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Cities are notably warmer than their surroundings because urban structures absorb and trap more solar and thermal radiation than open land or vegetated and forested areas.
The results of the EU-funded URBANFLUXES project will help authorities monitor, test and act on city heat problems through sustainable urban planning, as well as targeted actions during peaks and heatwaves.
Anthropogenic heat caused by human activities like transport, industry and even spent body heat creates an urban heat island (UHI), which contributes to global warming. The UHI effect, coupled with heatwaves, which are expected to occur more often, leads to increased energy consumption (through air-conditioner use, for example), greater discomfort for populations and more deaths.
URBANFLUXES researchers studied this phenomenon by breaking down urban energy use and targeting man-made heat fluxes. They used Earth-observation (EO) imagery, taken from satellites, and combined the results with conventional meteorological measurements at street level. This satellite-based approach proved valuable in tracing heat signatures down to the local (100m x 100m) level, and can be applied to any city.
Data from the skies
Anthropogenic heat flux, or QF, is the change in heat resulting from vehicle emissions, space heating and cooling of buildings, industrial processing and heat released by people and animals living in the city. Urban planners and scientists need detailed QF data, down to the streetscape and neighbourhood level, as well as city-wide scales.
Such information is almost impossible to get from street-level measuring systems alone. The satellite remote-sensing tools used by scientists carrying out EO studies, like climate change modelling, enable researchers to estimate and mitigate the UHI effect more accurately.
The project established solid EO readings for use at the local or urban scale. This approach is transferable to any urban setting and can provide benchmark data for different applications, including climate models to assess the implication of the man-made heat fluxes and energy models that hone in on specific buildings. The data also feed decision-support systems for urban sustainable planning and mapping of emissions related to energy consumption. .