Modeling the dispersion of tracer plumes in the Colorado front range boundary layer during night- and day-time conditions

摘要

The 1991 ASCOT (Atmospheric Studies in Complex Terrain) field study in the vicinity of the Department of Energy's Rocky Flats Plant, Colorado, was conducted to study the local and regional circulations and their interactions with synoptic flows over the complex terrain of the Rocky Mountains Colorado Front range. The ASCOT study focused on nocturnal flows from canyons and off slopes along the Front Range and their effect on transport and diffusion in the area. The study was combined with the Rocky Flats Winter validation Study (WVS) which had similar objectives but included a number of transition- and day-time experiments. Tracer plumes were released as part of this combined field campaign over the period of February 3--19, 1991 from the Rocky Flats Plant. Twelve intensive experiments, centered around eleven-hour long surface releases of sulfur hexafluoride (SF(sub 6)) tracer material, were conducted by teams of personnel from a number of national laboratories, government agencies and private contractors. The concentration patterns resulting from the transport and turbulent diffusion of the SF(sub 6) traces plumes within the atmospheric boundary layer during two night-time, one morning transition, and one day-time period were simulated for this paper. The model used for these simulations was the Lawrence Livermore National Laboratory (LLNL) three-dimensional, diagnostic MATHEW/ADPIC atmospheric dispersion model for complex terrain and flow conditions. The following will describe the model, the selected experiments, and the results of the comparison of predicted with observed tracer concentrations.