Role of Urban Plan Quality and Land Surface Characteristics in Urban Heat Island Outcomes

Abstract

As climate change continues to intensify temperature extremes across the world, understanding the impacts of extreme heat events and planning strategies for heat adaptation and mitigation are critical to human wellbeing. Urban populations are especially vulnerable to heat waves due to the urban heat island (UHI) effect and social and economic inequities. Under this effect, a lack of greenery and a greater area of heat-absorbing, nonpermeable surfaces cause cities to have higher temperatures than surrounding rural areas, which can have severe health consequences. In this study, I ask how cities are preparing for heat, how their temperatures and UHIs change over time, and what we can link to these changes. To do this, I evaluate and compare recent climate-related plans of six American cities using criteria designed to gauge how effective one would expect them to be in mitigating the local UHI effect and improving health outcomes. I also conduct a remote sensing analysis to examine the land surface temperatures (LSTs) of the urban cores and rural surroundings of these six cities, percent built-up or urbanized areas, and prevalence of vegetation over the past 20 years in summer and fall, and I see what connections can be drawn between the two. I find that even among ambitious cities known for being proactive in planning for climate change, there is a great variety in quality in their plans and policies for urban greening, and plans with well thought out implementation and monitoring processes and details give the city a much greater chance at achieving its goals. Even among the cities studied here, with their relatively similar climates, there is a great variety in UHI magnitude, and the most prominent driver of UHI magnitude appears to be background climate. Hottest temperatures and intensities of the UHI effect do not necessarily correspond with the best planning for heat in order to address this, and analysis is limited by the timespan studied, where planning efforts to prepare for climate change and mitigate heat may still need much more time in order to see substantial results.