Windprofile

Windprofile refers to the vertical variation of wind speed and, sometimes, direction with height in the lower atmosphere, typically within the planetary boundary layer. It is influenced by surface roughness, thermal stability, and obstacles such as terrain, vegetation, and built structures. Understanding the wind profile is essential for wind resource assessment, dispersion modeling, structural design, and the siting of wind turbines and other tall installations.

Several mathematical formulations describe wind profiles. The logarithmic wind profile, derived from surface layer theory, expresses wind speed as U(z) = (u*/k) ln(z/z0), where u* is the friction velocity, k is the von Karman constant (about 0.41), z is height, and z0 is roughness length. The power-law profile uses U(z) = Uref (z/zref)^α, with the exponent α depending on stability and roughness. In practice, site data and various standard models, including stability-adjusted profiles, are used to fit observed wind speeds.

Measurement and estimation methods include fixed meteorological towers with multiple anemometers, and remote-sensing devices such as LIDAR and SODAR, as well as outputs from numerical weather prediction models. These profiles support wind resource assessments, turbine siting, load estimation, and dispersion modeling. In wind energy, the wind profile influences the extrapolated wind speed at turbine hub heights and affects anticipated energy production.

Limitations arise from assumptions of horizontal homogeneity and steady-state conditions. Real-world profiles vary with atmospheric stability, terrain complexity, and diurnal cycles. Near large obstacles or complex topography, profiles can deviate from simple models, necessitating site-specific measurements and more advanced modeling to capture shear, wakes, and other effects.