אסיף מאגר המחקר החקלאי

On the Diurnal soil water content dynamics during evaporation using dielectric methods

Year:

2010

Source of publication :

Authors :

Volume :

9

Co-Authors:

Assouline, S., Institute of Soil, Water and Environmental Sciences, ARO, The Volcani Center, Bet Dagan, Israel
Narkis, K., Institute of Soil, Water and Environmental Sciences, ARO, The Volcani Center, Bet Dagan, Israel
Tyler, S.W., Dep. of Geological Sciences and Engineering, Univ. of Nevada, Reno, NV, United States
Lunati, I., Institute of Geophysics, Univ. of Lausanne, Lausanne, Switzerland
Parlange, M.B., School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
Selker, J.S., Dep. of Biological and Ecological Engineering, Oregon State Univ, Corvallis, OR, United States

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Abstract:

On the Diurnal Soil Water Content Dynamics during Evaporation using Dielectric Methods The water content dynamics in the upper soil surface during evaporation is a key element in land-atmosphere exchanges. Previous experimental studies have suggested that the soil water content increases at the depth of 5 to 15 cm below the soil surface during evaporation, while the layer in the immediate vicinity of the soil surface is drying. In this study, the dynamics of water content profiles exposed to solar radiative forcing was monitored at a high temporal resolution using dielectric methods both in the presence and absence of evaporation. A 4-d comparison of reported moisture content in coarse sand in covered and uncovered buckets using a commercial dielectric-based probe (70 MHz ECH 2O-5TE, Decagon Devices, Pullman, WA) and the standard 1-GHz time domain reflectometry method. Both sensors reported a positive correlation between temperature and water content in the 5- to 10-cm depth, most pronounced in the morning during heating and in the afternoon during cooling. Such positive correlation might have a physical origin induced by evaporation at the surface and redistribution due to liquid water fluxes resulting from the temperature-gradient dynamics within the sand profile at those depths. Our experimental data suggest that the combined effect of surface evaporation and temperature-gradient dynamics should be considered to analyze experimental soil water profiles. Additional effects related to the frequency of operation and to protocols for temperature compensation of the dielectric sensors may also affect the probes' response during large temperature changes. © Soil Science Society of America. All rights reserved.

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