Abstract
The purpose of this work is to study the impact of an urban land cover on local meteorology and spatial distribution of atmospheric pollutants over the Paris region. One anticyclonic episode from the ESQUIF campaign was simulated using the meso-scale meteorological and chemical Meso-NHC model coupled to the town energy balance (TEB) urban canopy model. A control simulation was also performed without implementing TEB in order to quantify the effect of the urban parameterization. Both meteorological and chemical model outputs were evaluated against the data collected during the experiment and most of the results are improved when TEB is applied. The simulation indicates the formation of an urban heat island (UHI) over Paris which is stronger at night than during day. The structure of the atmospheric boundary layer is also strongly influenced by the city. The present study shows that both nocturnal and diurnal urban effects have an important impact on the primary and secondary regional pollutants, more specifically the ozone and the nitrogen oxide (NO x ). The spatial distribution and the availability of pollutants are significantly modified by the urbanized area mainly due to enhanced turbulence.
Highlights
Due to growing urbanization and pollutant emissions, it was emphasized by Crutzen (2004) that, ‘it will be important to explore the consequences of combined urban heat and pollution island effects for meso-scale dynamics and chemistry’
The present paper studies the urban micrometeorology during a summertime anticyclonic episode associated with a high photochemical episode of pollution in the Paris region
Data collected during the IOP6 of ESQUIF campaign allow evaluation of the numerical simulations conducted with the m/s m/s (a) meteorological non-hydrostatic meso-scale model Meso-NHC
Summary
Due to growing urbanization and pollutant emissions, it was emphasized by Crutzen (2004) that, ‘it will be important to explore the consequences of combined urban heat and pollution island effects for meso-scale dynamics and chemistry’. At night under clear and calm conditions, a large temperature gradient develops between the city and its surroundings (Oke, 1982): such urban heat islands (UHI) were already documented for instance in Montreal (Oke and East, 1971), Paris (Escourrou, 1991), Toulouse (Estournel et al, 1983), Mexico (Oke et al, 1999) and Atlanta (Bornstein and Lin, 2000). Even if the UHI can be observed, the dynamic processes are preponderant compared to the radiative and thermal effects. The dynamic roughness of the city favours the production of turbulence and the development of the urban boundary layer (UBL) (Dupont et al, 1999)
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