Theoretical Study of Three Dimensional Slope and Valley Wind Systems.
Abstract
The meso-scale flow over and around a finite length of mountain ridge and typical mountain valley terrain is studied. The present study is different from earlier analytical lee wave studies in that the solution is truly three-dimensional for more realistic topography. A simple model is developed and is attacked by multiple-scaling approach. The solutions are not only valid for large distances in the downwind direction, but are also good for the near regions. The phase lines of the vertical velocity on a horizontal plane at a given height have shape of hyperbolas and are concave toward downwind slide in accord with observations. The wind component parallel to the mountain ridge is found to be diffluent on the windward slope side, continuing to be so after crossing over the ridge in the lowest layer, and to become confluent at some distance downwind from the ridge. The intensity of the lee wave over a valley relates to the separation between the two ridges and the stability. Just above the valley floor, wind parallel to valley axis is in the down valley direction and thus raises the height of the maximum down-valley wind much higher than that of maximum 'slope wind' above the valley sides during the night. The computation also shows the increase of its intensity and height of occurrence with down-valley distance. In the farther downwind direction of the lee, the maximum confluent flow along the ridge is found at a much lower level and is stronger. The intensity and the position of the maximum wind parallel to the valley or the mountain ridges is closely related to the downslope motion of the lee wave. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1979
- Accession Number
- ADA078659
Entities
People
- Lev N. Gutman
- Louis N. Howard
- Wen Tang