We have a two dimensional (2-D) photochemical transport model , which we run on the IBM RS6000 system at PRL. This has helped us to study many important scientific issues like stratospheric ozone depletion, atmospheric transport, budget and mechanism of ozone production in the troposphere.

To begin with, the model has been used to assist balloon observations from Hyderabad in an attempt to identify key processes in the lower atmosphere and to test the model. The model has been used to study the loading of ozone depleting substances in the stratosphere and the results show that despite phase out of these substances, the Antarctic ozone depletion will continue for some more years. There have been few measurements of vertical distribution of SF₆ especially in the tropics, restricting validation of vertical transport in 2D global models. To fill in this void, we have compared the 2D model simulated profiles of SF₆ with observations made by our group at PRL over a decade. Comparisons with UARS/HALOE CH4 data indicate presence of Quasi Biannual Oscillation (QBO). We also confirm that global SF₆ source emissions should be distributed on the model grid proportional to electrical power usage. The budget of nitrous oxide (N₂O) in the atmosphere has been under debate for some time now, with proposals for new atmospheric sources and sinks. Keeping this in mind, we have compared the data obtained from Hyderabad balloon flights with results from the 2D model which incorporates the standard photochemistry for N₂O. The extent of deviations in the comparison study were used to infer the possibility of a new source/sink, hitherto undiscovered. We have also used the 2D model to study the altitude and latitude variation of the contribution of the new sources and sinks to the N₂O mixing ratios.