Importance of local meteorology in coastal ozone dynamics: a case study

摘要

Ozone dynamics are strictly dependent to meteorological conditions. Solar radiation, pressure distribution and horizontal wind field, along with precursor concentrations, play fundamental roles in ozone formation and depletion. The present case study concerns Falconara, an Italian town located on the Adriatic sea, which presents several air pollution modelling issues: complex orography, location at the mouth of Esino river and the presence of several distributed and point precursor sources. During the summer 2000 strong ozone episodes have been recorded in disagreement with other typical pollution concentration levels. The aim of our work was to investigating the role played by meteorological scenarios that may favour ozone formation, stagnation and recirculation. For this purpose RAMS simulations have been implemented by assimilating data from provincial monitoring network and from European Center for Medium-range Weather Forecast elaborations. The simulation domain is represented by four regular nested grids: the first grid is an 18x18 mesh with a 50000m side width; the finest grid is a 37x37; the four nesting ratios are respectively 1,5,5,5. Simulations have been carried out for three significant days in the month of August (9, 12 and 23) and explained the evolution of critical quantities (namely wind, pressure and humidity) during those periods. Results show the existence of meteorological scenarios suitable for Tropospheric Ozone production and the persistence of re-circulation phenomena (namely stable sea breezes) with consequent pollution low depletion and accumulation. Peculiar coastal phenomena have also been highlighted, such as breeze fronts capable of significant increment of both ozone and precursor concentrations.