FAST, DIRECT SENSITIVITY ANALYSIS OF MULTIDIMENSIONAL PHOTOCHEMICAL MODELS

Sensitivity analysis is a powerful tool for understanding the response of an environmental system (e.g., air quality) or model of that syste m to both inputs and system parameters. A fast, formal sensitivity ana lysis method was developed for application to multidimensional, chemic ally-active environmental models. The technique was then implemented i n a three-dimensional air quality model and applied to the South Coast Air Basin (SoCAB) of California. Using direct derivatives of the equa tions governing the evolution of species concentrations, the local sen sitivities to a variety of model parameters (e.g., rate constants, dry deposition velocities, wind speed) and inputs (e.g., initial concentr ations, ground-level emissions, wind speed) are computed simultaneousl y. Since the equations governing sensitivity coefficients have a struc ture similar to that of the pollutant concentrations, the implementati on using this technique is straightforward and computationally efficie nt.