Characteristics of Wind and Turbulence Just-Above and Within a Subalpine Forest in Complex Terrain

Winds at the the long-term Niwot Ridge Subalpine Forest AmeriFlux tower (US-NR1) have typically been measured at 3-4 levels between the primary flux-measurement level (21.5 m) and the ground. In order to enhance the vertical resolution of the wind profile, seven CSAT3 sonic anemometers were added to the US-NR1 tower in Fall of 2014 and operated for a full year. The US-NR1 site is located in complex mountainous terrain approximately 8 km east of the Continental Divide below Niwot Ridge, Colorado. The topography at the site has a slope angle that ranges from 4-7 degrees with much steeper terrain within several miles of the tower. The mixed-conifer subalpine forest surrounding the tower has a leaf-area index (LAI) of approximately 3.8-4.2. In our study we explore: (1) how stability affected the vertical profile of wind speed, wind direction, and turbulence at the site, (2) the variability in location and magnitude of the above-canopy drainage jet maximum, (3) the differences in wind and turbulence characteristics between winter and summer, and (4) the effect of sonic transducer flow distortion on the vertical profile of turbulence.