Comparison of a Doppler Sodar with Bivanes and Cup Anemometers

Abstract

A commercial Doppler sodar was operated near a 300-m tower instrumented with bivanes and cup anemometers. Sodar measurements of wind speed and direction and a turbulence variable (σw) were compared with tower measurements at 90, 180, and 300 m. A total of 2084 15-min periods of data were compared during one year. The bias and precision of the sodar data were calculated with respect to the bivanes and anemometers. It was found that, with the exception of the azimuth bias, the sodar measurements exhibited a somewhat greater bias and higher (worse) precision than found in previous studies. The azimuth bias of the sodar with respect to the bivanes was much less than reported in previous studies. Reasons for the differences between the sodar and the tower instruments are discussed. Inspection of tower and sodar data indicated that with experience the sodar data could be quality assured reasonably well without the need for direct comparison with a tower. The study underscores the value of manual data inspection at a new installation to assess the effects of the local environment on the data quality.