Abstract :
A complete characterization of O3 photochemistry from a regulatory point of view includes knowing the production rate for O3, the sensitivity of this rate to NOx and VOCs, and the effects of emission controls on O3 concentration. Observation-based analysis techniques have been developed to determine these quantities based on observed concentrations of O3 and other photochemical ingredients. The promise of these methods is that reliable predictions on O3 control measures will be forthcoming from easily made measurements. We review several techniques that have been used in recent field programs. Techniques are divided into two families according to whether predicted quantities pertain to the present state of an air parcel or to its history. The present time frame methods address the question of what is happening now, whereas the past time frame methods are used to determine how the air mass evolved to its present state. Present time frame methods are used to determine O3 production rates and sensitivities. In this category, we discuss the constrained steady state, photostationary state, and radical budget methods. Past time frame techniques are used to address questions on the dependence of O3 on precursor emissions. In this category, we discuss indicator species and the “observation-based model”.
