This research continues a program of theoretical research focusing on studies of processes influencing the composition of both the stratosphere and troposphere. The objective is to enhance understanding of factors responsible for the rapid changes taking place in the composition of the atmosphere. Studies of the mid-latitude stratosphere using measurements from the shuttle-borne ATMOS experiment, and other data sources, to test and improve current photochemical models will be carried out. This work will also include the development of semi- empirical models relating chemical and meteorological tracers, allowing reconstruction of 3-dimensional tracer distributions in the stratosphere, with applications to analyses of data obtained in recent aircraft missions to the polar regions. Studies of the troposphere include development of a 2-dimensional model, calibrated using our 3-dimensional tracer model, to investigate factors responsible for present and past changes in the abundance of methane, carbon monoxide and the oxides of nitrogen. The 3- dimensional model will be applied to study seasonal deposition of nitrate to ice in Antarctica, and selected investigations of photochemical and cloud processes in the planetary boundary layer.
