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Jos Lelieveld – 2002

December 13, 2002 @ 3:30 pm – 4:30 pm
Senate Chamber, N940, Ross Building, York University

Title: Oxidation Power of the Atmosphere.

Abstract: The lecture will address the stability of global atmospheric hydroxyl (OH) chemistry in view of anthropogenic changes. The atmospheric lifetime of reduced and partly oxidized natural and pollutant gases is controlled by their oxidation into soluble compounds, which are subsequently removed by deposition processes. The oxidation process is mostly initiated by OH radicals, formed from the photodissociation of ozone. Therefore, OH is the cleaning agent of the atmosphere. Global OH concentrations have been derived from longterm measurements of the tracer gas methyl chloroform. These measurements have furthermore been used to estimate global OH trends, indicating substantial interdecadal changes. If correct, this might imply that the atmospheric oxidation capacity is not stable against perturbations. It appears that the marine atmosphere has been OH depleted by growing anthropogenic emissions of methane and carbon monoxide, whereas in regions more strongly polluted by nitrogen oxides OH has increased. Future atmospheric composition changes will likely be largest in the tropics where the oxidation power is highest and OH chemistry is most sensitive to perturbations. Brochure

Updated on August 6th, 2014.