9422323 Sillman In recent years, results from two-dimensional global simulations have demonstrated that gas-phase hydrocarbon chemistry and aqueous chemistry both have significant impacts in the troposphere, particularly with regard to the important tropospheric species ozone, NOx, and hydroxyl radical. A complete analysis of these photochemical impacts requires a three-dimensional simulation. Recently three-dimensional chemical tracer models (CTMs) have been applied to photochemically active tropospheric species, however, the application of CTMs has been limited by computational constraints associated with the calculation of photochemical production and loss. The PI has developed an innovative numerical approach to solving the equations of tropospheric chemistry. This method uses special properties of tropospheric odd hydroeen to obtain a convergent implicit solution to the equations of photochemical production and loss. By utilizing specific photochemical properties of the troposphere as part of the solution, the method is computationally very fast. In this project, the existing capabilities will be extended in two directions. First, techniques will be developed to include aqueous photochemistry as part of the numerical code. Second, an analysis of the cycle of tropospheric reactive nitrogen in three-dimensional global models with gas-and aqueous-phase chemistry will be completed. This analysis will lead to direct comparisons between simulated reactive nitrogen species and recent measurements associated with the North Atlantic Regional Experiment.
