Analysis of Surface Ozone Variations near Geophysics Synoptic Station for the year 2002

In this survey, the surface ozone measurements and meteorological parameters in the vicinity of synoptic station of Geophysics Institute (Tehran University) have been analyzed for a period from Jan to Nov 2002. The hourly averaged pattern of surface ozone shows that the ozone concentration is high in the afternoon as expected as a result of photochemical processes in urban environment and it also varies by local advection due to the local orography. Comparison between wind intensity and the surface ozone shows that, during the day, the advection of polluted air by anabatic wind which blows towards the station increases its intensity. Also a smaller secondary peak in the summer afternoons is due to change in wind regime, from anabatic to Katabatic. This is particularly in summer months especially for June. The main peak in daily ozone concentration also becomes weaker in other seasons due to slowing down of the photochemical processes. The monthly averaged ozone shows that, the main ozone peak has occurred in March (typically 64.4 ppbv) and the second peak in August (typically 49.5 ppbv). The comparison of the monthly averaged of total ozone (measured by Dobson photo-spectrometer) with the surface ozone shows that the main cause of the large peak in March, is due to the increasing of the total ozone and the transport of ozone from stratosphere to troposphere while the main cause of second peak in August is photochemical processes.