EVALUATION OF TWO MESOSCALE MODELING SYSTEMS USING DIFFERENT CHEMICAL MECHANISMS

High levels of photochemical pollutants, like ozone, frequently affect south European countries and the concern with this subject substantially increased during the last decade. In the West coast of Portugal, where the human activities are concentrated, several episodes of photochemical pollution have been verified (Borrego et al., 2000). This coastal zone is strongly influenced by the nearby Atlantic Ocean, with frequent sea/land breeze circulation. Aiming to contribute to a better understanding of these mesoscale phenomena a field campaign was carried out in a coastal region, Aveiro, from 25 June to 2 July of 2001, which covered the last ozone episode noticed in the region. Measurements of all the main meteorological parameters and of ozone and its precursors concentrations were taken at surface in five different locations and in altitude. In addition, two mesoscale modeling systems (MEMO-MARS and MAR IV), with three different chemical mechanisms (EMEP, KOREM and CB-IV) were applied to the study area, for the two most representative days of the field campaign. The main purpose was to investigate the origin and formation of the measured high air pollution levels, to evaluate these systems, and to analyze the influence of the chemical mechanism type in the simulations.