Abstract
Cities worldwide are getting warmer due to the combined effects of urban heat and climate change. To this end, local policy makers need to identify the most thermally vulnerable areas within cities. The Local Climate Zone (LCZ) scheme highlights local-scale variations; however, its classes, although highly valuable, are to a certain extent generalized in order to be universally applicable. High spatial resolution indicators have the potential to better reflect city-specific challenges; in this paper, the Urban Heat Exposure (UHeatEx) indicator is developed, integrating the physical processes that drive the urban heat island (UHI). In particular, the urban form is modeled using remote sensing and geographical information system (GIS) techniques, and used to estimate the canyon aspect ratio and the storage heat flux. The Bowen ratio is calculated using the aerodynamic resistance methodology and downscaled remotely sensed surface temperatures. The anthropogenic heat flux is estimated via a synergy of top–down and bottom–up inventory approaches. UHeatEx is applied to the city of Athens, Greece; it is correlated to air temperature measurements and compared to the LCZs classification. The results reveal that UHeatEx has the capacity to better reflect the strong intra-urban variability of the thermal environment in Athens, and thus can be supportive for adaptation responses. High-resolution climate projections from the EURO-CORDEX ensemble for the region show that the adverse effects of the existing thermal inequity are expected to worsen in the coming decades.
Highlights
Over two-thirds of the world’s population are projected to dwell in urban areas by 2050 [1], reflecting the continuously growing role of cities as centers of human and economic activity.Among other environmental concerns, such as ambient/indoor air pollution and waste management, cities experience elevated air temperatures relative to their surrounding rural areas [2], which is a phenomenon commonly referred to as the urban heat island (UHI)
Global climate change further exacerbates the impact of the UHI, as it causes the warming of the climate system and makes the future occurrence of heat waves with higher frequency and duration very likely [18]
Mitigation/adaptation are being interlinked with climate change policies [19], and cities are gaining a central role in current global agreements, such as the recent Paris Agreement (2015) of the United
Summary
Over two-thirds of the world’s population are projected to dwell in urban areas by 2050 [1], reflecting the continuously growing role of cities as centers of human and economic activity.Among other environmental concerns, such as ambient/indoor air pollution and waste management, cities experience elevated air temperatures relative to their surrounding rural areas [2], which is a phenomenon commonly referred to as the urban heat island (UHI). Over two-thirds of the world’s population are projected to dwell in urban areas by 2050 [1], reflecting the continuously growing role of cities as centers of human and economic activity. The thermal effect of a city is mainly related to [3]: (a) the urban form—the fabric, the surface cover, and the three-dimensional urban structure—and (b) the urban function—the waste heat resulting from human activities. Global climate change further exacerbates the impact of the UHI, as it causes the warming of the climate system and makes the future occurrence of heat waves with higher frequency and duration very likely [18]. Initiatives for UHI mitigation/adaptation are being interlinked with climate change policies [19], and cities are gaining a central role in current global agreements, such as the recent Paris Agreement (2015) of the United
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