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Reduction of stripe noise in ACSPO clear-sky radiances and SST

Reduction of stripe noise in ACSPO clear-sky radiances and SST. Marouan Bouali and Alexander Ignatov NOAA/NESDIS/STAR and CSU/CIRA. SPIE Security, Defense and Sensing 2013, Baltimore, MD. Motivation.

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Reduction of stripe noise in ACSPO clear-sky radiances and SST

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  1. Reduction of stripe noise in ACSPO clear-sky radiances and SST Marouan Bouali and Alexander Ignatov NOAA/NESDIS/STAR and CSU/CIRA SPIE Security, Defense and Sensing 2013, Baltimore, MD

  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) SPIE Security, Defense and Sensing, Baltimore, MD

  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 SPIE Security, Defense and Sensing, Baltimore, MD

  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 SPIE Security, Defense and Sensing, Baltimore, MD

  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) SPIE Security, Defense and Sensing, Baltimore, MD

  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 SPIE Security, Defense and Sensing, Baltimore, MD

  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) SPIE Security, Defense and Sensing, Baltimore, MD

  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. SPIE Security, Defense and Sensing, Baltimore, MD

  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) SPIE Security, Defense and Sensing, Baltimore, MD

  10. Adaptive Destriping Directional Hierarchical Decomposition Horizontal gradient Vertical gradient 1st guess noise (v0) Observed image (f) 1st guess “True Image” (u0) = + SPIE Security, Defense and Sensing, Baltimore, MD

  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 SPIE Security, Defense and Sensing, Baltimore, MD

  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 SPIE Security, Defense and Sensing, Baltimore, MD

  13. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from original SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  14. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from destriped SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  15. SST Fronts (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from original SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  16. SST Fronts (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-27_1910-1919 (from destriped SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  17. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-24_0300-0309 (from original SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  18. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-24_0300-0309 (from destriped SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  19. SST Fronts (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-24_0300-0309 (from original SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  20. SST Fronts (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-24_0300-0309 (from destriped SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  21. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from original SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  22. SST image quality (0.75 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from destriped SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  23. SST image quality (4 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from original SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  24. SST image quality (4 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from destriped SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  25. SST Fronts (4 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from original SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  26. SST Fronts (4 km) ACSPO_V2.12_NPP_VIIRS_2013-01-21_0740-0749 (from destriped SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  27. Impact on cloud mask ACSPO_V2.12_NPP_VIIRS_2013-01-31_0600-0609 (from original SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  28. Impact on cloud mask ACSPO_V2.12_NPP_VIIRS_2013-01-31_0600-0609 (from destriped SDRs) SPIE Security, Defense and Sensing, Baltimore, MD

  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%) SPIE Security, Defense and Sensing, Baltimore, MD

  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 SPIE Security, Defense and Sensing, Baltimore, MD

  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?

  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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