| The thesis focuses on the global modeling of tropospheric oxidants and simulates the production and transport of ozone and related species on a global scale. A global tropospheric 3-D Chemical Transport Model (CTM) driven by objectively analyzed wind fields is used. The CTM includes several modules viz transport, chemistry, photochemistry, emission and deposition. Parameterizations of convective transport and rainout processes are also included. To evaluate the ability of the model to represent the "real" world the results for some key tropospheric species are compared with the observations. Model sensitivity to emissions was evaluated by examining specific species in the biomass burning and anthropogenic emissions. The model reproduces the long range transport of biomass burning effluents from the major source regions of the Southern-hemisphere. With the biomass burning sources doubled the zonally averaged CO increased by 27--33% and ozone increased by 6--10% over the tropics and northern mid-latitudes. The sensitivity study indicates the need for improved emissions. The model is also used to study the impact of current and future subsonic aircraft emissions on tropospheric ozone and other related species such as nitrogen compounds and hydroxyl radicals. Calculations indicate that significant increase in abundance of upper tropospheric NO x and related species occurs in the northern hemisphere as a result of subsonic aircraft operations. The increase in the zonally averaged NO x concentration due to the 2015 aircraft emissions is estimated by the model to be as high as 70--80% at mid-latitudes in the northern hemisphere. The model calculates the maximum increase in the ozone abundance to be 18% in summer and 7% in winter.;Many improvements/extensions in the area of boundary layer mixing, heterogeneous chemistry, better emissions inventory, inclusion of total cloud coverage, etc. could be made to the present study. However, the results obtained with the model for the various studies are consistent with the observations and other model results. This supports the fact that the model with its limitations could be used to study the response of the atmosphere to natural and man-made perturbations. |
