Tropospheric ozone: Coupling transport and photochemistry

The budget of tropospheric ozone is reexamined in the light of lower observed nitrogen oxide densities and revised reaction rates. To estimate the relative importance of transport and photochemistry, model calculations are presented which determine one-dimensional vertical ozone profiles at mid-latitudes for equinoctial conditions. These calculations imply that both photochemistry and transport are important in controlling the abundance of tropospheric ozone. We estimate that photochemical processes produce about 0.6×1011 and destroy about 1.4×1011 tropospheric ozone molecules cm−2 s−1, while mixing processes transport about 1.4×1011 ozone molecules cm−2 s−1 from the stratosphere into the troposphere and ground level fluxes destroy about 0.6×1011 ozone molecules cm−2 s−1. The sensitivity of our model calculations to transport parameters, key rate coefficients, and nitrogen oxide densities are discussed.