Cooling trajectories in Commercial areas for Urban Heat Island (UHI) mitigation

Climate change and rising temperatures are established facts, forcing cities to face a reality to which they must adapt. "On June 28, 2019, a temperature of 45,9°C was recorded at a weather station in France, exceeding the country's previous temperature record; set during the infamous 2003 heatwave; by almost 2°C" (Mitchell, D & al. 2019). Several studies have also established that heatwaves were enhanced by human-induced climate change and activities (Mitchell, D & al. 2019). Therefore, it is crucial to develop clear local plans to adapt to and mitigate the impacts of these heatwaves, which are directly associated with increased heat-related mortality.

This study aims to determine tools to analyze various cooling trajectories. It is centered on commercial areas, which are mostly vast territories on the outskirts of cities. These zones emerged around 1960, often at city entrances near highway interchanges, and are directly connected to regional or national roads (Verhetsel, A. 2019). They often include shopping centers where marketing and consumption dominate. The urbanization of the suburbs by middle class residents and the rise of car use contributed to their emergence. The principle of "no parking, no business" governs the spatial organization of these areas (Kervran, P. 2021). Therefore, commercial zones also contribute to the climate change adaptation trajectories of the city. 

The urban heat island effect is an important factor to consider when talking about climate change and heatwaves. Therefore, urban cooling strategies play a crucial role in studying climate change adaptation. Cities are very different in their organization, density, size, and history, but they all share a common denominator: human beings. Which also means that discussing thermal comfort for users, both during and outside of heatwaves is very important in urban areas (Abdollahzadeh, N., & Biloria, N. 2020; Aghamolaei, R. 2022). This raises other challenges, such as managing and maintaining the solutions implemented for climate adaptation. Also, several studies have shown many cooling solutions to be very effective and the ADEME (Agence de la transition écologique - Agency for ecological transition in France) has published a document presenting various solutions supported by measurements and data to combat urban overheating. It has classified them in three main groups :  the nature-based "green and blue", the "gray" solutions, and the soft solutions. We can therefore say that effective solutions exist and that the current challenge lies primarily in more frequent implementation. However, for these solutions to function optimally and achieve urban cooling, it is necessary to consider the components of the larger urban system (ADEME, 2021). Also, to understand the functioning of a city, it is important to understand it's urban dynamics. These are often composed of interrelations around a decision-making center, with several overlapping urban components (PAULET Jean-Pierre, 2009).

The overall goal of this study is to create a detailed understanding of how urban cooling solutions evolve over time, how they interact with stakeholders, and how they contribute to the urban system. 

Keywords: climate change, urban heat island, cooling solutions, trajectory, mitigation, adaptation, commercial areas.