Turbulent Structure of Stably Stratified Nocturnal Slope Flows.
Abstract
Turbulence characteristics of wind and temperature fields in drainage flows over a simple slope were studied. Data was collected on a simple, nearly two-dimensional mountain ridge with little vegetation. Anemometers, thermistors, and thermometers were used to collect mean and turbulent wind and temperature data 150 m below the ridgeline. Evidence for katabatically driven winds was found for a wide range of ambient conditions whenever a surface inversion was formed. When a velocity jet characteristic of good slope flows was present, the vertical profiles of turbulence were found to differ significantly from those over flat terrain, with the turbulent kinetic energy no longer a monotonically decreasing function of height. Richardson number profiles revealed a value well in excess of critical values in the region of the jet. The existence of an internal mixing layer, found by other investigators in deeper drainage flows, was not confirmed. Calculations of turbulent kinetic energy budgets showed a close balance between shear production and viscous dissipation, with buoyancy forces playing a relatively minor role. Above the jet, the contribution from the vertical heat flux was only a few percent of the shear production term and resulted from a near-calculation of the contributions from the heat flux normal to the sloping surface and flux parallel to the surface. In this region, the heat flux parallel to the slope was upslope, resulting in an energy production term, while below the jet it was downslope, resulting in an energy loss. Keywords: Complex terrain.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1985
- Accession Number
- ADA155845
Entities
People
- J. C. Doran
- T. W. Horst