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

Abstract

The relationship between surface-level observations of daily maxima in ozone (O3max) 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 O3max were found to be highest during winter to pre-monsoon period and low- est in the monsoon season. The dependence of O3max levels on Tmax has been quantified using the linear re- gression fit for the different seasons. However, except for the monsoon season, reasonably good correlations between O3max and Tmax were noticed. The correlation between daily O3max concentration and minimum NOx (NOxmin) concentration was also studied to assess the importance of photochemical mechanism mainly re- duction in the loss due to titration. Overall, the strong dependencies of O3max on Tmax and NOxmin signify the role of both meteorological and photochemical proc- esses during most months of a year. The positive slopes of O3max/ΔTmax and O3max/NOxmin clearly indicate the role of significant production and accu- mulation of O3 under high temperature and low NOx conditions respectively, during winter and pre-monsoon seasons. The statistical analysis of O3 in rela- tion with the key meteorological and chemical pa- rameters is important to understand the sensitivity of secondary pollutants on various controlling factors.