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The thermo-radiative model LASER/F aims at computing the energy balance of a district. The components of the urban fabric are represented in vectorial 3D and the scene is fragmented into small elementary triangular facets of a few square meters. The physical processes related to the energy balance are solved for each facet. The operational framework of the model is briefly presented in this paper, as well as the numerical procedures and the physical concepts used for the different types of urban elements. The energy balance of a neighborhood of Strasbourg (France) is then simulated. The results are compared with experimental field measurements and the model accuracy is evaluated with a complete set of statistical indices. The model obtains globally a good level of performance for almost all variables, except the latent heat flux.

Thermal remote sensing has become widely used to monitor and study Urban Heat Island (UHI) by the use of satellite Land Surface Temperature (LST) data, and the Local Climate Zone (LCZ) scheme has established itself as the standard for assessing Urban Heat Island Intensity (UHII). A lot of research on LST-LCZ relationship has been done, but mainly in flat terrain. Some studies on UHI in mountainous areas have been conducted, but most of them considered the combined effect of land use/land cover and topography on temperature. To the best of our knowledge no study has been carried out on the LST-LCZ relationship in a complex topography area after removing the topography effect. This paper presents a methodology for assessing the impact of the urban structure on UHII in Beirut, a coastal city with heterogenous urban morphology and complex topography. It was concluded that the main urban variables which contribute to the spatial variability of topographically normalized LST are, in decreasing order of relative importance, the built-up ratio, the pervious surface ratio, the buildings' mean height and mean surface area. The difference in average temperatures between high-rise densely built LCZs and mostly pervious zones exceeded two degrees at nighttime.