Destriping of Viirs Modis Sst v2

Destriping of VIIRS and MODIS SST imageryDestriping of VIIRS and MODIS SST imagery

Marouan Bouali and Alexander IgnatovMarouan Bouali and Alexander Ignatov

NOAA/NESDIS/STAR and CSU/CIRANOAA/NESDIS/STAR and CSU/CIRA

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Workshop: “SST from polar orbiters: use of NWP models” Workshop: “SST from polar orbiters: use of NWP models” Centre de Météorologie Spatiale, Météo FranceCentre de Météorologie Spatiale, Météo France,, Lannion Lannion

March 5-7, 2013March 5-7, 2013

3/4/2013 Destriping VIIRS/MODIS SST

MotivationMotivationNative resolution SST imagery (≤1km) derived from whiskbroom Native resolution SST imagery (≤1km) derived from whiskbroom

scanners (MODIS, VIIRS) is affected with stripe noisescanners (MODIS, VIIRS) is affected with stripe noise

2Sea Surface Temperatures (°C)Sea Surface Temperatures (°C)

Destriping VIIRS/MODIS SSTDestriping VIIRS/MODIS SST

Terra MODISTerra MODIS Aqua MODISAqua MODIS NPP VIIRSNPP VIIRS

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T2012294110000.L2_LAC_SSTT2012294110000.L2_LAC_SST A2012294031500.L2_LAC_SSTA2012294031500.L2_LAC_SST ACSPO_V2.12_NPP_VIIRS_2012-10-20_1510-1519ACSPO_V2.12_NPP_VIIRS_2012-10-20_1510-1519

Accuracy of SST retrievalAccuracy of SST retrieval

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NPP VIIRS (0.75 km)NPP VIIRS (0.75 km)

Stripe noise in level 1B or SDRs BTsStripe noise in level 1B or SDRs BTscan lead to SST errors of up to ± 0.3Kcan lead to SST errors of up to ± 0.3K


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ACSPO_V2.12_NPP_VIIRS_2012-10-20_1510-1519ACSPO_V2.12_NPP_VIIRS_2012-10-20_1510-1519

SST FrontsSST Fronts

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NPP VIIRS (0.75 km)NPP VIIRS (0.75 km)

Sobel filterSobel filter

Striping introduces artificial structures and affects the analysis of Striping introduces artificial structures and affects the analysis of thermal fronts (orientation, intensity and location)thermal fronts (orientation, intensity and location)


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ACSPO_V2.12_NPP_VIIRS_2012-10-20_1840-1849ACSPO_V2.12_NPP_VIIRS_2012-10-20_1840-1849

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Prior to assimilating into UHR L4 SST,Prior to assimilating into UHR L4 SST,MODIS and VIIRS L2 SSTs should be destripedMODIS and VIIRS L2 SSTs should be destriped


UHR L4 SST will be increasingly used as input in NWP modelsUHR L4 SST will be increasingly used as input in NWP modelsdue to better weather prediction (LaCasse et al. 2008)due to better weather prediction (LaCasse et al. 2008)

ESA MEDSPIRATIONESA MEDSPIRATION

NASA JPL MURNASA JPL MURNASA JPL G1SSTNASA JPL G1SST

Ultra-High Resolution Level 4 SSTsUltra-High Resolution Level 4 SSTs

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Mitigation of stripingMitigation of striping

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Currently, blackbody (BB) and space view (SV) are used for Currently, blackbody (BB) and space view (SV) are used for absolute BT calibration on a scan-by-scan basisabsolute BT calibration on a scan-by-scan basis

This practice ensures that sensor uniformity performance is This practice ensures that sensor uniformity performance is within pre-launch specification within pre-launch specification BUTBUT it does not guarantee full it does not guarantee full mitigation of striping effectmitigation of striping effect

Post-processing of L1B (SDR) is required to generate improved Post-processing of L1B (SDR) is required to generate improved L1B, from which SST products with improved image quality can L1B, from which SST products with improved image quality can be producedbe produced


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Destriping LiteratureDestriping Literature

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~ 40 years of research (since Landsat MSS, 1972)~ 40 years of research (since Landsat MSS, 1972)

Techniques with potential for operational use are intended for Techniques with potential for operational use are intended for highly pronounced stripe noise whereas,highly pronounced stripe noise whereas,

Stripe noise in 11 & 12 µm bands (MODIS, VIIRS) is below 0.05 K..Stripe noise in 11 & 12 µm bands (MODIS, VIIRS) is below 0.05 K..

