The DAURE field campaign: meteorological overview

Abstract. From end of February until March 2009 and July 2009 the experimental campaign named DAURE took place in northeastern Spain in both an urban and rural sites (Barcelona city and Montseny Natural Park) with the main objective of studying the formation and transport processes of particulate matter in the region. Several groups collaborated in an extensive measurement campaign with aerosol monitoring, meteorological measurements, atmospheric vertical structure retrievals from LIDAR and supported by numerical simulations of the meteorological and air quality conditions over the region. In this article, we present a description of the main meteorological conditions that affected the Barcelona geographical area during the campaign. The main synoptic conditions are identified and discussed by means of meteorological observations and numerical weather prediction models. Furthermore, a detailed analysis of the local meteorological conditions during the campaign is also presented. The characteristic surface wind field and the vertical structure of the main flows affecting Barcelona and the Montseny rural site are discussed using high-resolution mesoscale meteorological simulations, vertical profiles of LIDAR measurements, radiosoundings, and analysis of backward dispersion simulations with a Lagrangian model. The analysis permits the identification of three main meteorological regimes for the winter campaign (February and March 2009): a first regime dominated by high-pressure conditions over Barcelona and western Mediterranean Basin, high insolation, and the development of thermally-driven wind flows. A second regime is characterized by a strong northwestern advection that produced a cleansing action over the atmosphere. And a third identified regime is dominated by strong stagnant conditions produced by thermal inversions that decouple the low troposphere of plain and coastal areas from mountainous terrains. On the other hand, the main meteorological regimes identified for the summer campaign (July 2009) are: a typical summer recirculation pattern, with low pressure gradients over the western Mediterranean basin, high insolation and development of mesoscale features, a second pattern characterized by the advection of southern air masses enriched with mineral dust from North Africa, and a third zonal advective scenario associated with frontal systems that inhibits the mesoscale circulations and leads to some precipitating events over northeastern Spain. Finally, a classification of the main dispersion patterns deduced from backward Lagrangian simulations is presented and discussed. The results help identify the main flow patterns that lead to the formation and accumulation of particulate matter within the boundary layer, and may produce high pollutant concentrations at Montseny or Barcelona sites. During the DAURE winter and summer campaigns, typical meteorological conditions that lead to air pollution episodes of particulate matter within the Western Mediterranean Basin were observed.