Effects of boundary layer turbulence on mountain waves

Studies are conducted using a large-eddy simulation model with the aim of understanding how boundary layer turbulence interacts with the formation and propagation of mountain waves. Flow over a 500 m obstacle is considered with boundary layer formation controlled by surface roughness and heat flux. Cases with no-slip lower boundary conditions are presented as a control case representing typical mesoscale mountain wave predictions. Preliminary results indicate that surface fluxes have a significant impact on wave formation. With strong heating, mountain waves are much weaker because of the growth of the boundary layer and lowering of stability near the mountain. Surface roughness also has a strong impact on the dynamics of the flow, particularly for conditions favoring strong lee-side winds. Conditions with surface cooling are also examined and contrasted with daytime upslope flow cases.