Abstract
A statistical analysis of the ground level ozone from ten monitoring sites of nine selected cities of the Mie Prefecture of Japan was done to investigate the diurnal, weekdays and weekends, seasonal, and annual patterns for the period of 1991-2001. Results showed that all the cities exceeded the standard limit (60 ppb) with frequency ranging from 0.74% to 15.91% and 2.31% to 32.84% respectively of all hourly and the peak hourly (12.00-18.00) observations. An upward trend in ozone exceedance was observed in all the sites while maximum exceedance occurred in Yokkaichi, Tsu and Toba. Short term diurnal analysis showed no distinct pattern. However, long term patterns shows that a peak level was observed at about 13.00-15.00 hours. Significant differences between the diurnal cycles in the different sites may be attributed to local weather, and potential for photochemical conditions. Weekdays and weekends pattern of ozone level in peak months showed significant differences in different stations for different months. Generally higher level of ozone was found on Friday in all stations. Diurnal distribution of both yearly and monthly averaged data showed distinct pattern with a peak period between 11.00 to 18.00 hrs and seasonal fluctuations with relatively higher level of ozone during April to September mainly attributed to potentiality of local photochemical production and favorable meteorological conditions. An upward trend in yearly averaged ozone distribution was observed in all the cities that ranged from 15.87% to 40.21% between 1991 and 2001. A stepwise multiple-linear regression analysis showed significant correlations between ozone and its precursors and meteorological parameters. The determined regression models for different stations could facilitate to explain the factors involved in ozone level productions.
