Aircraft measurements of wave momentum flux over the Colorado Rocky Mountains

Results are presented from a programme designed to measure the momentum flux associated with standing gravity waves over the central Rocky Mountains of North America. The purpose was to determine momentum losses from the westerlies as they cross a mountainous section of the northern hemisphere where wave drag is believed to be substantial. The data from one to three instrumented aircraft, operating on 20 flight days, mostly during January to March of 1973, are in reasonably good conformity with linear wave theory and also correlate well with surface measurements of downslope winds. Downward westerly momentum flux averaged 0.5 ‐ 1.0 dynes cm⁻² (0.05 ‐ 0.1 Pa). The mean westerly flow on the flight days was near the climatological mean for the period of the project, although the mean flow over this period as a whole was much weaker than the climatological mean.