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GOME-2 AIRR: Angular dependence of the GOME-2 solar irradiance (AIRR )

GOME-2 AIRR: Angular dependence of the GOME-2 solar irradiance (AIRR ) On-ground versus On-Board modelling. Rűdiger Lang, Rose Munro, Antoine Lacan, Richard Dyer, Marcel Dobber, Christian Retscher, Gabriele Poli, and Michael Grzegorski EUMETSAT. AIRR What is the AIRR.

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GOME-2 AIRR: Angular dependence of the GOME-2 solar irradiance (AIRR )

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  1. GOME-2 AIRR:Angular dependence of the GOME-2 solar irradiance (AIRR) On-ground versus On-Board modelling Rűdiger Lang, Rose Munro, Antoine Lacan, Richard Dyer, Marcel Dobber, Christian Retscher, Gabriele Poli, and Michael Grzegorski EUMETSAT

  2. AIRRWhat is the AIRR Instrument set-up layout, courtesy: TNO On-ground In-Orbit Azimuth Azimuth Season elevation elevation Daily Sun Meas. Sequence

  3. AIRRWhat is the AIRR On-ground results (example): Discretisation Settings: On-ground FM3: Azimuth: 5 degrees (-317 to 333) Elevation: 0.75 degrees (-1.5 to 1.5) FM2: Azimuth: 2 degrees (-316.3 to 333.3) Elevation: 0.1 degrees (-1.5 to 1.5) Azimuth elevation Instrument set-up layout, courtesy: TNO

  4. AIRRSpecifications for FM-3/PGS 7 – Key-data for MME1,irr PGS 7 page 96 and A.2.0.4 (page 75) RA_ABS_IRR_MAIN.203 BSDF_AIRR.203

  5. AIRRSpecifications for FM-3/PGS 7 – Angle grid PGS 7 page 87

  6. AIRRSimulation set-up Offline simulation of AIRR using EUM and FM2, as well as high resolution settings: • High res. elevation grid (all): -1.5 to +1.5 at 0.1 degrees fixed grid • Interpolated per individual solar measurement period from real elevation grid • Medium res. FM2 SAA grid: 316.7 to 333.3 at 2 degrees grid (c.f. 5 degrees for FM3) • Interpolated from all 365 solar measurements between June 2010 and June 2011. • High res. SAA grid: 316.7 to 333.3 at 0.5 degrees grid (c.f. 5 degrees for FM3) • Interpolated from all 365 solar measurements between June 2010 and June 2011. • AIRR ( C (j,e) ) is derived from raw calibrated signals and offline corrected for Dark current, normalised per integration time, Etalon, and PPG such that: • C (j,e) = SDNEP(j,e) / SDNEP (j=325,e=0) • For cross-checking the same is done with “half-calibrated spectra” SDNSE(j,e)/Mirr,1 and compared to original PPF-L1B data.

  7. AIRRSimulation reference period Reference period has been shifted from 2007 (previous analysis) to June 2010-June 2011 2010/11 provides a much more quieter period (no instrument anomalies or switch-offs) with smaller degradation rate and better consistence between main channels and PMD

  8. AIRRDisclaimer Sorry! Its a 4D problem (I,j,e,l)! All results are preliminary awaiting approval by level-2 retrievals!

  9. AIRR – The angular resolution problemMeasurements at FM3/Metop-A key-data elevation grid – operational setup Band 3 at 420 nm On-board Elevation: FM3 situation !

  10. AIRR – The angular resolution problem Measurements at high res. fixed elevation grid – offline setup Band 3 at 420 nm On-Board Elevation: High- resolution/FM-2 situation !

  11. AIRR – The angular resolution problem Comparison between current key-data and high res. elevation angle grid Band 3 at 420 nm Elevation: Key-data – FM3 setup Elevation: OnBoard – High resolution/FM2 setup

  12. AIRR – derived from 2007Measurements at high res. fixed azimuth grid – offline setup without de-trending Year 2007 Band 3 at 420 nm Azimuth: On-Board The zigzag features are the results of continuous degradation in combination with different SAA measured at different times throughout the year!

  13. AIRR – derived from 2010/11Measurements at high res. fixed azimuth grid – offline setup without de-trending Year June 2010- June 2011 Band 3 at 420 nm Azimuth: On-Board Less zigzag because of smaller degradation rate throughout the year 2010/11!

