Comparisons of Transport and Dispersion Model Predictions of the URBAN 2000 Field Experiment

The tracer releases of the “URBAN 2000” urban tracer and meteorological field experiment conducted in Salt Lake City, Utah, in October 2000 provided a wealth of data for comparison with the predictions of transport and dispersion models. Comparisons of several sets of predictions created with the U.S. Defense Threat Reduction Agency's urban Hazard Prediction and Assessment Capability (HPAC) model are compared with the observations of the URBAN 2000 field study. This analysis focuses on paired-in-space-and-time comparisons of predictions and observations and uses conventional statistics as well as a previously described transport and dispersion model user-oriented measure of effectiveness. Four urban HPAC model configurations and five weather input options were examined, and, thus, 20 sets of URBAN 2000 predictions were created. Novel features of this analysis include 1) an inclusive data protocol that allowed for the use of 94% of the observed URBAN 2000 sulfur hexafluoride (SF6) 30-min average concentrations, 2) the application of the previously developed user-oriented measure of effectiveness (MOE) to urban predictions and observations, and 3) the use of nonparametric hypothesis test procedures to guide objectively the search for significant performance differences between urban HPAC model configurations through over 25 000 comparisons of metrics. Robust findings are reported that include the statistical discernment of general trends associated with urban HPAC predictive performance as well as the identification of differences in performance among various model configurations.