Profile of the horizontal wind variance near the ground in near neutral flow – K-theory and the transport of the turbulent kinetic energy

Abstract

Abstract. This paper deals with the characteristics of the atmospheric turbulent flow in the vicinity of the ground, and particularly with the profile of the horizontal wind variance. The study is based on experimental measurements performed with fast cup anemometers located near the ground at 5 different levels (from 0.25 to 4 m) and sampled at 1 Hz. The experiment was carried over two agricultural plots with various tillage treatments in a fallow semiarid area (Central Aragon, Spain). The results of this study reveal that near the ground surface and under moderate wind, the horizontal wind variance logarithmically increases with height, in direct relationship with the friction velocity and the roughness length scale. A theoretical development has allowed us to link this behaviour to the modeling of the turbulent kinetic energy (TKE) transport through the eddy diffusivity. Thus, the study proposes a formulation of the similarity universal function of the horizontal wind variance. Besides, the formulation offers a new method for the determination of the friction velocity and the roughness length scale and can be used for the evaluation of the TKE transport rate.

Friction velocity estimation using a 2D sonic anemometer in coastal zones

“…Here the velocity vector was rotated in the mean wind direction (i.e. the cross-wind component = 0), thus I is related to the turbulent intensity (Pope, 2006;Stapleton et al, 1995;Yahaya et al, 2009). Notice that eq.…”

“…Even if the wind coming from the sea may present different behavior depending on the sea state (Charnock, 1955;Wu, 1980;Yahaya, 2009), the fit is excellent (r 2 >0.79). However, other locations not so close to the coast would be influenced by the terrain between the coast and the measurement site; even in S1, the distinction between wind from the sea and from land is not sharp for wind directions aligned (±10 o ) with the shoreline.…”