Investigation of the Applicability of SODAR for Wind Resource Measurements in Complex and Inhomogeneous Terrain

Increasingly, SODAR (Sonic Detection And Ranging) systems are being used for wind measurements as an alternative to tower-mounted anemometry. SODARs uses acoustic signals to resolve u, v, and w wind velocity components at multiple heights. The accuracy of SODAR measurements are affected by underestimation of wind speeds due to volume sampling, spurious signals from ambient noise or reflected SODAR signals, the effects of precipitation on estimates of vertical wind speeds and, sometimes, sampling of different volumes for each velocity component. Typically missing or ambiguous data increases with height. This paper evaluates the applicability of SODAR for wind resource measurements in complex and inhomogeneous terrain. The evaluation is based on data collected at three Massachusetts sites: Mt. Tom, Thompson Island and Northfield Mountain. The terrain at Mt. Tom and at Northfield Mountain is complex. Thompson Island data are compared to nearby anemometry and the usefulness of the SODAR for evaluating wind shear in offshore sites is considered. SODAR data from Northfield Mountain, collected next to a tower with standard anemometry and at a nearby site, are compared to the anemometry data. Additional operational issues related to the use of SODAR for wind resource measurements are discussed.