Friction-Velocity Estimates Using the Trace of a Scalar and the Mean Wind Speed
Friction-velocity estimates, surface-renewal theory, wind logarithmic law
A semi-empirical approach based on surface-renewal theory for estimating the friction velocity is tested for measurements taken in the inertial sublayer. For unstable cases, the input requirements are the mean wind speed and the high-frequency trace (10 or 20 Hz) of the air or sonic temperature. The method has been extended to traces of water vapour (H2O) and carbon dioxide (CO2) concentrations. For stable cases, the stability parameter must also be considered. The method’s performance, taking the direct friction velocity measured by sonic anemometry as a reference, was tested over a growing cotton field that included bare soil with some crop residues at the beginning of the season. In general, the proposed friction-velocity estimates are reliable. For unstable cases, the method shows the potential to outperform the wind logarithmic-law computation. Discarding cases with low wind speeds (e.g., < 0.3 m s−1 and mean wind shear < 1 Hz), the proposed approach may be recommended as an alternative method to estimating the friction velocity. There is the potential, based on the input requirements, that the proposed formulation may offer significant advantages in the estimation of the friction velocity in some marine environments.
Castellvi, F., Suvocarev, K., Reba, M. L., & Runkle, B. R. (2020). Friction-Velocity Estimates Using the Trace of a Scalar and the Mean Wind Speed. Biological and Agricultural Engineering Faculty Publications and Presentations. https://doi.org/https://doi.org/10.1007/s10546-020-00520-1