Using Nacelle-Mounted Anemometer Measurements to Analyze a Complex Terrain Effect on Wind Flow Pattern

The effect of complex terrain on the local wind flow is investigated using data from nacelle-mounted anemometers across two 10 km transects during the second Wind Forecast Improvement Project (WFIP2). Terrain in the study area include the deep Columbia River Gorge to rolling hills, encompassing different scales. Variability in wind resource depends on synoptic scale meteorological events and interactions between the flow and the local terrain.

Instrumented wind turbines near the Wasco, OR research site were selected for analysis. Groups of instrumented turbines were established. Ten groups based on hub-height and longitudinal position, (for terrain similarity) along a west to east transect created a spatially separated, temporally similar data set across ~10 km in distance.

Analysis of nocturnal wind speeds, during westerly wind flow shows clear indication of a terrain effect on mean wind speed regardless of wind speed magnitude, season or level of power production. Additionally, this effect appears to dominate any wind farm wakes. If the terrain influence is properly quantified, it may be removed from the measurements to further reveal wake effects of wind farms.

Results from analysis of two transects, each representing unique terrain signatures will be discussed. Ideas and methods that may be used to overcome this terrain induced effect will be shared.