Application of a Mass-Consistent Wind Model to Chinook Windstorms.

摘要

This thesis examines the applicability of a simple objective analysis technique on a personal computer to determine the detailed distribution of surface winds during strong downslope windstorms. A three-dimensional, mass-consistent, diagnostic wind flow model applicable to complex terrain (COMPLEX) was modified to analyze surface wind fields for two severe chinook windstorms in southern Alberta. Realistic results were produced in the case study analyses where maximum winds followed the position of the 'hydrostatic wave' trough, with the highest model wind speeds produced when the wave trough was closest to the mountains. Problems caused by the assumed two-dimensional wave structure included unrealistic changes in wind direction at some boundary points where the model flow surfaces passed beneath the terrain surface. Similarly, the intersection of flow surfaces with the terrain occasionally caused wind speed maxima to occur between, rather than over, hilltops as normally observed. The most significant error was found at the base of the terrain slope where windspeeds were underestimated as the hydrostatic wave trough was moved away from the mountains. Recommended improvements include the use of a hydraulic jump-like flow field in place of the hydrostatic wave perturbation in the model flow surfaces, and a more realistic treatment of the neutral boundary layer. (jhd)