  14. AIRRDe-trending of results during 2011 – Band 3 / Channel 3 • Signals are de-trended subtracting a simple (robust) linear gradient. • June 2007 is used as reference point • Previously the year 2007 was used which a much less stable situation and non-linear degradation -> introduction of lots of artefacts in the de-trending

  15. AIRRDe-trending of results during 2011 – Band 3 / Channel 3 • Signals are de-trended subtracting a simple (robust) linear gradient. • June 2007 is used as reference point • Previously the year 2007 was used which a much less stable situation and non-linear degradation -> introduction of lots of artefacts in the de-trending [ show results per wavelength for de-trending]

  16. AIRRMeasurements at FM-2 2.0 degree azimuth grid – offline setup de-trended Band 3 at 420 nm Azimuth: On-Board De-trended signals for June 2010 to June 2011 at FM2-2 campaign resolution of 2.0 degrees for SAA June 2010 to June 2011

  17. AIRRMeasurements at High. Res. 0.5 degree azimuth grid – offline setup de-trended Band 3 at 420 nm Azimuth: On-Board De-trended signals for June 2010 to June 2011 at FM2-2 campaign resolution of 2.0 degrees for SAA June 2010 to June 2011

  18. AIRR – Recommendation for future CampaignsAIRR simulation at different resolutions – Band 3 SAA: 0.5 resolution (317 to 333) Elevation: 0.1 resolution (-1.5 to 1.5) Similar to L1-processor angle fine-grid as defined in initialisation file! Better discretisation balance!

  19. AIRRFM2 calibration campaign settings – FM2 /Metop-B key-data set • For the FM2-2 calibration campaign the following settings have been implemented: • SAA: 2 degree resolution (316.7, 317 to 333, 333.3) • Elevation: 0.1 degree resolution (-1.5 to 1.5) • The recommended SAA resolution of 0.5 degrees could not be implemented because of time and stability constraints. • This has been regarded as an acceptable compromise between time constraints and expected accuracy at the point of the decision in February 2011 (considering the lower frequency structures observed in SAA) • For the future the measurement at 0.5 degrees is highly recommended

  20. AIRRResults for detrended high-resolution AIRR from GOME-2 measurments 2010/2011 Band 3 at 420 nm On-Board Elevation: High- resolution/FM-2 situation !

  21. AIRRResults for detrended high-resolution AIRR from GOME-2 measurments 2010/2011 Band 3 at 420 nm On-Board Azimuth: High- Resolution (recommended)

  22. AIRR – Results On-Ground VS On-BoardSimulated and key-data derived MME1,irr From key-data Band 3 at 420 nm On-ground vs. On-Board Azimuth/ elevation: High- Resolution 0.5/0.1 degrees Simulated from 1 year of solar measurements 2010/2011

  23. AIRR – Results On-Ground VS On-BoardSimulated and key-data derived MME1,irr Simulated from 1 year of solar measurements 2010/2011 Channel 3 On-ground vs. On-Board Relative to Elevation = 0 From key-data

  24. AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference spectra 17th October 2007 On-ground On-board – New AIRR

  25. AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference spectra 17th October 2007 On-ground vs. On-Board derived AIRR Impact on SMR main channel data

  26. AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference PMD spectra 17th October 2007 On-ground vs. On-Board derived AIRR Impact on SMR PMD P-to-S ratio data

  27. AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference PMD spectraImpact on level 2 (preliminary!) 17th October 2007 On-ground vs. On-Board derived AIRR Impact on ozone total column using GDOAS (Courtesy: O3MSAF/ BIRA) O3 (new AIRR) – O3 (FM3 key-data) [%]

  28. AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference PMD spectraImpact on level 2 (preliminary!) 17th October 2007 On-ground vs. On-Board derived AIRR Impact on NO2 total column using GDOAS (Courtesy: O3MSAF/ BIRA) NO2 (new AIRR) – NO2 (FM3 key-data) [%]

  29. AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference PMD spectraImpact on level 2 (preliminary!) 17th October 2007 On-ground vs. On-Board derived AIRR Impact on NO2 total column using GDOAS (Courtesy: O3MSAF/ BIRA) BrO (new AIRR) – BrO (FM3 key-data) [%]

  30. AIRRConclusions and Recommendations Overall: The impact of the difference between in-orbit modelled AIRR and the one that has been delivered in the key-data on the mean solar reference spectrum is small. But the spectral features are probably non-negligible and the impact may be different at various times per year (not fully investigated yet!). Preliminary: The impact on level-2 retrievals varies with the significance of the spectral features. Impact on TO3 is small whereas the impact on TNO2 and TBrO seems to be quite significant Recommendation: To measure the AIRR on-ground on a 0.5 resolution grid for SAA and on a 0.1 resolution grid for elevation angle. To smooth the data in spectral space and to improve on removal of “etalon-type” wiggles.

  31. AIRRConclusions and Recommendations The end

  32. NOAA results by Larry Flynn (41st GSAG) Version 8 331-nm Reflectivity for a box in the Equatorial Pacific. The unadjusted values in the top plot reach a minimum of 8% (higher than expected for the open ocean) for the Nadir scan position. A single calibration adjustment lowers this value to 4% and also flattens out the scan dependence for West-viewing positions. The East-viewing results are not as good. |Lat|<5 Lon<-100 EAST WEST

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