TIME-SPACE MODEL OF SUMMER OZONE DISTRIBUTION AROUND RAVENNA

The time-space distribution of photochemical ozone during the summer a long the western coast of the upper Adriatic Sea is strongly influence d by small-scale transport phenomena, especially land and sea breezes (Giovanelli et al., 1985). When these events involve the movement of a ir masses rich in primary and secondary pollutants across one or more lines of physical discontinuities, such as that between land and sea o r across the inshore strip (flat, predominantly farmland) lying betwee n seaboard and city, they can determine irregular, varying ozone distr ibution patterns at ground level in areas only a few kilometers apart. An empirical model was developed to characterize these local differen ces in ozone distribution over the entire area. The method makes it po ssible to compare the data recorded at the various sites and times by ''standardizing'' parameters for meteorological and local-diffusion co nditions as well as for source emission values by processing the data from a series of measurements taken at several coastal sites, both ins hore and offshore, during the summers 1980-1985. The resulting space-t ime models show, despite the limited number of monitor stations, ''loc al'' differences in the processes of production, transport, and spread of photochemical ozone in the area studied. The final distribution of the mean daily evolution (MDE) of ozone throughout the greater Ravenn a area is reported and discussed.