Dynamics of air pollution in the northwestern Mediterranean Bain (Catalonia) in summer using high-resolution air-quality modeling

Abstract

The complex behavior of photochemical pollutants in the northwestern Mediterranean Basin (NWMB) and Catalonia is conditioned by the superposition of circulations on different scales and on the pattern of emissions. This work combines the models MM5 (meteorological), EMICAT2000 (emissions), and CMAQ (chemistry transport model), which have been applied with very high temporal and spatial resolution (1 h and 2 km) to analyze the high levels of photochemical air pollution over the NWMB (Catalonia) during a typical summertime episode, in this study, 1316 August, 2000. This combination of models is shown to be well-suited to address the large range of scales involved. The study focuses on local as well as medium and large-scale processes controlling tropospheric ozone in the NWMB, notably, emissions and photochemistry, convective and advective transport, deposition processes, and stratosphere-troposphere exchange. In the lower troposphere, local re-circulation systems are of key importance, together with the complex pattern of emissions in Catalonia. The strength of the land-sea breeze circulation, together with thermally or mechanically driven convection over the complex orography of the eastern Iberian coast, can induce vertical transport and the layering of air pollution. These phenomena can be captured by simulations carried out for the domain covering the entire Iberian Peninsula (with a 1 h and 24 km resolution).