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Destriping of VIIRS and MODIS SST imagery

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

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Destriping of VIIRS and MODIS SST imagery

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

  2. Motivation Native resolution SST imagery (≤1km) derived from whiskbroom scanners (MODIS, VIIRS) is affected with stripe noise Terra MODIS Aqua MODIS NPP VIIRS T2012294110000.L2_LAC_SST A2012294031500.L2_LAC_SST ACSPO_V2.12_NPP_VIIRS_2012-10-20_1510-1519 Sea Surface Temperatures (°C) Destriping VIIRS/MODIS SST

  3. Accuracy of SST retrieval Stripe noise in level 1B or SDRs BTs can lead to SST errors of up to ± 0.3K NPP VIIRS (0.75 km) ACSPO_V2.12_NPP_VIIRS_2012-10-20_1510-1519 Destriping VIIRS/MODIS SST

  4. SST Fronts NPP VIIRS (0.75 km) Striping introduces artificial structures and affects the analysis of thermal fronts (orientation, intensity and location) Sobel filter ACSPO_V2.12_NPP_VIIRS_2012-10-20_1840-1849 Destriping VIIRS/MODIS SST

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

  6. Mitigation of striping • 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

  7. Destriping Literature • ~ 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 Low-pass filter SST = a0 . BT11+ a1. BT12 + a2.SSTref.[(BT11-BT12)*H](sec(Ɵ) -1) Low signal-to-stripe noise ratio (SSNR) Destriping VIIRS/MODIS SST

  8. Towards Operational Destriping 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 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

  10. Adaptive Destriping Directional Hierarchical Decomposition Horizontal gradient Vertical gradient 1st guess noise (v0) Observed image (f) 1st guess “True Image” (u0) = + Destriping VIIRS/MODIS SST

  11. Adaptive Destriping f, Noisy image #2 #3 #4 #5 #6 Iteration #1 u0 f-v1 f-v2 f-v3 f-v4 f-v5 f-v6 v0 v1 v2 v3 v4 v5 v6 Destriping VIIRS/MODIS SST

  12. Preliminary Results: Data • Data: 3 days of level 1B/SDR TOA calibrated BTs • Terra MODIS • Aqua MODIS • NPP VIIRS • Destriping algorithm applied to SST bands @ 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

  13. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from original SDRs) Destriping VIIRS/MODIS SST

  14. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from destriped SDRs) Destriping VIIRS/MODIS SST

  15. SST Fronts (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from original SDRs) Destriping VIIRS/MODIS SST

  16. SST Fronts (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from destriped SDRs) Destriping VIIRS/MODIS SST

  17. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-24_0300-0309 (from original SDRs) Destriping VIIRS/MODIS SST

  18. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-24_0300-0309 (from destriped SDRs) Destriping VIIRS/MODIS SST

  19. SST Fronts (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-24_0300-0309 (from original SDRs) Destriping VIIRS/MODIS SST

  20. SST Fronts (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-24_0300-0309 (from destriped SDRs) Destriping VIIRS/MODIS SST

  21. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from original SDRs) Destriping VIIRS/MODIS SST

  22. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from destriped SDRs) Destriping VIIRS/MODIS SST

  23. SST image quality (4 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from original SDRs) Destriping VIIRS/MODIS SST

  24. SST image quality (4 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from destriped SDRs) Destriping VIIRS/MODIS SST

  25. SST Fronts (4 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from original SDRs) Destriping VIIRS/MODIS SST

  26. SST Fronts (4 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from destriped SDRs) Destriping VIIRS/MODIS SST

  27. Impact on cloud mask ACSPO_V2.12_NPP_VIIRS_2013-01-31_0600-0609 (from original SDRs) Destriping VIIRS/MODIS SST

  28. Impact on cloud mask ACSPO_V2.12_NPP_VIIRS_2013-01-31_0600-0609 (from destriped SDRs) Destriping VIIRS/MODIS SST

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

  30. Conclusion • 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 Destriping VIIRS/MODIS SST

  31. Current status and future work 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

  32. Thank you!Questions? Destriping VIIRS/MODIS SST

  33. MODIS and VIIRS SST bands Terra /Aqua MODIS Resolution at Nadir 1 km FPA -> 10 Detectors S/MWIRλ (µm)NE∆T (K) Band 20 3.7 0.05 Band 22 3.9 0.07 Band 23 4 0.07 LWIR λ (µm)NE∆T (K) Band 31 11 0.05K Band 32 12 0.05K Suomi NPP VIIRS Resolution at Nadir 0.75 km FPA -> 16 Detectors S/MWIR λ (µm) NE∆T (K) M12 3.7 0.40K LWIRλ (µm) NE∆T (K) M15 11 0.07K M16 12 0.07K Destriping VIIRS/MODIS SST

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