Keeping a watch on sea surface temperature

Sea surface temperature data are crucial for operational weather forecasting, operational ocean forecasting and for monitoring the Earth’s climate.

Thursday, 05 April 2018

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The launch of Sentinel-3B at the end of April, with its suite of ocean-monitoring instruments, is expected to make a significant impact on the accuracy and relevance of sea surface temperature data available for those purposes.

The spacecraft is part of a series of Sentinel satellites under the umbrella of the EU’s Copernicus programme, which takes a continuous “health check” of our planet.

Sentinel-3A was launched in February 2016 and the successful launch of Sentinel-3B will represent the full deployment of the Sentinel-3 mission.

EUMETSAT operates the Sentinel-3 satellites, in cooperation with the European Space Agency (ESA), and processes marine data and products for delivery to users. ESA processes and disseminates the satellite’s land observations.

One of the instruments on board the spacecraft is the Sea and Land Surface Temperature Radiometer (SLSTR).

EUMETSAT Sea Surface Temperature Expert Anne O’Carroll said that since the launch of Sentinel-3A, the instrument, currently the most advanced of its kind, has been delivering a data flow of outstanding quality.

“The greater accuracy and higher quality of data delivered by the SLSTR is owed to its design,” O’Carroll said.

“The instrument takes a dual view of its path as it orbits the Earth, as well as having on board two infrared sources able to continually compare and calibrate the measurements.

“Both taken together result in more accurate data. This is much appreciated by the user community.”

O’Carroll said the SLSTR is a source of data of such high quality that users are developing plans to use it to correct other sea surface temperature data sources.

Ensuring the required data quality is key to O’Carroll’s work but over and above carrying out data validation in house, based on EUMETSAT’s proven algorithms, a lot of activities are coordinated by partners such as the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI SAF) and ESA’s Sentinel-3 Mission Performance Centre (MPC).

OSI SAF products are used for operational weather forecasting, operational marine meteorology, operational oceanography, polar research, research in meteorology and oceanography and monitoring of the environment and climate.

Other external data, especially those from drifting buoys and ARGO floats, are vital for verifying the accuracy of satellite measurements.

“We need other data to assure the quality of our measurements and establish what uncertainties we might be dealing with,” O’Carroll said.

“That means, we truly need to understand the characteristics of our data. Only if we are convinced we have the best possible datasets can we provide the information to our users."

“Given that we are dealing with operational datasets, this is not only a long-term, but a continuous, process."

“We need to ensure that the reference sources we compare against are as reliable as possible and, for drifting buoys, that can be a problem."

“After a decade of discussions, we just started an exciting project, which will give us fiducial reference temperature measurements for sea surface temperature. A new Copernicus project will place better sensors on 100 to 150 of their buoys, which in turn will help us verify our own data.”

O’Carroll said expectations are high for the period after the launch of Sentinel-3B.

“Two SLSTR instruments with their 750km swath over the dual-view capability will make a massive impact on the accuracy and relevance of global datasets where SLSTR can then be used as the reference for other sea surface temperature missions,” she said.

“A second Sentinel-3 will help to further improve the accuracy of hurricane path predictions and related warnings, as well as the impact assessments for coastal communities on water quality or sedimentation.”

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