Impact of artificial surfaces on Urban Heat Island (UHI) effect on the city of Louvain-la-Neuve : study of the thermal radiance of materials and possible differentiation of surfaces from a TIR image

Details

Supervisors

Defourny, Pierre ; Radoux, Julien

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

The global climate has shown signs of change, such as increasing temperatures, altered precipitation patterns and a higher frequency of extreme events. In addition to rising temperatures and the increasing frequency of heat waves, cities will be more vulnerable due to the urban heat island (UHI) effect. The UHI effect is characterised by higher air temperature in urban areas compared to surrounding rural areas. This difference in temperature is mainly due to the transformation of natural surfaces into artificial ones, anthropogenic heat release, and urban design that alters the energy balance. The disruption of the energy balance varies according to the types of urban development and the properties of their materials. Given the several impacts of this phenomenon on human health, energy consumption, biodiversity and so on, it is crucial to understand the factors contributing to this effect. This study aims to contribute to a better understanding of these factors in Louvain-la-Neuve. Therefore, this study focuses on the different surface materials used in the city of Louvain-la-Neuve. The main objective of this study is to assess the thermal radiance of different types of artificial surfaces that contribute to the urban heat island effect. This is done using a thermal infrared (TIR) map. The study also aims to determine whether it is possible to recognise surface materials based on their thermal radiance from a thermal infrared image. The current study has analysed the possible effect of the particularities of the city of Louvain-la-Neuve on the thermal radiance values. The platform on which the centre of the city is built has a slight effect, causing an increase in the thermal radiance value. However, it appears that there is no other effect of microclimate. Nevertheless, shading effect and insulation effect have been observed and must be taken into account when selecting pixels to determine valid thermal radiance values. The results of the study show that the analysis of TIR images can establish a clear distinction between thermal radiances of different roof types, including ceramic, slate, flat roof and solar panel. The ceramic roof exhibits a higher thermal radiance value compared to slate roof. The flat roof and solar panel exhibits higher thermal radiance values than the two other roof types. Concerning the ground coverings, asphalt, concrete and cobblestones exhibit a similar thermal radiance value, which is significantly higher compared to the value of roof materials. Therefore, based on the TIR images, ground covering can easily be identified compared to roof coverings. The study reveals that, in general, the TIR image appears to be relevant in distinguishing surface materials, thanks to the different thermal radiance values . TIR appears to be particularly advantageous in discriminating metallic and wood surfaces compared to optical images.