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Abstract: The thermodynamic exchanges of the old city center of Marseilles during a summer period are analyzed with the SOLENE thermo-radiative model, using measurements of the UBL-ESCOMPTE experimental campaign in June–July 2001. The selected scene is an actual fragment of the urban canopy composed of 4 streets at right angles, with various 19th century houses and yards. The SOLENE software’s ability to simulate the heat and radiation exchanges of this urban district with the atmosphere is first evaluated by comparing simulation outputs with surface temperatures of individual roof and façade elements measured by infrared radiation thermometers and with integrated fluxes measured on top of a neighboring meteorological mast. This model assessment is reinforced by a sensitivity study to the interior building temperature, a variable of possible influence which is usually not measured in studies at the scale of an urban fragment or district. The flux sensor position influence on the comparison is also studied by introducing a virtual sensor in the simulated scene. The software is further used to analyze the behavior of individual surface elements of the scene with various orientations during a typical summer diurnal cycle. The contributions of the different surface classes (roofs, façades, streets, yards) to the upward radiation and heat fluxes to the atmosphere are then detailed for several canopy morphologies (H/W). [Copyright &y& Elsevier]

The UBL/CLU (urban boundary layer/couche limite urbaine) observation and modelling campaign is a side-project of the regional photochemistry campaign ESCOMPTE. UBL/CLU focuses on the dynamics and thermodynamics of the urban boundary layer of Marseille, on the Mediterranean coast of France. The objective of UBL/CLU is to document the four-dimensional structure of the urban boundary layer and its relation to the heat and moisture exchanges between the urban canopy and the atmosphere during periods of low wind conditions, from June 4 to July 16, 2001. The project took advantage of the comprehensive observational set-up of the ESCOMPTE campaign over the Berre–Marseille area, especially the ground-based remote sensing, airborne measurements, and the intensive documentation of the regional meteorology. Additional instrumentation was installed as part of UBL/CLU. Analysis objectives focus on (i) validation of several energy balance computational schemes such as LUMPS, TEB and SM2-U, (ii) ground truth and urban canopy signatures suitable for the estimation of urban albedos and aerodynamic surface temperatures from satellite data, (iii) high resolution mapping of urban land cover, land-use and aerodynamic parameters used in UBL models, and (iv) testing the ability of high resolution atmospheric models to simulate the structure of the UBL during land and sea breezes, and the related transport and diffusion of pollutants over different districts of the city. This paper presents initial results from such analyses and details of the overall experimental set-up. [ABSTRACT FROM AUTHOR]

Presents a numerical simulation of traffic pollution in a street of Nantes, France. Method used to measure the distribution of pollutant concentrations.

Abstract: Measurements of thermal infrared (TIR) directional anisotropy (difference between off-nadir and nadir brightness temperatures) performed over the city of Toulouse using a method based on the use of 2 airborne TIR cameras are presented. Results from 3 flights at different times during a summer day (July 15th 2004) and from 1 flight in winter (February 25th 2005) all confirm important anisotropy (up to 10°C) and hot spot effects as previously reported in literature. A simple simulation approach is then proposed. It is based on the aggregation in any viewing direction of 6 directional temperatures (sunlit/shaded walls/streets/roofs) weighted by their corresponding surface ratios within the scene viewed. The city is described by 18 canyon streets oriented in all directions by 10° steps and the 6 temperatures are determined by integrating simulations of the energy balance model SOLENE repeated for the 18 canyon streets. The surface ratios are computed from images of the studied area generated with the POV-Ray software (Persistence of Vison Raytracer, http://www.povray.org/). This method is described in detail. The modelled anisotropy compares favourably with the measurements on all dates, despite a systematic underestimation ranging between 15 and 30%. The possible sources of discrepancy including sensitivity to the aspect ratio and to the surface parameters and possible impact of microscale structures are briefly discussed and several improvements of the modelling system are suggested. [Copyright &y& Elsevier]