A heat island study of Athens using high-resolution satellite imagery and measurementsof the optical and thermal properties of commonly used building and paving materials

In this study, high-spatial resolution multispectral satelliteimages collected over the metropolitan Athens area in Greece are used to generate a) a broadband albedo map depicting the albedo spatial variations across the metropolitan area, b) a vegetation cover map showingthe spatial distribution of urban vegetation and c) a daytime and night-time surface temperature map depictingthe spatial variations of the surface temperature across the city. From these maps cooling and heating regions are identified and analyzed to reveal relationshipsbetween heat islands and urban surface characteristics.Based on the data acquired with the use of satelliteimages and in order to better define the heat island problem and the mitigation measures that need to be taken, the most common building and paving materials used in the urban fabric are examined. Their optical and thermal properties were measured using a UV/VIS/NIR spectrophotometer fitted with an integrating sphere, an emissometer. The Solar Reflectance Index of the samplesis calculated in order to characterize them as cool or warm. Cool materials, with high albedo and thermalemittance values attain lower surface temperatures when exposed to solar radiation, reducing the transferenceof heat to the environmental air.