Comparison of Wind Monitoring Systems. Part I: In Situ Sensors

It has recently become clear through advances in both theoretical and experimental meteorology, that improvements in modeling the transport and dispersion of pollutants will require on-site measurements of the atmosphere. This requirement has in turn generated questions about 1) our ability to make such measurements both near the surface and through the first few hundred meters of the atmosphere and 2) the expected accuracy and precision of such measurements using current technology. To help answer these questions an experiment was conducted at the Boulder Atmospheric Observatory to assess the ability of in situ and remote sensors to measure the mean and turbulent properties of the lower atmosphere. Two categories of sensors were tested. One consisted of lightweight in situ sensors of types that have been frequently used in the recent past for boundary layer studies. The other category consisted of four commercially available Doppler sodars, with the capability to measure wind speed, wind direction, and vertical component of turbulence, at various heights above the ground. Part one of this two part study deals with comparisons of five in situ wind sensing systems with a three-axis sonic anemometer, all mounted on 10 m towers spaced approximately 5 m apart. Discussed in this paper are statistical measures of their accuracy, precision and spectral response to fluctuations in the wind.