Mountain-valley flow observations with a boundary layer wind profiler

For over 4 years, a boundary layer wind profiler and surface anemometer have collected measurements in Juneau, Alaska's Lemon Creek Valley. Statistical analysis of the anemometer wind directions has revealed daytime up-valley flow, nocturnal down-valley flow, and also a daytime cross-valley flow, all of which vary with season. These flows are expected based on the daytime solar forcing and nighttime radiative cooling. The wind profiler, using advanced signal processing to function in a mountain (high-clutter) environment, extends these statistical observations through the boundary layer, revealing a return flow aloft. There are a limited number of observations of return flow in the literature, generally made using pibals. This paper will focus on the added value of wind profiler observations for mountain observations. Seasonal characteristics of the flow events will be presented, along with specific case examples.