Boundary layer evolution within a canyonland basin. Part II: Numerical simulations of nocturnal flows and heat budgets
- Pacific Northwest National Lab., Richland, WA (United States)
A mesoscale model is used to simulate the nocturnal evolution of the wind and temperature fields within a small, elliptical basin located in western Colorado that has a drainage area of about 84 km{sup 2}. Individual terms of the basin atmospheric heat budget are also calculated from the model results. The model is able to reproduce key features of the observed potential temperature profiles over the basin floor and winds exiting the basin through the narrow canyon that drains the basin. The strength of the sidewall drainage flow varies around the basin and is a function of the source area above the basin, the local topography, and the ambient winds. Flows on the basin floor are affected primarily by the drainage winds from the northern part of the basin. Evaluation of the individual terms of the atmospheric heat budget show that the forcing due to advection and turbulent diffusion is significantly larger above the sidewalls than over the basin floor; therefore, measurements made over the basin floor would not be representative of the basin as a whole. A high rate of atmospheric cooling occurs within the basin throughout the evening, although the strongest cooling occurs in the early evening hours. Sensitivity tests show that the thermal structure, circulations, and rate of cooling can be significantly affected by ambient wind direction and, to a lesser extent, vegetation coverage. 20 refs., 15 figs., 3 tabs.
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 484433
- Journal Information:
- Journal of Applied Meteorology, Vol. 35, Issue 12; Other Information: PBD: Dec 1996
- Country of Publication:
- United States
- Language:
- English
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