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SST from Suomi -NPP VIIRS: Algorithm Development And Uncertainty Estimation

SST from Suomi -NPP VIIRS: Algorithm Development And Uncertainty Estimation Peter J Minnett, Robert H Evans, Kay Kilpatrick, Guillermo Podestá , Elizabeth Williams , Goshka Szczodrak , Miguel Izaguirre , Sue Walsh & Michael Reynolds*

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SST from Suomi -NPP VIIRS: Algorithm Development And Uncertainty Estimation

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  1. SST from Suomi-NPP VIIRS: Algorithm Development And Uncertainty Estimation Peter J Minnett, Robert H Evans, Kay Kilpatrick, Guillermo Podestá, Elizabeth Williams, GoshkaSzczodrak, Miguel Izaguirre, Sue Walsh & Michael Reynolds* Rosenstiel School of Marine and Atmospheric Science, University of Miami *Remote Measurements and Research Co., Seattle

  2. Outline Overview of VIIRS characteristics relevant for SST retrievals. Form of the atmospheric correction algorithms. Uncertainties: • comparisons vs drifting buoys. • comparisons vs ship radiometers. Future directions.

  3. Search for new S-NPP logo…. ?? S-NPP

  4. Introduction VIIRS is the first of a new class of satellite radiometer, using design elements from MODIS and SeaWiFS. At least two more VIIRS will be flown on the NOAA JPSS satellites replacing the AVHRRs on the NOAA-n polar orbiters. The European radiometer to replace the AVHRRs on MetOp-A and MetOp-B, called METimage, will have a similar optical design, but will have SST channels more similar to MODIS.

  5. Suomi NPP • Launched on 28 October, 2011. • Equator crossing - 1:30 p.m. • Altitude of 824 km. • 16-day repeat cycle • Five key instruments: • Advanced Technology Microwave Sounder (ATMS) • Cross-track Infrared Sounder (CrIS) • Ozone Mapping and Profiler Suite (OMPS) • Clouds and the Earth's Radiant Energy System (CERES) • Visible Infrared Imaging Radiometer Suite (VIIRS) Photo courtesy Ball Aerospace.

  6. VIIRS • Rotating telescope with “Half-Angle Mirror” fore-optics. • Spectral Bands: – Visible/ Near IR: 9 plus Day/Night Band – Mid-Wave IR: 8 – Long-Wave IR: 4 • Imaging Optics: 18.4 cm Aperture. • 114 cm Focal Length. • Scan Range of earth view: ±56º from nadir. • Swath width: 3000 km.

  7. VIIRS Components

  8. VIIRS spectral bands

  9. VIIRS SST RSRs

  10. VIIRS pixel aggregation GSD: Ground Sampling Distance HSI: Horizontal Sampling Interval

  11. VIIRS vs MODIS spatial resolution From http://www.ipo.noaa.gov/ams/2010/posters/AGU_AMS-RAY_NGAS-VIIRSHeritageSystems-SNODGRASS_GUENTHER_ANDREAS-WE_PRINT-PR.pdf

  12. Miami decision-tree cloud mask

  13. VIIRS Atmospheric Correction Algorithms Miami V6: • SST2b = a0 + a1T11 + a2(T11 – T12) Tsfc + a3(T11-T12)Sq • SST3b = a0 + a1T11 + a2(T3.7 – T12) Tsfc + a3Sq Miami V7: • SST2b = a0 + a1T11+ a2(T11– T12) Tsfc+ a3(T11-T12)Sq+ a4Sq+ a5Sqχ χ = fn(lat) • SST3b = a0 + a1T11+ a2(T3.7– T12) Tsfc+ a3Sq+ a4Sqχ χ = 0.1 for |lat| ≤ 40°; 2.0 for |lat| > 40° Sq= sec(θ)-1

  14. Spatial distribution of errors Comparisons with buoys

  15. Simple Global Statistics

  16. SST 2b - night OSI-SAF IDPS IDPS latband Miami V7 OSI-SAF IDPS IDPS latband Miami V7

  17. SST 3b - night OSI-SAF IDPS IDPS latband Miami V7 OSI-SAF IDPS IDPS latband Miami V7

  18. Spatial comparisons – AVHRR OI

  19. Spatial comparisons – WindSat

  20. Time dependences SST 2b day SST 2b night SST 3b night Comparisons with buoys

  21. Ship radiometers: M-AERIs M-AERIs, new and old, on R/V Knorr. Transit from Woods Hole to Cape Town, and an Agulhas mooring recovery cruise. Mean 0.024K, stdev = 0.201K, n = 78 VIIRS v7.0 algorithm Reference SST WindSat 5day average. Skin SST measurements from R/V Knorr. January – March 2013. M-AERIs are Fourier Transform Infrared interferometers with two internal blackbody calibration targets. Pre- & post-deployment lab calibration against NIST-traceable calibrators.

  22. Ship radiometers: ISARs M/V Andromeda Leader M/V Horizon Spirit Mean -0.058 K, stdev = 0.417K, n = 337 ISARs are autonomous filter radiometers with two internal blackbody calibration targets. Pre- & post-deployment lab calibration against NIST-traceable calibrators. Data relayed in real-time by Iridium.

  23. Spatial distribution of errors Comparisons with ship radiometers

  24. Summary • VIIRS is a good SST radiometer, as good as, if not better than MODIS. • Errors are fairly stable in time. • Spatial comparisons with WindSat microwave SSTs give more uniform agreement than with infrared OI SSTs. • Full swath retrievals are improved by the use of additional zenith angle terms. • Form of algorithms provides continuity with heritage sensors. • Comparison with ship-board radiometers provides mechanism for contributing the SST Climate Data Record.

  25. Future directions • Continue to populate matchup data base, leading to error hypercube. • Continue refinement of atmospheric correction algorithm. • Compare with AMSR2 microwave SSTs. • Continue matchups with ship radiometers – provide pathway to contributing to the SST CDR. • Work with NASA Goddard Ocean Color Processing Group and with NASA JPL PO.DAAC to produce VIIRS SSTs in GHRSST L2P format for wider distribution to the community. • Continue to work with NOAA STAR VIIRS Team.

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