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Destriping of VIIRS and MODIS SST imagery Marouan Bouali and Alexander Ignatov NOAA/NESDIS/STAR and CSU/CIRA 1 Workshop: “SST from polar orbiters: use.

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Presentation on theme: "Destriping of VIIRS and MODIS SST imagery Marouan Bouali and Alexander Ignatov NOAA/NESDIS/STAR and CSU/CIRA 1 Workshop: “SST from polar orbiters: use."— Presentation transcript:

1 Destriping of VIIRS and MODIS SST imagery Marouan Bouali and Alexander Ignatov NOAA/NESDIS/STAR and CSU/CIRA 1 Workshop: “SST from polar orbiters: use of NWP models” Centre de Météorologie Spatiale, Météo France, Lannion March 5-7, /4/2013Destriping VIIRS/MODIS SST

2 Motivation Native resolution SST imagery (≤1km) derived from whiskbroom scanners (MODIS, VIIRS) is affected with stripe noise 2 Sea Surface Temperatures (°C) Destriping VIIRS/MODIS SST Terra MODIS Aqua MODIS NPP VIIRS 3/4/2013 T L2_LAC_SSTA L2_LAC_SSTACSPO_V2.12_NPP_VIIRS_ _

3 Accuracy of SST retrieval 3 NPP VIIRS (0.75 km) Stripe noise in level 1B or SDRs BTs can lead to SST errors of up to ± 0.3K Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _

4 SST Fronts 4 NPP VIIRS (0.75 km) Sobel filter Striping introduces artificial structures and affects the analysis of thermal fronts (orientation, intensity and location) Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _

5 5 Prior to assimilating into UHR L4 SST, MODIS and VIIRS L2 SSTs should be destriped Destriping VIIRS/MODIS SST UHR L4 SST will be increasingly used as input in NWP models due to better weather prediction (LaCasse et al. 2008) ESA MEDSPIRATION NASA JPL MUR NASA JPL G1SST Ultra-High Resolution Level 4 SSTs 3/4/2013

6 Mitigation of striping 6  Currently, blackbody (BB) and space view (SV) are used for absolute BT calibration on a scan-by-scan basis  This practice ensures that sensor uniformity performance is within pre-launch specification BUT it does not guarantee full mitigation of striping effect  Post-processing of L1B (SDR) is required to generate improved L1B, from which SST products with improved image quality can be produced Destriping VIIRS/MODIS SST 3/4/2013

7 Destriping Literature 7  ~ 40 years of research (since Landsat MSS, 1972)  Techniques with potential for operational use are intended for highly pronounced stripe noise whereas,  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 imagery other than…  Spatial smoothing of the atmospheric term in SST algorithm Destriping VIIRS/MODIS SST SST = a 0. BT 11 + a 1. BT 12 + a 2.SST ref.[(BT 11 -BT 12 ) * H](sec( Ɵ ) -1) Low signal-to-stripe noise ratio (SSNR) Low-pass filter 3/4/2013

8 Towards Operational Destriping 8 Requirements Automatic: Minimize supervision and algorithm tuning Robust: Maximize improvement of image quality, i.e., minimize:  Residual stripes  Distortion  Processing artifacts Fast: Suitable for real-time processing of satellite data. Destriping VIIRS/MODIS SST

9 Adaptive Destriping 9 Scene-based denoising algorithm based on  Directional Hierarchical Decomposition (DHD) using on a unidirectional quadratic variational model  Nonlocal filtering “Adaptive Reduction of Striping for Improved SST Imagery from S-NPP VIIRS”, JTech, 2013 (in review) Destriping VIIRS/MODIS SST 3/4/2013

10 Adaptive Destriping 10 Directional Hierarchical Decomposition Destriping VIIRS/MODIS SST Observed image (f) Horizontal gradient Vertical gradient 1 st guess “True Image” (u 0 ) 1 st guess noise (v 0 ) 3/4/2013 = +

11 Adaptive Destriping 11 Destriping VIIRS/MODIS SST u0u0u0u0 f-v 1 v0v0v0v0 v1v1v1v1 v2v2v2v2 v3v3v3v3 v4v4v4v4 v5v5v5v5 v6v6v6v6 f, Noisy image f-v 2 f-v 3 f-v 4 f-v 5 f-v 6 3/4/2013 Iteration #1 #2#3#4#5#6

