Monitoring the Earth’s skin heat for crops and climate

Sponsored content: The European Space Agency joins forces with the US’ NASA on a mission to understand and predict the changing climate

Global Land Surface Temperature (Sentinel-3A data) is an Essential Climate Variable that describes processes such as energy and water exchange between the land surface and atmosphere, and plant growth. (Image: ESA)


A bright red twin-engined plane, equipped with ultra-high-resolution thermal imaging technology, has been scouring the agricultural heartlands of Europe this summer.

This was no search and rescue exercise, but the initial step towards building a proposed new satellite system capable of recording the temperature of the Earth’s skin in intricate detail.

The objective is to work towards increasing the resilience of agriculture to future water scarcity and variability, but will also deepen our understanding of Earth’s climate system.

The instrument on board, called HyTES, is an advanced thermal imager built by Nasa’s Jet Propulsion Laboratory. It has been surveying agricultural and urban areas in the UK and Italy as part of a joint airborne campaign between the European Space Agency (ESA) and Nasa – the American space agency.

The results will help to specify, and provide test data, to support the development of the proposed Land Surface Temperature Monitoring (LSTM) mission, which is being considered as an element of Copernicus, an Earth Observation programme managed by the European Commission – and to be designed and developed by ESA.

“These test flights are helping to specify the best spectral band positions to be adopted by the eventual satellite mission,” said Dr Darren Ghent, of the University of Leicester and a member of the LSTM Mission Advisory Group. He noted these test data will help his team develop the algorithms for producing accurate thermal maps of the land surface.

From a low-Earth, polar orbit, the proposed Copernicus LSTM mission will map both land surface temperature and rates of evapotranspiration, comprising the water vapour emitted by growing plants in unprecedented field-scale detail. It will deliver information at a 50 meters resolution, 400 times finer than currently operationally acquired from space-based thermal instruments such as the Sea and Land Surface Temperature Radiometer on Copernicus Sentinel-3.

Land surface temperature across France during the recent June heatwave taken by Copernicus sentinel-3A (the white is cloud cover and snow over the Alps). (Image: ESA)

“In an urban context, this will help to understand and model thermal activity and ventilation in and around individual cities and inform planning and ‘climate-adaptive’ building design, to deal with heatwaves such as those experience in western Europe during June.”

The data however will be equally, if not more relevant, in a rural setting, with major benefits relating to food production and sustainable water use, adds Dr Ghent.

“At the expected resolution it will be possible to monitor the temperature of individual fields, enabling growers to tailor irrigation regimes to specific crops and locations.”

He explains that, “under water stress, plants reduce or cease the rate of water loss from their leaves reducing the productivity of the crop. This is closely correlated with the land surface temperature, which can be detected from space before visible symptoms appear in crops. Being able to detect the problem and irrigate will help to underpin production,” adding that, “the observations from space provide global coverage and global benefits.”

The population of the Earth is expected to surpass nine billion by 2050, a 30% increase from today and will place pressure on finite water resources in the future.

“Agriculture already accounts for 70% of global freshwater, yet increased water withdrawals to keep up with future food demand combined with water scarcity and variability issues due to the effects of climate change will be challenging.

“The field-level temperature information from LSTM will increase the efficiency of individual farms in a changed environment.”

As well as facilitating management of individual farms, Dr Ghent highlights that the proposed mission underpins a number of UN Sustainable Development Goals relating to food security, sustainable water management and actions to combat climate change and its impacts.

Land surface temperature is an Essential Climate Variable and provides the UNFCCC and IPCC with the empirical evidence to better understand and predict the evolution of climate.

Accurate knowledge of the Earth’s skin temperature using satellite-derived information helps to explain the physics at the land-surface, and how energy and moisture are exchanged between the Earth’s surface and the air above it. This exchange is important for monitoring drought, changes in vegetation and the stability and extent of permafrost.

Existing land surface temperature datasets already provide an independent reference point for measurements taken from ground-based meteorological stations that have traditionally been used to describe average rates of global warming and by computer models to predict future climate. This has enabled scientists to compensate for bias and fill in gaps where weather stations are few and far between, particularly in polar regions, “where coincidentally the rate of warming is well above the global average,” says Dr Ghent.

A research team, led by the University of Leicester, is already working to develop and extend the existing data records of land surface temperature by merging datasets from a variety of satellites, including ones no longer in operation as part of ESA’s Climate Change Initiative.

2018 heatwave (Image: ESA)

The current data record stretches 25 years from 1992 to 2017, but will be extended to 2020 by merging data from the SLSTR instrument onboard the Copernicus Sentinel-3 satellite, with supplementary data from polar and geostationary satellites to characterise diurnal variation.

Increasing the length and accuracy of climate data records is vital for climate researchers, allowing them to detect small changes in climate with greater confidence.

By running campaigns from a plane, ESA and the European Commission are starting their journey to develop an Earth observation mission that supports efforts to increase resilience to future climate change at a resolution that will not only help to understand the role played by the temperature of the Earth’s skin but also to act to mitigate the increasing water scarcity caused by climate change.

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