gome-2 fm3 (metop-a) instrument review, eumetsat, darmstadt, june 2012 slide: 1 rűdiger lang, rose...

GOME-2 FM3 (Metop-A) Instrument Review, EUMETSAT, Darmstadt, June 2012 Slide: 1

Rűdiger Lang, Rose Munro, Antoine Lacan, Richard Dyer, Marcel Dobber, Christian Retscher, Gabriele Poli, and Michael Grzegorski EUMETSAT

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

On-ground versus On-Board modelling


AIRRWhat is the AIRR

elevation

Azi

mu

th

On-ground In-Orbit

elevation

Azi

mu

th

Se

as

on

Daily Sun Meas. Sequence

Instrument set-up layout, courtesy: TNO


AIRRWhat is the AIRR

elevation

Azi

mu

th

On-ground

Discretisation Settings:On-ground results (example):

Instrument set-up layout, courtesy: TNO

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)


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


AIRRSpecifications for FM-3/PGS 7 – Angle grid

PGS 7 page 87


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 gridInterpolated 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.


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


AIRRDisclaimer

1. Sorry! Its a 4D problem (I, ,j e,l)!

2. All results are preliminary awaiting approval by level-2 retrievals!


AIRR – The angular resolution problemMeasurements at FM3/Metop-A key-data elevation grid – operational setup

Band 3 at 420 nm

On-boardElevation:

FM3 situation !


AIRR – The angular resolution problem Measurements at high res. fixed elevation grid – offline setup

Band 3 at 420 nm

On-BoardElevation:

High- resolution/FM-2situation !


AIRR – The angular resolution problem Comparison between current key-data and high res. elevation angle grid

Elevation:Key-data – FM3 setup

Elevation:OnBoard – High resolution/FM2 setup

Band 3 at 420 nm


AIRR – derived from 2007Measurements at high res. fixed azimuth grid – offline setup without de-trending

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!

Year 2007


AIRR – derived from 2010/11Measurements at high res. fixed azimuth grid – offline setup without de-trending

Band 3 at 420 nm

Azimuth:On-Board

Less zigzag because of smaller degradation rate throughout the year 2010/11!

Year June 2010-June 2011


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


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]


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


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


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!


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


AIRRResults for detrended high-resolution AIRR from GOME-2 measurments 2010/2011

Band 3 at 420 nm

On-BoardElevation:

High- resolution/FM-2situation !


AIRRResults for detrended high-resolution AIRR from GOME-2 measurments 2010/2011

Band 3 at 420 nm

On-BoardAzimuth:

High- Resolution (recommended)


AIRR – Results On-Ground VS On-BoardSimulated and key-data derived MME1,irr

Band 3 at 420 nm

From key-data

Simulated from 1 year of solar measurements2010/2011

On-ground vs.On-BoardAzimuth/elevation:

High- Resolution 0.5/0.1 degrees


AIRR – Results On-Ground VS On-BoardSimulated and key-data derived MME1,irr

Channel 3

From key-data

Simulated from 1 year of solar measurements2010/2011

On-ground vs.On-Board

Relative toElevation = 0


AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference spectra

17th October 2007

On-ground On-board – New AIRR


AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference spectra

17th October 2007

On-ground vs.On-BoardderivedAIRR

Impact on SMR main channel data


AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference PMD spectra

17th October 2007


Impact on SMR PMD P-to-S ratio data


AIRRApplication of modelled AIRR (de-trended) to Solar Mean Reference PMD spectraImpact on level 2 (preliminary!)17th October 2007


Impact on ozone total column using GDOAS(Courtesy: O3MSAF/BIRA)

O3 (new AIRR) – O3 (FM3 key-data) [%]




Impact on NO2 total column using GDOAS(Courtesy: O3MSAF/BIRA)

NO2 (new AIRR) – NO2 (FM3 key-data) [%]




Impact on NO2 total column using GDOAS(Courtesy: O3MSAF/BIRA)

BrO (new AIRR) – BrO (FM3 key-data) [%]


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: 1. To measure the AIRR on-ground on a 0.5 resolution grid for

SAA and on a 0.1 resolution grid for elevation angle.

2. To smooth the data in spectral space and to improve on removal of “etalon-type” wiggles.


AIRRConclusions and Recommendations

The end


NOAA results by Larry Flynn (41st GSAG)

EAST

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|<5Lon<-100

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gome-2 fm3 (metop-a) instrument review, eumetsat, darmstadt, june 2012 slide: 1 rűdiger lang, rose...

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