12 Preliminary Results: Data 12  Data: 3 days of level 1B/SDR TOA calibrated BTs -Terra MODIS -Aqua MODIS -NPP VIIRS  Destriping algorithm applied to SST 3.7, 11 and 12µm  Destriped BTs used as input in ACSPO prior to cloud masking and SST production  Cloud mask and SST image quality compared with/without destriping Destriping VIIRS/MODIS SST 3/4/2013

13 SST image quality (0.75 km) 13 Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _ (from original SDRs)

14 SST image quality (0.75 km) 14 Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _ (from destriped SDRs)

15 SST Fronts (0.75 km) 15 Destriping VIIRS/MODIS SST ACSPO_V2.12_NPP_VIIRS_ _ (from original SDRs) 3/4/2013

16 SST Fronts (0.75 km) 16 Destriping VIIRS/MODIS SST ACSPO_V2.12_NPP_VIIRS_ _ (from destriped SDRs) 3/4/2013

17 SST image quality (0.75 km) 17 Destriping VIIRS/MODIS SST ACSPO_V2.12_NPP_VIIRS_ _ (from original SDRs) 3/4/2013

18 SST image quality (0.75 km) 18 Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _ (from destriped SDRs)

19 SST Fronts (0.75 km) 19 Destriping VIIRS/MODIS SST ACSPO_V2.12_NPP_VIIRS_ _ (from original SDRs) 3/4/2013

20 SST Fronts (0.75 km) 20 Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _ (from destriped SDRs)

21 SST image quality (0.75 km) 21 Destriping VIIRS/MODIS SST ACSPO_V2.12_NPP_VIIRS_ _ (from original SDRs) 3/4/2013

22 SST image quality (0.75 km) 22 Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _ (from destriped SDRs)

23 SST image quality (4 km) 23 Destriping VIIRS/MODIS SST ACSPO_V2.12_NPP_VIIRS_ _ (from original SDRs) 3/4/2013

24 SST image quality (4 km) 24 Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _ (from destriped SDRs)

25 SST Fronts (4 km) 25 Destriping VIIRS/MODIS SST ACSPO_V2.12_NPP_VIIRS_ _ (from original SDRs) 3/4/2013

26 SST Fronts (4 km) 26 Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _ (from destriped SDRs)

27 Impact on cloud mask 27 Destriping VIIRS/MODIS SST ACSPO_V2.12_NPP_VIIRS_ _ (from original SDRs) 3/4/2013

28 Impact on cloud mask 28 Destriping VIIRS/MODIS SST 3/4/2013 ACSPO_V2.12_NPP_VIIRS_ _ (from destriped SDRs)

29 Destriping performance 29 The Normalized Improvement Factor (NIF) quantifies the improvement in image quality Destriping VIIRS/MODIS SST Monitoring of the NIF index over a 3 day period indicates stable destriping performance (5% ≤ NIF ≤ 30%) 3/4/2013

30 Conclusion 30 Destriping VIIRS/MODIS SST  Stripe noise is clearly visible in MODIS and VIIRS level 2 SST and cloud mask  It introduces relative errors of up to 0.3 K at the pixel level .. and compromises downstream SST applications - classification/clustering, cloud mask, thermal fronts detection…  Downsampling SST from 1 km (or 0.75 km for VIIRS) to 2/4 km resolution does not really mitigate the problem…  On-orbit calibration/characterization can reduce striping but cannot remove it fully, due to numerous factors contributing to stripe noise  Scene-based post-processing to reduce stripe noise is the only practical approach for improved SST imagery 3/4/2013

31 Current status and future work 31 Currently Rotational buffer of destriped VIIRS SST SDRs (M12, M15, M16) Rotational buffer of ACSPO VIIRS SST with destriped BTs Future work Estimate SST coefficients from destriped BTs Generate ACSPO SST with new SST coefficients Evaluate quantitative impact on SST retrieval. Destriping VIIRS/MODIS SST 3/4/2013

32 Thank you! Questions? 323/4/2013Destriping VIIRS/MODIS SST

33 MODIS and VIIRS SST bands 33 Terra /Aqua MODIS Resolution at Nadir1 km FPA -> 10 Detectors S/MWIR λ (µm) NE∆T (K) Band Band Band LWIR λ (µm) NE∆T (K) Band K Band K Suomi NPP VIIRS Resolution at Nadir0.75 km FPA -> 16 Detectors S/MWIR λ (µm) NE∆T (K) M K LWIR λ (µm) NE∆T (K) M K M K Destriping VIIRS/MODIS SST 3/4/2013


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