Local to regional atmospheric modeling and aerosol lidar methods in the mediterranean

Resumen

This multidisciplinary study is mainly based on the combination of atmospheric modeling and aerosol lidar measurements to explore a variety of atmospheric processes-interacting from local to regional scales-in the Mediterranean troposphere. Observations and models show that summertime ozone (O3) and aerosol concentrations largely exceed the European Union air quality standards; and may exert a strong influence on the regional climate. The highly urbanized coastal areas exert a strong anthropogenic pressure giving rise-under strong insolation-to photochemical pollution episodes over the region. A coastline constitutes a step change in all surface parameters, which hampers the performance of air quality forecasts. Barcelona is an urban coastal city located in the Western Mediterranean Basin (WMB). As the mixing height is a key parameter for air quality modeling, the large Barcelona lidar database was analyzed to derive a mixing height climatology over the area. Three methods were tested. Typical summertime layering of aerosols introduces large biases using available methods. A reformulation of the Inflection Point Method with new application criteria improved the accuracy of the retrievals. In summer, mixing heights are mainly limited to 400 - 800 m due to large mesoscale compensatory subsidence over the sea and local thermal internal boundary-layer formation. In a second step photochemical modeling was conducted in the Barcelona geographical area for one episode to study the influence of three surface/PBL schemes (one local and two non-local schemes), on the predicted photochemical pollutant concentrations. Modeled mixing height, temperature, and wind speed and direction were evaluated with lidar and meteorological data in order to analyze the differences observed. Modeled daily maximum pollutants' concentrations varied in magnitude and location in function of the PBL scheme and PBL height diagnosis method used in the model. Mainly, the