Effect of Numerical Tolerances in the ORCHID Model: Modeling Dimethyl Sulfide and Mercury in the Atmosphere

摘要

The ORganic CHemistry Integrated Dispersion Model (ORCHID) couples an atmospheric chemistry model with a meteorological transport and dispersion plume model. ORCHID uses the Livermore Solver of Ordinary Differential Equations (LSODE) as its numerical solver. In the solution of ordinary differential equations (ODEs), LSODE uses numerical tolerances. The tolerances affect computer run time, the relative accuracy of calculated species concentrations, and whether or not LSODE converges to a solution using this system of equations. It is of interest to understand how different settings of these tolerances affect the calculated results. Box models have been developed to investigate the effects of varying these tolerances on the predicted species concentrations of two different atmospheric oxidation processes. The mechanisms which have been studied are dimethyl sulfide and mercury.