From 1996 to 1999, an European project called WELSONS was led to better understand the impacts of changes in climate and land-use on soil degradation by wind erosion for agricultural soils in a semiarid region of north-east Spain (Central Aragon). This paper presents the main results obtained from the measurement activities of the WELSONS project aimed to generate an original data base to study wind erosion processes. The first objective was to evaluate the effects of climate and anthropogenic processes on surface characteristics of agricultural soils. During the whole WELSONS experiment, a physical dynamics characterization of the soil surface and of the atmosphere near the ground were determined for each field plot studied. Results from the characterisation of soil surface shows that reduced tillage (RT) lower soil erodibility by wind compared to conventional tillage (CT).Soil crusting, which is a common feature of soils in the area, can also be considered as a protecting element against wind erosion. The second objective was to study the mobilisation processes of soil-particles into the saltation layer. Strong and erosive Cierzo winds occurred frequently in the area of the experimental field, but because a soil surface crust was present, only a limited supply of material was available for wind erosion. However, a measured saltation transport flux could be obtained for each sampled period from the measurement of the mass of saltating particles transported during each erosion event. The third objective was to assess the atmospheric emission of fine dust into the suspension layer. Significant vertical dust flux of PM20 was observed only in the CT plot because, as the erosion events are supply-limited, a lower amount of material lying on the crust was transported by the wind and sandblasted to provide suspended dust. Finally, the sandblasting efficiency calculated in the present experiment could be interpreted as the result of a higher binding energy for silt loam soil particles compared to sandy loam, loamy sand and sandy textured soils.

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[1] This article reports on a multiobjective approach which is carried out on the physically based Soil-Vegetation-Atmosphere Transfer (SVAT) model. This approach is designed for (1) analyzing the model sensitivity to its input parameters under various environmental conditions and (2) assessing input parameters through the combined assimilation of the surface water content and the thermal infrared brightness temperature. To reach these goals, a multiobjective calibration iterative procedure (MCIP) is applied on the Simple Soil Plant Atmosphere Transfer-Remote Sensing (SiSPAT-RS) model. This new multiobjective approach consists of performing successive contractions of the feasible parameter space with the multiobjective generalized sensitivity analysis algorithm. Results show that the MCIP is an original and pertinent approach both for improving model calibration (i.e., reducing the a posteriori preferential ranges) and for driving a detailed SVAT model using various calibration data. The usefulness of the water content of the upper 5 cm and the thermal infrared brightness temperature for retrieving quantitative information about the main input surface parameters is also underlined. This study opens perspectives in the combined assimilation of various multispectral remotely sensed observations, such as passive microwaves and thermal infrared signals.

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The properties of the soil-water medium are presented in the literature independent of its internal organization and operation. The objective of this study is to develop and test a conceptual model that used a continuously measured shrinkage curve (Se) to describe the functional organization of the soil-water medium. In this model, two functional porosities (micro and macro) are delineated and quantified by the Se. In addition, the equilibrium for four functional water pools is represented and parameterized by the Se. A set of eleven parameters was found necessary to model the seven phases of the se and to describe the corresponding soil hydrostructural changes. A method to accurately obtain the parameters of this model by a specific analysis of the continuously measured se is demonstrated. Examples of continuously measured and modeled SCS according to the pedostructure model (PS) are presented and discussed.

The stable isotopic concentration (18O and 2H) of water in phreatic aquifers in the Sahelo‐Sudanese zone of Africa is representative of the original mean rainfall contributing to ground water recharge. The isotopic decrease of 18O in the rainwater and groundwater (−0.084 ‰ 100 km−1) showed an east‐west gradient. This suggests a supply of water vapor transported by the zonal flows East African Jet, Tropical Easterly Jet, and Easterly Waves, thus increasing the contribution from the evaporating surfaces of the Indian Ocean in relation to that of the Guinean monsoon. The gradient also indicates the importance of atmospheric recycling of continental water through evapotranspiration. A model of conservation of the isotopic masses is presented which takes into account the return of continental vapor toward the rain‐giving clouds. The remaining fraction of water vapor during the east‐west transit between Djibouti and Dakar is thus determined by evapotranspiration.

This paper describes a sensor dedicated to measuring the vertical profile of the complex permittivity and the temperature of any medium in which sensor electrodes are inserted. Potential applications are the estimate of the humidity and salinity in a porous medium, such as a soil. It consists of vertically-stacked capacitors along two conductive parallel cylinders of 5 cm in diameter and at a 10-cm distance to scan a significant volume of the medium (∼1 L). It measures their admittances owing to a self-balanced impedance bridge operating at a frequency in the range of 1-20 MHz, possibly 30 MHz. Thanks to accurate design and electronic circuit theory-based modeling, the determination of the admittances takes into account all distortions due to lead and bridge electromagnetic effects inside the sensor when working at high frequencies. Calibration procedures and uncertainties are presented. The article also describes developments to make the present sensor autonomous on digital acquisition, basic data treatment and energy, as well as able to transfer stored data by a radio link. These steps in progress are prerequisites for a wireless network of sensors.