pixels only Cloud-free pixels only



Cloud-free CHCloud-free CH44 columns compared with model columns compared with model (including measurement errors) and CH(including measurement errors) and CH44 errors errors

v.s. albedov.s. albedo

Non-clouded pixels only. NB! The SCIAMACHY CH4 columns are here NOT binned to the model resolution,

i.e. an artificially large spread (bias) is seen



SCIAMACHY channel 8 residualsSCIAMACHY 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).

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