VIIRS radiances and imagery have reached a stable and accurate performance for SST retrieval.

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First year of VIIRS SST in SQUAM: Evaluation and comparison with other satellite SSTs Prasanjit Dash1,2, Sasha Ignatov1, Yury Kihai1,3, John Stroup1,4, Xingming Liang1,2, John Sapper1, Feng Xu1,3 1NOAA/NESDIS ; 2Colorado State University-CIRA; 3GST Inc; 4STG Inc Background VIIRS Maps and Histograms Hovmöller Diagrams • S-NPP was launched in Oct-2011: Bridge mission between NOAA-POES/NASA-EOS & the future Joint Polar Satellite System (JPSS). • VIIRS: builds upon MODIS heritage & supersedes AVHRR operations. • Global VIIRS SST products: IDPS (JPSS) & ACSPO (NOAA heritage) • ACSPO also used to derive SST from several AVHRRs (onboard NOAA-16, 18-19, Metop-A & B), and two MODISs onboard Terra/Aqua • SST Quality Monitor (www.star.nesdis.noaa.gov/sod/sst/squam/; SQUAM) is a web-based near real-time (NRT) tool to monitor global community SST products for stability and cross-platform consistency Day, VIIRS – OSTIA, mean Night, VIIRS – OSTIA, mean a) VIIRS (ACSPO) day SST minus OSTIA, 31-Mar-2013 ACSPO: b) VIIRS (IDPS) day SST minus OSTIA, 31-Mar-2013 L2- and L3- SQUAM: (L2 – L4) • L4-SQUAM: (L4 – L4) • Reynolds (AVHRR; AVHRR+AMSR-E*) • RTG (high, low) • NAVO K10 • POES GOES Blended • NASA JPL: 1km G1SST, 1km MUR • OSTIA (real-time, reanalyzed) • CMC0.2° (real-time; reanalyzed ongoing) • GAMSSA, ODYSSEA • GMPE • *AMSR-E discontinued in 2011 • +pending inclusion of RSS, NCODA Cloud Mask and SST Algorithm issues are seen in ACSPO and to a greater extent in IDPS Bulk L2 (LEO) L3 (LEO) High Res (HR) (AVHHR/MODIS/VIIRS) IDPS: PathFinder v5.0 PathFinder v6.0 (future) (A)ATSR [ESACCI ARC] (ongoing) NESDIS ACSPO EUMETSAT O&SI SAF JPSS IDPS Foundation GAC (Global Area Coverage) NESDIS Heritage MUT Newer ACSPO NAVO SEATEMP Ensemble Fig. 1: L2-SQUAM diagnostics for NPP VIIRS SST w.r.t. OSTIA. IDPS sample is ~24% larger than ACSPO, but performance statistics degraded. Fig. 3: Mean of “VIIRS- OSTIA” in Hovmöller space. Working to improve the performance of IDPS SST and bring it closer to NOAA heritage ACSPO. Table 1: Sea surface temperature (SST) products monitored in SQUAM Time-series: Stability of SSTs Summary and Outlook L2/L3 SQUAM Concept Reference = OSTIA Reference = Drifters Night • VIIRS radiances and imagery have reached a stable and accurate performance for SST retrieval. • VIIRS SST EDR was declared “beta” in Feb 2013. Data will be openly available via CLASS in near-future. • SQUAM routinely monitors VIIRS SSTs from IDPS and ACSPO, as well as other community SST products from AVHRRs and MODISs. • IDPS SST product shows cloud and ice leakages and inferior performance compared to ACSPO. • SST monitoring is done in difference space: ΔTS=TS-TR. • Customarily, satellite (L2, L3) and analysis (L4) SSTs products are validated against in situ SSTs (TR = Tin situ) • However, in situ data are sparse, geographically biased, of non-uniform and often suboptimal quality, and not available in NRT. • Therefore in SQUAM, gap-free L4 fields are additionally employed. • They cover the full global ocean, have more uniform quality, and are available in NRT. • Monitoring against L4s allows quick snapshots and global diagnostics of L2 SST, daily • Maps of ΔTS are expected to be close to zero and globally uniform • PDFs of ΔTS are near-Gaussian (although TS and TR are skewed) • In addition to ΔTS maps and histograms, time series, dependencies, and Hovmöller plots ar also produced in SQUAM. Ice-mask issue in IDPS: uncovered with SQUAM Future Work Warm-up / cool-down event Day • Improve ACSPO and IDPS products. • Continue monitoring in SQUAM. Improve presentation (e.g., include bivariate density plots, monthly validation in addition to currently daily). References VIIRS SST monitoring Ice-mask issue in IDPS: uncovered with SQUAM • Dash et al., 2012. GHRSST Analysis Fields Inter-Comparisons: Part 2, DSR-II (dx.doi.org/10.1016/j.dsr2.2012.04.002) • Dash et al., 2010. : The SST Quality Monitor (SQUAM). JTech-Oceans. (http://dx.doi.org/10.1175/2010JTECHO756.1) • Petrenko et al., 2010. Clear-sky mask for the ACSPO. JTech-Oceans. (http:// doi:10.1175/2010JTECHA1413.1) • Xu and Ignatov, 2010. Evaluation of in situ SSTs…, JGR-Oceans (doi:10.1029/2010JC006129) Warm-up / cool-down event • Fig 1 shows example diagnostics of VIIRS SST (ACSPO & IDPS) against OSTIA L4 SST. • Other Reference SSTs available in SQUAM include Reynolds, OSTIA, RTG, iQuam QC’ed in situ Acknowledgements & Disclaimer Fig. 2: Mean and Std Dev w.r.t. OSTIA (left) and Drifters (right). IDPS SST consistently shows degraded performance compared to ACSPO. Work is underway to improve IDPS performance. This work was supported by JPSS and GOES-R Program Offices, and NOAA PSDI, NDE and ORS Programs. We thank our NOAA, OSI SAF, U. Miami, and NAVO SST colleagues and wider GHRSST community for making products available, and helpful discussions. The views and findings are those of the authors and should not be construed as an official NOAA or US Government position, policy, or decision. 2013 NOAA Satellite Conference, April 8-12 2013, NOAA Center for Weather and Climate Prediction (NCWCP), College Park, MDContact: Prasanjit.Dash@noaa.gov Phone: 301-683- 3363 AVHRR SST– OSTIA