Three perfluorocarbon tracer gases were released at 2.5-day or 5.0-day intervals from two sites in central North America and sampled for 24-hr periods at 77 surface sites. The source-receptor distances ranged from less than 30 km to 3,000 km. The data were used to evaluate the long-range transport and diffusion simulations of acid deposition models and to establish a range of uncertainty for various model genres. The performances of three single-layer Lagrangian, six multiple-layer Lagrangian, and two multiple-layer Eulerian models were assessed using quantifiable measures based on comparisons of ensemble mean concentrations and plume widths as well as trajectory errors expressed as a function of transport time. In general, the multiple-layer Lagrangian models performed best in simulating the transport of the tracers, while the Eulerian models performed best in simulating the ensemble concentration frequency distributions. After 0.5 day of transport, trajectory errors ranged from 100 km to 400 km; after 2.5 days, the errors ranged from 300 km to 800 km. Beyond 2.5 days, errors from four Lagrangian models plateaued, while errors for the other models continued to increase, peaking at nearly 1,100 km after 3.5 days.

Shipping list no.: 90-655-P. "June 1990." Includes bibliographical references (pages 96-99). "EPA/600/3-90/051." "Funded ... under U.S. Department of Commerce contract no. 50-EANR-8-00025"--Title page verso.