Atmospheric Dispersion in Mountain Valleys and Basins.
The primary goal of this research is to further characterize and understand dispersion in valley and basin atmospheres. A secondary, and related goal, is to identify and understand the dominant physical processes governing this dispersion. This has been accomplished through a review of the current literature, and analyses of recently collected data from two field experiments. This work should contribute to an improved understanding of material transport in the atmospheric boundary layer. It was found that dispersion in a freely draining valley (Brush Creek valley, CO) atmosphere is much greater than in an enclosed basin (Roanoke, VA) atmosphere primarily because of the greater wind speeds moving past the release point and the greater turbulence levels. The development of a cold air pool in the Roanoke basin is the dominant process governing nighttime dispersion in the basin, while the nighttime dispersion in the Brush Creek valley is dominated by turbulent diffusion and plume confinement between the valley sidewalls. The interaction between valley flows and above ridgetops flows is investigated. A "ventilation rate" of material transport between the valley and above ridgetop flows is determined. This is important in regional air pollution modeling and global climate modeling. A simple model of dispersion in valleys, applicable through a diurnal cycle, is proposed.
- Pub Date:
- Physics: Atmospheric Science