On the vertical distribution of carbon monoxide and methane in the stratosphere

Abstract

The vertical distribution of the methane concentration in the stratosphere is related to its dissociation by two simultaneous daytime reactions with excited oxygen atoms O(1D) and with OH radicals and depends on the stratospheric eddy diffusion coefficient. Dissociation of CH4 in the lower stratosphere leads to the production of CO molecules while in the upper stratosphere thepphotodissociation of CO2 molecules is an additional process to the CO production. In the upper stratosphere (40±10 km) there is an equilibrium between the formation and destruction processes of carbon monoxide which leads to a minimum of its mixing ratio. There is an increase of the CO mixing ratio in the troposphere and mesosphere compared with that of the stratosphere. The vertical distribution of the CO mixing ratio is closely related to the eddy diffusion coefficient in the whole stratosphere but the absolute values of the hydroxyl radical concentration also determine the values of the CO mixing ratio.