Study of Relationship between Daily Maxima in Ozone and Temperature in an Urban Site in India

The relationship between surface-level observations of daily maxima in ozone (O_3max) volume mixing ratio and ambient air temperature (Tmax) has been studied at an urban site, i.e. Pune (18.4°N, 73.8°E), India during 2003-04. The mixing ratios of O_3max were found to be highest during winter to pre-monsoon period and lowest in the monsoon season. The dependence of O_3max levels on T_max has been quantified using the linear regression fit for the different seasons. However, except for the monsoon season, reasonably good correlations between O_3max and T_max were noticed. The correlation between daily O_3max concentration and minimum NO_x (NO_^xmin) concentration was also studied to assess the importance of photochemical mechanism mainly reduction in the loss due to titration. Overall, the strong dependencies of O_3max on Tmax and NO_^xmin signify the role of both meteorological and photochemical processes during most months of a year. The positive slopes of ΔO_3max/ΔT_max and ΔO_3max/ΔNO_xmin clearly indicate the role of significant production and accumulation of O₃ under high temperature and low NO_x conditions respectively, during winter and premonsoon seasons. The statistical analysis of O₃ in relation with the key meteorological and chemical parameters is important to understand the sensitivity of secondary pollutants on various controlling factors.