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 system to both inputs and system parameters. A fast, formal sensitivity analysis method was developed for application to multidimensional, chemically-active environmental models. The technique was then implemented in a three-dimensional air quality model and applied to the South Coast Air Basin (SoCAB) of California. Using direct derivatives of the equations governing the evolution of species concentrations, the local sensitivities to a variety of model parameters (e.g., rate constants, dry deposition velocities, wind speed) and inputs (e.g., initial concentrations, ground-level emissions, wind speed) are computed simultaneously. Since the equations governing sensitivity coefficients have a structure similar to that of the pollutant concentrations, the implementation using this technique is straightforward and computationally efficient.