De par ses caractéristiques, l’environnement urbain influe significativement sur le climat observé dans et à la périphérie des villes. Il est communément admis que le centre des villes présente fréquemment des températures d’air plus élevées que celles mesurées dans les zones rurales environnantes. Ce phénomène appelé îlot de chaleur urbain intéresse les enjeux relatifs à la santé publique, au confort urbain et à la demande énergétique. Ce travail de thèse propose de caractériser le phénomène d’îlot de chaleur à partir de l'association d'un zonage climatique et de mesures mobiles à haute résolution spatiale dans la canopée urbaine. Il repose sur une approche méthodologique en trois temps. Une classification climatique ("Local Climate Zones" (LCZ)) est tout d'abord appliquée à l'agglomération de Nancy. Ce découpage climatique du territoire sert de support à la réalisation de mesures embarquées effectuées en période estivale à l'aide d'un véhicule instrumenté. Celles-ci ont pour but d'observer in situ les spécificités climatiques des LCZ recensées dans l'agglomération. L'association d'une base de données de relevés météorologiques et de la classification LCZ permet de caractériser le comportement climatique du milieu urbain et de comparer le comportement de différentes typologies de quartiers en présence d'un îlot de chaleur urbain. Cette démarche propose également un cadre théorique pour le développement d'un modèle de diagnostic à partir d'indicateurs urbains et climatiques, avec la perspective de construction d'un outil de prise en compte de l'îlot de chaleur dans le processus de planification urbaine / Urban environment impacts significantly the climate observed within and around cities. In this context, city centers frequently present higher air temperatures than those measured in the rural areas nearby. This phenomenon called urban heat island impacts major issues such as public health, urban comfort and energy demand. This Ph.D. thesis proposes to characterize the urban heat island phenomenon based on the combination of a climatic zoning and high spatial density mobile measurements performed within the urban canopy layer. This study is divided into three steps. A climate classification ("Local Climate Zones" (LCZ)) is first applied to the conurbation of Nancy, France. This climatic zoning is used in order to perform mobile measurements thanks to an instrumented vehicle. These measurements target to observe the climatic patterns of the LCZ built in this conurbation. The combination of meteorological database and LCZ classification scheme allows to characterize the urban climate behavior and to compare the thermal behavior of different neighbourhood types. This approach provides a theoretical framework for the development of a diagnosis model based on urban and climatic indicators. It also brings outlooks regarding the building of a decision-support tool that aims to supply information about urban heat island adapted to the urban planners needs

This thesis investigates the impact of Green Infrastructure (GI) and Local Climate Zones (LCZs) on air temperature at 2 meters above the ground (T2m) in Norrköping and Linköping, Sweden, with a focus on urban planning and climate resilience strategies. Two concepts of LCZ and the newly developed “3-30-300” GI rule are applied. Two concepts are evaluated under summer 2018 strong heatwave conditions and project future scenarios with a 3°C rise in global temperatures during extreme heatwaves. The results show an increase in mean temperature of about 2.9 °C and an extended duration of heatwaves in 17 days from the summer of 2018 to the possible future. Findings indicate that urban areas adhering to 30% tree canopy coverage and within 300 meters or less of a park show a 0.7°C reduction in median T2m during heatwaves. LCZs with more natural environments and less paved surfaces, such as open low-rise, sparsely built, and open midrise, exhibit lower air temperatures, while densely built areas (compact high-rise) show higher temperatures at night, and wide-open paved areas (large low-rise, heavy industry) show higher temperatures during days. The study underscores the necessity of increasing GI coverage and parks in both cities, highlighting the challenges of equitable GI distribution. Recommendations for future research include selecting cooling-effective indigenous tree species and expanding the scope to additional climate variables. This work provides crucial insights for urban areas in Nordic countries and similar climates, contributing to sustainable urban planning and enhanced climate resilience.