EVALUATION OF 14 HAZARDOUS GAS MODELS WITH AMMONIA AND HYDROGEN-FLUORIDE FIELD DATA

Fourteen hazardous gas models are evaluated using data from the Desert Tortoise ammonia (NH3) and Goldfish hydrogen fluoride (HF) field experiments, which involved horizontal releases of aerosol jets. Seven experiments are available for analysis, with data at three downwind monitoring arcs, at distances ranging from 100 m to about 3000 m. The models include eight publicly available models, (ADAM, AFTOX, ALOHA, Britter and McQuaid, DEGADIS, HEGADAS, OB/DG, and SLAB) and six proprietary models (CHARM, EAHAP, PHAST, SAFETI, TRACE, and WHAZAN). In addition, the methods of initializing the ALOHA, CHARM, DEGADIS, and HEGADAS models were modified to account for initial dilution in an aerosol jet and these revised predictions were included in the evaluation. About one-half of the models yield relatively good performance in their predictions of maximum concentrations on monitoring arcs, with relative mean biases of +/- 30% or less and root mean square error (rmse) values that are about 40% to 60% of the mean. It is interesting that the simple Britter and McQuaid model performs just as well as some of the more sophisticated models, indicating that the simple model has captured the essence of the plume thermodynamics. Because this data set is not large, no significant differences can be shown (at the 95% confidence level) among the better models. This analysis will be expanded in the future to include other field datasets (e.g., Thorney Island and Maplin Sands).