A 3-D modelling study of the sources and sinks of atmospheric carbon monoxide

A global three-dimensional atmospheric tracer transport model is used to study the sources and sinks of atmospheric carbon monoxide (CO). Source functions are included for the release of CO from the oxidation of methane, technological sources, biomass burning, the oxidation of hydrocarbons and the oceans. The removal of CO from the atmosphere is assumed to be largely due to oxidation through reaction with hydroxyl radicals (OH) and removal by soils. To compute CO destruction, a parameterised OH field, calibrated to reproduce the loss of methyl chloroform, is employed. For the removal of CO by soils, a model is used which assumes that the flux of CO into soils is dependent on net primary productivity. To constrain the magnitude of the CO sources and sinks, atmospheric observations of CO are used. The deduced total CO source is 1855–2355 Tg. If present estimates of the release of CO from biomass burning and oxidation of hydorcarbons are correct then removal by soils could potentially be a substantial sink for CO.