Chapter 1.6 Modelling urban heat island in the context of a Mediterranean city

Abstract

Abstract Urban heat island (UHI) is one of the most well known forms of localised anthropogenic climate modification. It causes a local alteration of atmospheric stability. According to a top-down methodology, mesoscale meteorological modelling is a commonly used approach to study the impact of UHI on atmospheric stability at the urban scale. Our work is an effort to investigate UHI using a bottom-up approach by looking at the UHI through a computational fluid dynamics (CFD) model applied to the street canyons of a neighbourhood area. The CFD code is set up to model the thermal response (structure surface temperature and ambient air temperature) of an urban system to the outside climate. The determination of the air temperature in an urban unit allows the calculation of the Δ T u−r factor representing the difference between the air temperature in the urban system (u) and the air temperature recorded at the closest meteorological station (r), generally situated in the countryside. This factor, introduced by Oke in Boundary Layer Climate, (1987), enables the analysis of the heat island generated by an urban system. The simulation results obtained from the CFD model allows the estimation of the Δ T u−r factor in relation to physical aspects and geometrical configurations. We apply this technique to study UHI of a Mediterranean city of which some urban temperature measurements and morphometry from a digital elevation model (DEM) are available.