application of in situ observations to current satellite-derived sea surface temperature products...
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Application of in situ Observations to Current Satellite-Derived Sea Surface Temperature Products
Gary A. Wick
NOAA Earth System Research Laboratory
With thanks to S. L. Castro, CCAR, University of Colorado, and D. L. Jackson, CIRES
Gary A. Wick NOAA Earth System Research Laboratory
Observed Differences BetweenInfrared and Microwave Products
Detailed comparisons between infrared and microwave SST products show complex spatial and temporal differences.
Gary A. Wick NOAA Earth System Research Laboratory
In Situ Observations
• Moored buoys– Better calibration– Ancillary data
• Drifting buoys– Poorer calibration– Best spatial sampling
• Ship-based subsurface measurements– Concerns with intake heating
• Ship-based radiometer measurements– Most directly related to satellite observations– Not available in sufficient numbers until recently
Gary A. Wick NOAA Earth System Research Laboratory
Historical Applications
• Operational SST algorithms and products– Algorithms derived from regression of satellite brightness
temperatures directly against in situ observations• Minimizes uncertainty related to atmospheric
transmission and surface processes• < 0.1 K Bias; ~0.5 K rms
– Independent set of buoys retained for validation
• Reynolds SST analysis– Optimal interpolation of satellite and in situ observations– In situ observations used to remove bias from satellite data
Gary A. Wick NOAA Earth System Research Laboratory
Ongoing Activities
• GODAE High Resolution Sea Surface Temperature Pilot Project
• National Ocean Partnership Program– Partnered with NESDIS, NRL, Universities,
Remote Sensing Systems
www.ghrsst-pp.org
www.misst.org
Gary A. Wick NOAA Earth System Research Laboratory
Error Characterization Approach
• Construct collocations between buoy measurements and satellite retrievals
• Bin satellite – in situ SST differences as functions of multiple environmental parameters
• Identify dominant dependencies• Express bias and rms estimates through
multi-dimensional look-up tables• Parameter combinations evaluated through
reduction in sensor-buoy and sensor-sensor differences
Gary A. Wick NOAA Earth System Research Laboratory
Data Sources
• Infrared Satellite Data– AVHRR
• Operational NLSST - Naval Oceanographic Office
• Microwave Satellite Data– AMSR-E– TRMM Microwave Imager (TMI)
• Remote Sensing Systems – Wentz and Gentemann
• Buoys– QC’d GTS buoys via NCEP/CDC
Gary A. Wick NOAA Earth System Research Laboratory
AVHRR Uncertainty Sources
Gary A. Wick NOAA Earth System Research Laboratory
AVHRR Uncertainty Sources
Gary A. Wick NOAA Earth System Research Laboratory
Microwave Uncertainty Sources
Gary A. Wick NOAA Earth System Research Laboratory
Microwave Uncertainty Sources
Gary A. Wick NOAA Earth System Research Laboratory
Sample Bias Adjustments
Gary A. Wick NOAA Earth System Research Laboratory
Formulation Evaluation
• Applied derived bias adjustments to satellite observations
• Computed change in standard deviation of the satellite – buoy differences
• Done for both dependent (reanalysis) and independent (operational) periods
• Evaluates bias only
Gary A. Wick NOAA Earth System Research Laboratory
Evaluation of Bias Adjustments
Terms Net STD Reduction (%)
STD Reduction for Points
Adjusted (%)
Points Adjusted (%)
WS, WV, SST 5.79 5.85 99.7
WS, SST 2.75 2.75 100.0
WS, WV, SST, Ts-Ta 2.65 3.14 87.4
WS, Ts-Ta, SST 3.81 4.33 89.1
AMSR-E Independent Validation, Oct-Dec, 2003
Gary A. Wick NOAA Earth System Research Laboratory
Impact of the Bias Adjustments
Before Adjustment
After Adjustment
http://www.ghrsst-pp.org
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Ingestion, Dissemination andProcessing Service (IDPS)
Global Data Analysis Centre (GDAC)
SST data products (L2P, L4)
Regional Data Assembly Centres (RDAC)
RDAC RDAC RDAC RDAC RDAC
HR-DDSarchive
ProductRollingArchive
Metadatarepository
(MMR)
Matchupdatabase
(MDB)USA EU
Global coverage L4 SST products
Global L4 analysis systems…
GHRSST-PP Long Term Stewardship
and Reanalysis Facility (LTSRF) at NODC
Historical time series SST CDR products
GHRSST Regional/Global Task Sharing
A working demonstration of GEOSS!
Gary A. Wick NOAA Earth System Research Laboratory
GHRSST Use of In Situ Data
• Buoy observations adopted as source of accuracy estimates for all satellite sensors
• Real-time matchup database maintained for all sensors
• Bias and rms estimates updated weekly based on database
• Efforts to withhold in situ observations from analyses to retain independence
Gary A. Wick NOAA Earth System Research Laboratory
Prototype Radiometric Skin Observing System
• NOPP project to demonstrate the feasibility and assess the impact of routine radiometric observations of the skin temperature
• Multiple radiometers on ships-of-opportunity over a 3-year period– M-AERI on Royal Caribbean Explorer of the Seas– CIRIMS on Research Vessels Ron Brown and Thompson– ISAR on ferry and merchant vessel
P. Minnett A. Jessup
W. Wimmer
Gary A. Wick NOAA Earth System Research Laboratory
Impact on Satellite Algorithms
• Derived simultaneous skin and subsurface SST regression algorithms from coincident observations
• Evaluated accuracy with independent observations• Accuracy generally better for subsurface SST
retrievals– Likely related to greater variability of skin observations
• Final results still being analyzed
CIRIMS matchups
2003-4
M-AERI matchups
2004
Gary A. Wick NOAA Earth System Research Laboratory
Ongoing Issues
• Independent observations• Sufficient accuracy• Adequate sampling of all representative
environmental conditions
Gary A. Wick NOAA Earth System Research Laboratory
Optimal Characterization
• Infrared– Satellite zenith angle– Channel 4-5 brightness temperature
difference– Sea surface temperature– Climatological anomaly
• Microwave– Wind speed– Water vapor content– SST– Climatological anomaly