Drifter SST Study. Inset: VOS crew deploy next generation SVP Drifter

Drifter SST Study. Inset: VOS crew deploy an SVP Drifter


Drifting buoy SST observations are essential to validate satellite SST retrievals because FRM Thermal Infrared radiometers are not yet available in sufficient numbers. The much larger number of drifter SST matchups (typically 1300 active globally at any time) compared to other in situ sources allows the inherent resolution and accuracy limitations of historical drifter SST to statistically overcome these limitations.

Drifting buoy SST was never designed as an FRM for satellite SST validation, although it could easily have been had the requirement been known. The Group for High Resolution SST (GHRSST) has fostered the development of new global SST data products based on the complementary characteristics of diverse types of SST observing systems which include uncertainty estimates derived largely from the global drifting buoy array. In collaboration with GHRSST, the IOC/WMO Data Buoy Co-operation Panel (DBCP) has also been active in piloting the deployment of a new generation of HRSST drifters that are expected to better serve the requirements of the satellite SST community. The HRSST concept is to be further tested through a pilot study being commissioned by EUMETSAT that will see significant numbers of HRSST drifters deployed in areas where good matchups with the recently launched Sentinel-3 SLSTR might be expected.

The adequacy of the in situ network for the correction of satellite SST biases depends on the choice of error model. Little work has been performed to establish SI traceability to drifting buoy measurements of SST with National Metrology Institutes. Some activities have used AATSR (Advanced Along Track Scanning Radiometer) satellite data to understand the characteristics of errors in ship SST, moored and drifting buoys.

An approach to establish the best route to SI traceability for SST sensors on drifting buoys and other in-water devices that are used to validate satellite SST measurements but are not typically retrieved for post deployment calibration verification is required.

Work in the FRM4STS project

The planned drifter SST work in the FRM4STS project is to:

(a) Contribute to a technical report “Towards SI traceability for non-recoverable SST and IST FRM instruments”, including:

  1. A review of current SST measurements highlighting calibration issues.
  2. An assessment of different options to establish a route to SI traceability for non-recoverable SST instruments.
  3. Define a justified approach and methodology to establish the best route to traceability for non-recoverable SST instruments.
  4. Establish protocols to implement the approach and methodology selected.
  5. Establish example uncertainty budgets (determined in agreement with defined National Standards Laboratory protocols) for non-recoverable SST instruments.
  6. As a worked example, assess the performance of DBCP HRSST drifting buoys developed for satellite SST validation in collaboration with GHRSST using the defined protocols and approach,
  7. Develop a roadmap for future evolution of the approach.

(b) Organise a Scientific and Technical meeting “Towards SI Traceability for non-recoverable SST and IST FRM Instruments” to present discuss the results of this task together with the external community.

Scientific and technical workshop on traceability of drifter SST measurements

The SST-Drift workshops review progress made on traceability of drifter SST measurements and look to reach a consensus on the way forward for drifter SST measurements and the establishment of best practice for the community.

You can find copies of the presentations within each of the held workshop agendas here:

A poster; Towards Improved Drifter SST: A Collaboration between the Satellite Community and the Data Buoy Co-Operation Panel by David Meldrum, Jon Turton, Gary Corlett, Craig Donlon and Anne O’Carroll is now available to download.

Prof David Meldrum, FInstP
Honorary Research Fellow, Technology Development
Scottish Marine Institute
Oban PA37 1QA
Scotland – UK
T: (+44) 1866 822158
M: (+44) 7774 690630