Simulation of stable flows over Granite Mountain

Slope and valley flow interactions at Granite Mountain, Utah, were studied through a set of extensive field observations during the MATERHORN project. Here, we present high-resolution simulations of downslope flows on the east slope of Granite Mountain with both idealized and realistic model configurations. Simulations are performed using the Weather Research and Forecasting (WRF) model. The goal is to capture both the detailed nature of the downslope flows and their interaction with valley flows. The idealized simulations capture the topography at 50 m resolution and focus on understanding the development of the downslope flow as it progresses down the slope, including entrainment from above. At this resolution, the immersed boundary method (IBM) is used to represent the topography. The real case simulations are performed using a set of nested grids for a particular IOP and are compared to field data. The model results are found to be sensitive to soil moisture and land cover specification, but capture the overall evolution during the night. Of particular interest are interactions between the slope flow and cold pool in the eastern valley. During the early mornings of quiescent fall IOP campaigns, cold pool "sloshing” occurs, where cold air from the valley collides with the downslope flow, generating significant turbulence in the otherwise stable nighttime atmosphere.