Statistical comparison of observed and CMAQ modeled daily sulfate levels

New statistical procedures to evaluate the Models-3/Community Multiscale Air Quality (CMAQ) using observed data are introduced. Certain space–time correlations are used to assess dynamic aspects of CMAQ and to compare the space–time structure of CMAQ to that of observations. Our analyses show that, overall, CMAQ matches the space–time correlation structure of observed sulfate concentrations well. Analyses on the space–time correlation of the difference of observations and CMAQ output show that CMAQ partially captures time lagged spatial variation of sulfate concentrations. Separable covariance functions are shown to provide a poor description of the observations.