Evaluating Uncertainties in Regional Photochemical Air Quality Modeling

This review evaluates analyses that are or may be performed to estimate
uncertainties associated with air quality modeling used in regulatory planning
to meet National Ambient Air Quality Standards for ozone. The sources of uncertainties
in photochemical air quality simulation models (PAQSMs) are described.
Regulatory requirements for evaluating PAQSM performance and uncertainty concerns
not addressed through standard performance evaluations are discussed. Available
techniques for evaluating uncertainties are presented. Experiences with analyses
conducted most commonly are reviewed, as are those that might be used in a cohesive
model uncertainty evaluation. The review concludes with a call for renewed
emphasis on applying current techniques complemented by heretofore sparsely used
diagnostic, corroborative, and alternative approaches and enhanced observational
databases.