POLLUTION EPISODES AT VENICE RELATED TO WEATHER TYPES - AN ANALYSIS FOR A BETTER PREDICTABILITY

In order to obtain a rational strategy for the control and management of emissions from the industrial area of Venice, determination of the air quality is made from different perspectives. A source-receptor oriented approach shows a remarkable scatter of data due to the complex source field and variability of atmospheric conditions at a coastal site. As many pollution episodes are initiated by local diffusion potentials induced by the interaction between topographic irregularities (i. e. Alpine chain and Adriatic Sea) and the mesoscale atmospheric circulation system, a correlation between pollution events and synoptic conditions is made. Two periods of two years each were considered, the former characterized by very frequent, moderate episodes, the latter by more rare but potentially more severe episodes, although the emission rate was reduced. Four different criteria (i. e. weather types as classified by the U. K. Meteorological Office, by Borghi and Giuliacci, and by Urbani, and the passage of fronts) are considered and compared in order to describe the synoptic conditions and to make a reasonable prediction of the local dynamic climatology. A risk index (RI) is computed for each weather type.