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.
Highlights
The wind velocity variance, which represents the turbulent kinetic energy (TKE), is an important parameter of the atmospheric surface layer (ASL) since it conditions many phenomena taking place in this layer, such as the diffusion of chemical and physical aerosols, energy transfer between the mean and the turbulent flows, heat and mass transfer, extreme wind force exercised on structures, etc.Despite the existence of long established relationships (Panofsky et al, 1977), the behaviour of the variance of the horizontal wind components in the ASL stills discussed, specially the definition of their pertinent scaling parameters
The wind data logged during the WELSONS experiment concern the bottom part of the ASL since the lowest anemometer is located at 0.25 m from the ground while the highest one is at 4 m
The WELSONS experiment somewhat marks off from the cases reported in Sect. 2, since it took place in the very vicinity of the ground
Summary
Despite the existence of long established relationships (Panofsky et al, 1977), the behaviour of the variance of the horizontal wind components in the ASL stills discussed, specially the definition of their pertinent scaling parameters In this very specific study, which concerns the very lower layer of the ASL, called the “eddy surface layer (ESL)” (see Hunt and Carlotti, 2001), one has to highly consider the definition of the pertinent parameters. In this regard, the present study will briefly present some of the literature models, of which some are empirical ones while others stem from well known theories. A logarithmic profile model will be proposed for the variation of the variance
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
