Objective Reduction of the Space-Time Domain Dimensionality for Evaluating Model Performance

In the United States, photochemical air quality models are the principal tools used by governmental agencies to develop emission reduction strategies aimed at achieving National Ambient Air Quality Standards (NAAQS). Before they can be applied with confidence in a regulatory setting, models’ ability to simulate key features embedded in the air quality observations at an acceptable level must be assessed. With this concern in mind, the U.S. Environmental Protection Agency (EPA) has recently completed several runs of the Community Multiscale Air Quality model (CMAQ) and the Regional Modeling System for Aerosols and Deposition model (REMSAD) to simulate air quality over the contiguous United States during the year 2001 with a horizontal cell size of 36 km×36 km. The meteorological model MM5 and the emission processor SMOKE were used to generate the input fields necessary for CMAQ and REMSAD. See Hogrefe et al (2004a) and Eder and Yu (2004) for more information about model settings.