Characteristics of the urban thermodynamic island and the energy balance on Toulouse (France) during winter and spring periods of the CAPITOUL experiment

CAPITOUL (Canopy and Aerosol Particles Interactions in TOulouse Urban Layer) is a one-year field campaign over the city of Toulouse (South west of France) which aims to study the impact of the urbanized areas on local meteorology. Numerous instruments have been set up to document this impact: flux measurement stations (at urban and rural sites), temperature profiling from street level up to 30 meters above roof level, temperature and moisture urban network, and wind profilers. We will present measurements made during winter- and springtime because these periods are not commonly studied in urban meteorology. The analyses show that sensible heat flux remains upward during nighttimes because of anthropogenic heat release. As a consequence, the temperature profile above roof levels stays neutral or even unstable at night. The latent heat flux is compared between urban and rural sites, during dry and rainy periods. The CO2 source resulting from human, urban activities is quantified. Measurements of urban thermodynamic island give a rather concentric shape around the old core of the city but with peculiarities resulting from differences in temperature and/or moisture between different urban class zones (high buildings, individual housing, commercial areas) in the agglomeration.