The WELSONS experiment: overview and presentation of first results on the surface atmospheric boundary-layer in semiarid Spain

Abstract

Abstract. This study presents the preliminary results of the local energy budget and dynamic characteristics of the surface atmospheric boundary-layer (SBL) during the WELSONS (wind erosion and losses of soil nutrients in semiarid Spain) experiment. Some Mediterranean regions suer land degradation by wind erosion as a consequence of their particular soil and climate conditions and inappropriate agricultural practice. In Spain, where land degradation by water erosion is well known, the lack of ®eld studies to quantify soils losses by wind erosion resulted in the European Community organizing a scienti®c program for this speci®c issue. The European programme known as WELSONS was devoted to study the wind erosion process in central Aragon (NE Spain). This multidisciplinary experiment, which began in 1996 and ®nished in 1998, was carried out over an agricultural soil which was left fallow. Within the experimental ®eld, two plots were delimited where two tillage treatments were applied, a mould-board ploughing (or conventional tillage denoted CT) and chisel ploughing (reduced tillage denoted RT). This was to study on bare soil the in¯uence of tillage method on surface conditions, saltation¯ux, vertical dust¯ux, erosion rates, dynamics characteristics such as friction velocity, roughness length, etc., and energy budget. The partitioning of the available energy, resulting from the dynamics of the SBL, are quite dierent over the two plots because of their own peculiar soil and surface properties. The ®rst results show that the RT treatment seems to provide a wind erosion protection. Because of the long data recording time and particular phenomena (formation of a crust at the soil surface, very dry conditions, high wind speed for instance), these microclimatological data acquired during the WEL-SONS programmes may be helpful to test atmospheric boundary-layer models coupled with soil models.

Turbulent characteristics of a semiarid atmospheric surface layer from cup anemometers – effects of soil tillage treatment (Northern Spain)

“…For a complete description of the WELSONS experiment, with a detailed description of the site, one should refer to Frangi and Richard (2000). The climate of this Spanish region is strongly influenced by two winds, namely Cierzo and Borchono, which are bound to a specific orography.…”

“…2). In a former paper, Frangi and Richard (2000) have already presented some results regarding the dynamics of the atmospheric surface layer (ASL) and the energy budget. After determining the main ASL parameters (friction velocity, roughness length, temperature scale, MoninObukhov length scale, etc.…”

“…The main dynamic characteristics of the Atmospheric Surface Layer (ASL) measured over the experimental site (friction velocity, roughness length, etc. ), and energy budget, have been presented previously (Frangi and Richard, 2000). The current study is based on experimental measurements performed with cup anemometers located in the vicinity of the ground at 5 different levels (from 0.25 to 4 m) and sampled at 1 Hz.…”

A Method for Estimating the Aerodynamic Roughness Length with NDVI and BRDF Signatures Using Multi-Temporal Proba-V Data

“…In this study, we use least-square method to determine z 0m [46,47]. Equation (1) can be written as the following simplified form:…”

Aerodynamic roughness length related to non-aggregated tillage ridges

“…A fitting of the average measured wind velocities and air temperature, using the classical equations of the Monin-Obukhov (1954), allows one to determine the dynamical parameters u * , θ * and z 0 . We used the software procedure optimized by Frangi and Richard (2000). …”