Observations of slope and valley flow interactions during MATERHORN

The study of the complex interactions between thermally driven slope flows and meso-scale valley flows was one of the goals of the Mountain Terrain Atmospheric Modeling and Observations Program (MATERHORN) conducted at the Granite Mountain Atmospheric Science Testbed (GMAST), US Army Dugway Proving Ground (DPG), Utah. To capture these phenomena, a suite of remote sensors and in-situ instrumentation was used, which could identify and educe salient physical processes. In addition to meteorological towers, Doppler wind LiDARs deployed at three locations on the eastern slope of Granite Peak were particularly useful, capturing the temporal and spatial evolution of the slope and valley circulations and their interaction. During high pressure background condition evenings, LiDAR data shows the shallow drainage slope flow was periodically undercut by the much colder valley circulation forming a collision of the two flows, leading to intense turbulent regions, intrusions and instabilities. In addition to the field measurements, slope and valley flow interactions are the focus of an on-going laboratory study. The goal is to determine the nature of the interactions, determine if there are flow instabilities, examine the turbulence near the region of interaction, and develop a simple scaling in the flow destruction region.