Time-Space Model of Summer Ozone Distribution Around Ravenna

The time-space distribution of photochemical ozone during the summer along the western coast of the upper Adriatic Sea is strongly influenced by small-scale transport phenomena, especially land and sea breezes (Giovanelli et al., 1985). When these events involve the movement of air masses rich in primary and secondary pollutants across one or more lines of physical discontinuities, such as that between land and sea or across the inshore strip (flat, predominantly farmland) lying between seaboard and city, they can determine irregular, varying ozone distribution patterns at ground level in areas only a few kilometers apart. An empirical model was developed to characterize these local differences in ozone distribution over the entire area. The method makes it possible to compare the data recorded at the various sites and times by "standardizing" parameters for meteorological and local-diffusion conditions as well as for source emission values by processing the data from a series of measurements taken at several coastal sites, both inshore and offshore, during the summers 1980-1985. The resulting space-time models show, despite the limited number of monitor stations, "local" 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 Ravenna area is reported and discussed.