NPL to provide global traceability for Earth surface Temperature measurements

The Earth Observation, Climate and Optical (ECO) group has won a €500k contract with ESA to intercompare instruments used to measure the Earth’s surface temperature (Ocean, Land and Ice) to validate satellite observations.

Measurement of change in the temperature of the Earth’s surface is crucial to our understanding of climate. Sea Surface Temperature, for example, is one of the Essential Climate variables (ECV) and one where we are seeking to detect changes as small as a 0.2 °C per decade. The global nature of such measurements means they are highly reliant on satellite observations with a key sensor from ESA (Sea and Land Surface Temperature Radiometer (SLSTR) planned to be launch as part of the Sentinel 3 mission later this year. NPL is also providing traceability to this sensor through other projects.

The project called ‘Fiducial Reference Measurements for Surface Temperature validation of Satellites’ (FRM4STS) has at its core a set of comparisons carried out under the auspices of Committee on Earth Observation Satellites (CEOS). These comparisons will aim to include all the world’s key research and measurement groups involved in satellite validation and will be the fourth in a series of five-yearly comparisons for the oceans (NPL also led the last comparison in 2010), but the first for Land and Ice.

As part of the laboratory phase of the comparisons, reference will be made to NPL and in part PTB standards to ensure a robust link and associated uncertainty to SI for all measurements can be established. The project will also include comparisons on the Ocean, the deserts of Namibia and probably the Arctic sea ice, as well as outside in the grounds of NPL. In addition to the measurements, a review of community methods will be undertaken with the view to establish a set of best practices on how traceability can be established and optimally maintained. The project will be led by NPL and will include collaborators from University of Southampton, Rutherford Appleton Laboratory, Scottish Marine Institute, Karlsruhe Institute of Technology, the Danish Meteorological Institute and PTB in the main to provide domain specific expertise to the NPL team.

The project is the latest addition to a rapidly-increasing portfolio of externally-funded projects reflecting the community awareness of the need to establish SI traceability and QA for Earth Observation and Climate. The success of these projects, underpinned by the UK National Measurement System (NMS) and the work of the Centre of Carbon Measurement, demonstrates the international leadership role that NPL has in meeting the needs of this critical sector.