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ABSTRACT
In many micrometeorological studies with computational fluid dynamics, building-resolving models usually assume a neutral atmosphere. Nevertheless, urban radiative transfers play an important role because of their influence on the energy budget. To take into account atmospheric radiation and the thermal effects of the buildings in simulations of atmospheric flow and pollutant dispersion in urban areas, a three-dimensional (3D) atmospheric radiative scheme has been developed in the atmospheric module of the Code_Saturne 3D computational fluid dynamic model. On the basis of the discrete ordinate method, the radiative model solves the radiative transfer equation in a semitransparent medium for complex geometries. The spatial mesh discretization is the same as the one used for the dynamics. This paper describes ongoing work with the development of this model. The radiative scheme was previously validated with idealized cases. Here, results of the full coupling of the radiative and thermal schemes with the 3D dynamical model are presented and are compared with measurements from the Mock Urban Setting Test (MUST) and with simpler modeling approaches found in the literature. The model is able to globally reproduce the differences in diurnal evolution of the surface temperatures of the different walls and roof. The inhomogeneous wall temperature is only seen when using the 3D dynamical model for the convective scheme.
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1. Introduction
Interest in urban climatology has increased in the past decade. It corresponds to the thermal and dynamical airflow response to the urban system solicitations, resulting in radiative transfers and convective exchanges within the urban air and with the building walls (Grimmond and Oke 1999; Arnfield 2003). In the past few years, numerical studies have been conducted to solve the surface energy balance (SEB) in urban canopies, with different degrees of simplification, using either an integrated representation of the urban canopy (Masson 2000) or a threedimensional approach (Mills 1996; Miguet and Groleau 2002; Kanda et al. 2005; Krayenhoff and Voogt 2007; Gastellu-Etchegorry 2008; Asawa et al. 2008). Those models share the following parameterizations in their design: the schemes possess separate energy budgets for roofs, roads, and walls; radiative interactions between roads and walls are explicitly treated.
The Town Energy Balance (TEB) scheme of Masson (2000) consists of a facet-averaged scheme with one generic roof, one...