Field study of the effect of orographic features on planetary boundary layer models

A flight program to measure the influence of orographic features on turbulent momentum, heat, and moisture fluxes was carried out. Characteristic wake flow patterns were observed in laboratory studies. While the upper level winds (above 10,000 ft msl) blow from west to east (perpendicular to the mountain range), flow patterns similar to flow from a backward-facing step are observed. When the upper level winds blow at 301 and 312 deg from true north (slightly oblique to the mountain range), experimental evidence suggests flow patterns typical of a vortex shed from the mountain range similar to a leading edge vortex from a delta wing aircraft. The observed flow patterns are analyzed. It is concluded that wake flow very similar to those observed in laboratory facilities can occur due to winds over mountain ranges. Results of studies in the laboratory may shed considerable insight to atmospheric boundary layer winds obstructed by orographic features.