Energy enters, passes through and leaves a city in several ways and in numerous physical states and forms (fuels, electricity, radiation and heat). The Urban Energy Budget (UEB) includes the anthropogenic heat flux (resulting from vehicular emissions, space heating and cooling of buildings, industrial processing and metabolic heat release by people) and therefore reflects the functionality of the city. Consequently, UEB is an important parameter for urban planning and design that should be taken into account in urban interventions aiming to improve thermal comfort and energy efficiency. Both urban planning and Earth System Science communities need spatially disaggregated UEB data, at neighbourhood scale. Such information is practically impossible to derive by in-situ fluxes measurements, whereas the potential of Earth Observation (EO) to provide UEB patterns at local scale (i.e. 100 m x 100 m) was unexploited. Thus, the main problem being addressed by the URBANFLUXES project is the innovative exploitation of satellite observations to estimate UEB spatiotemporal patterns at local scale.
URBANFLUXES generated novel methods for estimating spatiotemporal variations of UEB components, enabling its integration into applications and operational services. Τhe project met its objectives by developing EO-based approaches for estimating each UEB component separately, under the assumption of limited advection, using also standard meteorological observations from the Wireless Sensors Networks that were deployed in the three cities: London, Basel and Heraklion. In the general case however, the energy balance closure still remains challenging, leading to underestimations of the turbulent sensible heat flux and therefore of the anthropogenic heat flux. Therefore, beyond its important findings, URBANFLUXES has opened new research questions related to more robust EO-based estimation of the anthropogenic heat flux in complex urban settings, where the inherent uncertainties in estimating aerodynamic resistance make the assessments of the turbulent sensible heat flux challenging.