Analysis of an anomalous case of high air pollution concentration in Turinafter a foehn event

A case of unusually high concentrations of some urban air pollutants (CO, N O, SO2) in Turin (Northwestern Italy) is presented. This episode occurred d uring the late afternoon of 7 November 1995. This day was characterized by a strong northern foehn event in the morning, which followed the passage of a cold front. The analysis has been carried out by means of data derived f rom the urban and suburban air quality monitoring networks, of meteorologic al data (wind velocity, temperature and relative humidity) from the same ne twork and from other networks in the region, and of the output of the numer ical model LAMBO (operatively used by the Regional Meteorological Service o f Emilia Romagna). The analysis of meteorological data appears to be in goo d correlation with the distribution of the air pollutant concentrations; in particular, the high concentrations observed in the late afternoon are due to a strong thin inversion layer near the ground, developing immediately a fter the sudden end of the foehn episode.