No work has been done so far for stripe noise reduction in SST No work has been done so far for stripe noise reduction in SST imagery other than…imagery other than…

Spatial smoothing of the atmospheric term in SST algorithmSpatial smoothing of the atmospheric term in SST algorithm


SST = aSST = a00 . BT . BT1111+ a+ a11. BT. BT1212 + a + a22.SST.SSTrefref.[(BT.[(BT1111-BT-BT1212))**HH](sec(Ɵ) -1)](sec(Ɵ) -1)

Low signal-to-stripe noise ratio (SSNR)Low signal-to-stripe noise ratio (SSNR)

Low-pass filterLow-pass filter

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Towards Operational Destriping Towards Operational Destriping

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RequirementsRequirements

Automatic:Automatic: Minimize supervision and algorithm tuning Minimize supervision and algorithm tuning

Robust:Robust: Maximize improvement of image quality, i.e., minimize: Maximize improvement of image quality, i.e., minimize: Residual stripesResidual stripes DistortionDistortion Processing artifactsProcessing artifacts

Fast:Fast: Suitable for real-time processing of satellite data. Suitable for real-time processing of satellite data.


Adaptive DestripingAdaptive Destriping

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Scene-based denoising algorithm based onScene-based denoising algorithm based on

Directional Hierarchical Decomposition (DHD) using on a Directional Hierarchical Decomposition (DHD) using on a unidirectional quadratic variational modelunidirectional quadratic variational model

Nonlocal filteringNonlocal filtering

““Adaptive Reduction of Striping for Improved SST Imagery from S-NPP VIIRS”, Adaptive Reduction of Striping for Improved SST Imagery from S-NPP VIIRS”, JTech, 2013 (in review)JTech, 2013 (in review)


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Directional Hierarchical DecompositionDirectional Hierarchical Decomposition


Observed image (f)Observed image (f)

Horizontal gradientHorizontal gradient Vertical gradientVertical gradient

11stst guess “True Image” (u guess “True Image” (u00)) 11stst guess noise (v guess noise (v00))

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== ++


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uu00 f-vf-v11

vv00 vv11 vv22 vv33 vv44 vv55 vv66

f, Noisy imagef, Noisy image

f-vf-v22 f-vf-v33 f-vf-v44 f-vf-v55 f-vf-v66

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Iteration #1Iteration #1 #2#2 #3#3 #4#4 #5#5 #6#6

Preliminary Results: DataPreliminary Results: Data

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Data: 3 days of level 1B/SDR TOA calibrated BTsData: 3 days of level 1B/SDR TOA calibrated BTs- Terra MODIS Terra MODIS - Aqua MODISAqua MODIS- NPP VIIRSNPP VIIRS

Destriping algorithm applied to SST bands @ 3.7, 11 and 12µmDestriping algorithm applied to SST bands @ 3.7, 11 and 12µm

Destriped BTs used as input in ACSPO prior to cloud masking and Destriped BTs used as input in ACSPO prior to cloud masking and SST productionSST production

Cloud mask and SST image quality compared with/without Cloud mask and SST image quality compared with/without destripingdestriping


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SST image quality (0.75 km) SST image quality (0.75 km)

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3/4/2013ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from original SDRs)


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3/4/2013ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from destriped SDRs)

SST Fronts (0.75 km)SST Fronts (0.75 km)

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ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from original SDRs)3/4/2013


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ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from destriped SDRs)3/4/2013


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SST image quality (4 km) SST image quality (4 km)

