Moving Beyond Monin-Obukhov Similarity Theory in Modelling Wind-Speed Profiles in the Lower Atmospheric Boundary Layer under Stable Stratification

Date

2014

Authors

Optis, Michael
Monahan, Adam H.
Bosveld, Fred C.

Journal Title

Journal ISSN

Volume Title

Publisher

Boundary-Layer Meteorology

Abstract

Monin–Obukhov similarity theory (MOST) is commonly used to model the windspeed profile at altitudes relevant to wind-power production (e.g. 10–200 m). Though reasonably accurate for unstable to weakly stable stratification, this approach becomes less accurate under increasingly stable stratification, largely due to the constant-flux surface layer assumed by MOST becoming shallower than the altitude range of interest. Furthermore, above the surface layer, the Coriolis force has a considerable influence on the wind-speed profile (in particular in the formation of low-level jets) that cannot be modelled using similarity theory. Our goal is to compare the accuracy of alternative extrapolation models that are more physically appropriate above the surface layer. Using data from the 213-m Cabauwmeteorological tower in the Netherlands between July 2007 and June 2008, it is shown thatMOST is accurate only at low altitudes and low stability, and breaks down at high altitudes and high stability. Local similarity is generally more accurate than MOST across all altitudes and stabilities, though the model requires turbulent flux data at multiple altitudes that is generally impractical. In contrast, a two-layer MOST–Ekman model is found to be comparable to the other models at low stability ranges and considerably more accurate in the high stability range, while requiring only a measure of surface stability and the geostrophic wind.

Description

Keywords

Ekman layer, Monin-Obukhov similarity theory, Stable stratification, Wind power, Wind profiles

Citation

Optis, M., Monahan, A., & Bosveld, F. C. (2014). Moving Beyond Monin-Obukhov Similarity Theory in Modelling Wind-Speed Profiles in the Lower Atmospheric Boundary Layer under Stable Stratification. Boundary Layer Meteorology, 153, 497-514. https://doi.org/10.1007/s10546-014-9953-z.