Defining scales of the land use effect to map the urban heat island in a mid-size European city: Rennes (France)

The Urban Heat Island (UHI) is a climatic phenomenon linked to urbanization. In the context of climate change, municipalities have to adapt the city to increase in heat waves by managing the UHI. This study aims to map the UHI of a mid-size city (Rennes, France) and to define the relevant land use factors. The UHI was measured by 22 weather stations in different contexts: urban, suburban and peri-urban. After investigating the UHI weather conditions, we used a multi-criteria method by linear regression to build a model of the UHI. It explained 82% of UHI spatial variability for an average year. This method was automated to map the UHI for several periods (annual, seasonal, and daily). The influence of the land use on the UHI fluctuated with weather conditions. We tested different land use factors for several scales (100 m to 900 m). The results show the preponderance of low vegetation fraction and built-up fraction variables to explain the UHI with a buffer radius of 200 m and 900 m respectively. We conclude that these variables are relevant to define indexes for town planners.