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

16

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