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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
VIIRS Maps and Histograms
Hovmöller Diagrams
Background

• 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
AVHRRAMSR-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
ESA CCI ARC (ongoing)
NESDIS ACSPO
EUMETSAT OSI 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
  ?TSTS-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 ?TS are expected to be close to zero and
  globally uniform
• PDFs of ?TS are near-Gaussian (although TS and TR
  are skewed)
• In addition to ?TS 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// doi10.1175/2010JTEC
  HA1413.1)
• Xu and Ignatov, 2010. Evaluation of in situ
  SSTs, JGR-Oceans (doi10.1029/2010JC006129)

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 QCed 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, MD Contact
Prasanjit.Dash_at_noaa.gov Phone [phone]
AVHRR SST OSTIA