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International audienceThe main purpose of this study is to propose a model that well reproduces the heat storage flux into urban ground as well as surface temperature evolution. For that purpose a complete bibliographic review is first achieved. Some lacks are identified and the methodology to define the model in agreement with the conclusions of the literature review is presented as well as the way to assess its performances. Three nodes distributions are proposed regarding ground temperature profiles using an analytic solution. A sensitivity study is achieved on a large number of parameters: the material properties, the size of the layers, the deep boundary condition, and the convective heat transfer coefficient. The model ability to reproduce heat conduction transfer is validated thanks to a measurement campaign realized on a large asphalt˚Corresponding parking lot during two clear and hot days. The RMSE between estimated and observed surface temperature is 0.75 0 C. The validation also include comparison with temperature at 4 different depths. The RMSE are 0.73 0 C, 0.48 0 C, 0.21 0 C and 0.06 0 C respectively at 5cm, 10cm, 34cm and 50cm. Performances obtained with the model using different nodes distributions are discussed and compared with results from the literature. The model presents better performances than most of others models applied in quite similar conditions. Finally, the application of the proposed model at a yearly scale demonstrates that the accuracy loss caused by the decrease of the nodes number depends on weather conditions. In particular, the most difficult days to simulate are clear and sunny days

Numerical simulation is a powerful tool for assessing the causes of an Urban Heat Island (UHI) effect or quantifying the impact of mitigation solutions on local climatic conditions. However, the numerical cost associated with such a tool, which may seem low for a section of mesh within the district geometric model, is quite significant at the scale of an entire district. Today, the main challenge consists of achieving both a proper representation of the physical phenomena and a critical reduction in the numerical costs of running simulations. This paper presents a combined parametric urban soil model that accurately reproduces thermal heat flux exchanges between the soil and the urban environment with a reduced computation time. For this purpose, the use of a combination of two reduced-order methods is proposed herein: the Proper Orthogonal Decomposition (POD) method, and the Proper Generalized Decomposition (PGD) method. The developed model is applied to two case studies in order to establish a practical evaluation: an open area independent of the influences of the surrounding surface, namely a parking lot, and a theoretical urban scene with two canyon streets. The mean surface temperature reduction error remains below 0.52˝C for a cut computational cost of 80%.