Sensitivity of ozone production rate to ozone precursors

The photochemical equations describing O-3 formation in the lower troposphe re contain 2 major sink terms for free radicals; combination reactions and reactions with NOx. Knowing the fraction of radicals removed by reactions w ith NOx, termed L-N/Q, allows one to predict the sensitivity of O-3 product ion to NO and VOCs. We derive an analytic formula that gives L-N/Q in terms of readily measured O-3 precursors and test this formula using constrained steady state calculations based on field observations gathered in Phoenix, Arizona. The formula quantifies well-known results regarding the effects o f dilution, oxidation, and the production of oxidants on the transition fro m VOC to NOx sensitive behavior as an air parcel is advected away from an u rban source.