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SST image quality (4 km) SST image quality (4 km)

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SST Fronts (4 km)SST Fronts (4 km)

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SST Fronts (4 km)SST Fronts (4 km)

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Impact on cloud maskImpact on cloud mask

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Impact on cloud maskImpact on cloud mask

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Destriping performanceDestriping performance

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The Normalized Improvement Factor (NIF)The Normalized Improvement Factor (NIF)quantifies the improvement in image qualityquantifies the improvement in image quality


Monitoring of the NIF index over a 3 day period indicatesMonitoring of the NIF index over a 3 day period indicatesstable destriping performance (5% ≤ NIF stable destriping performance (5% ≤ NIF ≤ ≤ 30%)30%)

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ConclusionConclusion

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Stripe noise is clearly visible in MODIS and VIIRS level 2 SST and Stripe noise is clearly visible in MODIS and VIIRS level 2 SST and cloud maskcloud mask

It introduces relative errors of up to It introduces relative errors of up to 0.3 K0.3 K at the pixel level at the pixel level

.. and compromises downstream SST applications - .. and compromises downstream SST applications - classification/clustering, cloud mask, thermal fronts detection…classification/clustering, cloud mask, thermal fronts detection…

Downsampling SST from 1 km (or 0.75 km for VIIRS) to 2/4 km Downsampling SST from 1 km (or 0.75 km for VIIRS) to 2/4 km resolution does not really mitigate the problem…resolution does not really mitigate the problem…

On-orbit calibration/characterization can reduce striping but cannot On-orbit calibration/characterization can reduce striping but cannot remove it fully, due to numerous factors contributing to stripe noise remove it fully, due to numerous factors contributing to stripe noise

Scene-based post-processing to reduce stripe noise is the only Scene-based post-processing to reduce stripe noise is the only practical approach for improved SST imagerypractical approach for improved SST imagery

3/4/2013

Current status and future workCurrent status and future work

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CurrentlyCurrentlyRotational buffer of destriped VIIRS SST SDRs (M12, M15, M16)Rotational buffer of destriped VIIRS SST SDRs (M12, M15, M16)Rotational buffer of ACSPO VIIRS SST with destriped BTsRotational buffer of ACSPO VIIRS SST with destriped BTs

Future workFuture workEstimate SST coefficients from destriped BTsEstimate SST coefficients from destriped BTs

Generate ACSPO SST with new SST coefficientsGenerate ACSPO SST with new SST coefficientsEvaluate quantitative impact on SST retrieval. Evaluate quantitative impact on SST retrieval.


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Thank you!Questions?

323/4/2013 Destriping VIIRS/MODIS SST

MODIS and VIIRS SST bandsMODIS and VIIRS SST bands

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Terra /Aqua MODIS Terra /Aqua MODIS

Resolution at NadirResolution at Nadir 1 km1 kmFPA -> 10 DetectorsFPA -> 10 Detectors

S/MWIRS/MWIR λλ (µm) (µm) NE∆T (K)NE∆T (K)

Band 20 Band 20 3.7 3.7 0.050.05Band 22Band 22 3.9 3.9 0.070.07Band 23Band 23 4 4 0.070.07

LWIRLWIR λ λ (µm) (µm) NE∆T (K)NE∆T (K)

Band 31Band 31 11 11 0.05K0.05KBand 32Band 32 12 12 0.05K0.05K

Suomi NPP VIIRSSuomi NPP VIIRS

Resolution at NadirResolution at Nadir 0.75 km0.75 kmFPA -> 16 DetectorsFPA -> 16 Detectors

S/MWIR S/MWIR λλ (µm) (µm) NE∆T (K)NE∆T (K)

M12M12 3.7 3.7 0.40K0.40K

LWIRLWIR λλ (µm) (µm) NE∆T (K)NE∆T (K)

M15 11M15 11 0.07K0.07KM16 12M16 12 0.07K0.07K

Destriping VIIRS/MODIS SST

3/4/2013

Documents

Destriping of Viirs Modis Sst v2