CHEMICAL-DYNAMIC MODELING OF THE ATMOSPHERE WITH EMPHASIS ON THE METHANE OXIDATION

A brief general discussion of coupled chemical dynamical model applied in atmospheric chemistry is given. The basic concepts of lagrangian versus eulerian models and the averaging along one or more directions in space in eulerian models are discussed. A model can be viewed as set of relations and assumptions based on physical laws used to interpret how the input data determine the composition of the atmosphere. An overview of the necessary input data for such models and how their uncertainties influence the output of the models is given. Finally some new results from our 2-D photochemical tracer/transport model for the troposphere are used as an example of how such models can be used. The methane oxidation system is studied, and a significant feedback (35% at present) between increased emissions and concentrations of methane is found. Several aspects of the altered chemical composition is discussed to explain the calculated feedback including a primary (total HO(x)-budget) and a secondary (NO(x)-induced) mechanism and changes in the OH/HO2 ratio within the HO(x)-reservoir.