Urban Heat Island: Mechanisms, Implications, and Possible Remedies

TLDR

Urban heat islands cause higher temperatures in cities than surrounding rural areas because built‑up surfaces absorb and store more solar energy, leading to daytime and nighttime heat increases, higher air‑conditioning demand, poorer air and water quality, shorter pavement life, and intensified heat waves. The study calls for further research into dynamic surface emissivity control, material property adjustments, and the health and socioeconomic effects of urban heat islands. Potential mitigation strategies include altering roof and pavement thermal properties and emissivity, and expanding urban vegetation. Quantitative analysis indicates that cool roofs are the most cost‑effective mitigation approach.

Abstract

Urban heat island (UHI) manifests as the temperature rise in built-up urban areas relative to the surrounding rural countryside, largely because of the relatively greater proportion of incident solar energy that is absorbed and stored by man-made materials. The direct impact of UHI can be significant on both daytime and night-time temperatures, and the indirect impacts include increased air conditioning loads, deteriorated air and water quality, reduced pavement lifetimes, and exacerbated heat waves. Modifying the thermal properties and emissivity of roofs and paved surfaces and increasing the vegetated area within the city are potential mitigation strategies. A quantitative comparison of their efficacies and costs suggests that so-called cool roofs are likely the most cost-effective UHI mitigation strategy. However, additional research is needed on how to modify surface emissivities and dynamically control surface and material properties, as well as on the health and socioeconomic impacts of UHI.