Surface ozone variability over western Maharashtra, India.

We present the simultaneous field measurements of surface ozone (O(3)) made at the five different sites of western Maharashtra, India for the period between 2001 and 2005. Seasonal variation in O(3) shows a pronounced maximum concentration about 40-50 ppbv in the summer and winter season in the urban site and similar concentration of O(3) is also observed in the rural site despite less emission of precursor gases. The increase in O(3) concentration is observed in the sugar factory premises during sugarcane crushing period. Diurnal patterns in O(3) do not show daytime in situ photochemical buildup at high altitude mountain site. The higher O(3) concentration is observed in the morning hours near to the dam than at urban and rural sites. These variations in O(3) indicate that the local pollutants are major contributors to the O(3) concentrations at the urban and rural sites, while regional transport plays a role at high altitude mountains site. Model simulations using a Eulerian photochemical model have also been carried out with the available data. The comparison of model results with observation shows that a diurnal and seasonal pattern is in good agreement.