A temporal model of tropospheric carbon-hydrogen chemistry

The numerical simulation of the troposphere including a nitrogen-oxygen-carbon-hydrogen atmosphere has been accomplished for homogeneous time dependent static chemistry, employing 30 species and approximately 70 reactions, by using the Keneshea code. The objectives have included the obtaining of the effective homogeneous chemical lifetimes of each species to compare with transport and residence times, quantification of the rates of production of species associated with the carbon monoxide source-sink anomaly for comparison with heterogeneous anthropogenic introduction, and a validation of the simpler steady state models of the troposphere. Particular attention has been given to the Weinstock-Niki-Levy mechanism for the conversion of CH4 to CO via OH attack. Their conclusion that the decomposition of methane is potentially a much larger global source of CO than fossil fuel combustion is verified. Hydroxyl radical concentrations are sufficiently high to predict a CO chemical lifetime of 0.1 year, in general agreement with the carbon dating conclusions of Weinstock. Diurnal variations of the pertinent species concentrations are presented.