SEASONAL AND SPATIAL VARIABILITY OF OZONE INFERRED FROM GLOBAL CHEMISTRY TRANSPORT MODEL SIMULATIONS OVER INDIA

Abstract. In the present study, 3-D chemical transport model, MOZART-4 (Model for Ozone and Related chemical Tracers-Version-4) has been used to study the seasonal and spatial distribution of surface ozone (O₃) over India. To illustrate the capabilities of model, the simulations are compared with the ground-based observations. The model reproduces the principal features present in ground-based observations. However, model is unable to simulate very low concentration of O₃ during monsoon months. The model simulations are used to quantify the contribution of background ozone and Indian anthropogenic emissions to the variability of surface O₃. The spatial distribution of total O₃ (TO) shows maximum over Indo-Gangetic plains (IGP) and Eastern India while minimum over southern Indian region. The seasonal cycle of TO vary from 34.2 ± 7.6 to 51.9 ± 4.9 ppbv over the Indian landmass region due to changes in its topography and ozone lifetime. Annual mean total background O₃ (TBO) over India shows highest during spring (29.3 ± 5.0 ppbv) and lowest during monsoon (19.6 ± 3.4 ppbv). Both Natural background O₃ (NBO) and pollution background O₃ (PBO) shows a minimum in summer which are essentially following the seasonal changes of total ozone. Significant variation of India pollution O₃ (IPO) is found over India and the spatial variation of IPO follows the spatial variation of TO as well as spatial variation of emission of ozone precursors.