Thermal Hot Spots in Cities as Hazards for Health Security: An Application for the Urban Agglomeration of Athens, Greece

Urbanization affects dramatically the thermal environment of cities. The increase of impervious surfaces alongside with anthropogenic heat sources and the reduction of vegetated areas lead to elevated air and land surface temperatures and consequently to considerable public health risk. In this study a typology for thermal hot spots, that is areas in cities where higher than average land surface temperatures are consistently observed, is developed and applied – with the use of earth observation and ground data – for the city of Athens. Supervised classification is used to map the types of land cover in the study area, land surface temperatures are estimated using multi-seasonal satellite images (for specific synoptic conditions), and ground measurements of air temperature were used to establish a thorough understanding of the thermal environment. Results indicate that several hot spots exist (in some cases maximum surface temperatures exceeded 47°C in the summer months), especially in urban dense areas, the historic center of Athens and the industrial zone of the city. The recognition of thermal hot spots is important as they are practically urban hazards for health security, taken that they reflect areas where thermal comfort is reduced and photochemical air pollution is enhanced. Interventions in these areas are necessary for health security