Comparisons of a puff trajectory model with real time tracer measurements

A series of seven tracer experiments were conducted at the Idaho National Environmental and Engineering Laboratory (INEEL) in Southeastern Idaho during April and May of 1999. In connection with this study SF₆ was used to mark the plume in real time. Two vans equipped with real time analyzers were dispatched to measure concentrations of SF₆ at downwind distances of 10 to 50 kilometers. MDIFF, a puff trajectory model was used to predict plume positions in real time. A wind field produced by 30 meteorological stations located in the Upper Snake River Plain of Idaho drives the model. The model calculated plume locations and concentrations in 5-minute time steps. This paper describes the comparisons of 5-minute averaged model produced concentrations with 5-minute averaged concentrations as measured by the vans. During each 5-minute time period the vans were slowly traversing over unimproved roads. Therefor, for comparison purposes the vans were assumed to be at positions averaged over the time period.

Two types of plots are presented in the paper. They include time histories showing the concentration fluctuations as the plume passes by a specified location and isopleths of modeled 5-minute footprints on a map of the area. In each type of plot both the modeled and the measured concentrations are shown.