Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

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Multivolume work

Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [THP-4 MICROWAVE SENSING]

Document type:: Multivolume work

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Chapter

Title:: PERFORMANCES OF A C-BAND MICROWAVE SCATTEROMETER FOR MONOTORING SOIL SURFACE MOISTURE ON BARE SOIL. P. BERTUZZI, L. BRUCKLER, A. CHANZY, G. GUYOT, E. CHAPUIS

Document type:: Multivolume work

Structure type:: Chapter

PERFORMANCES OF A C-BAND MICROWAVE SCATTEROMETER FOR MONOTORING SOIL SURFACE MOISTURE ON BARE SOIL P. BERTUZZIl*), L. BRUCKLER«*), A. CFIANZY < * > , G. GUYOT<**>, E. CHAPUIS(***> (*) Station de Science du Sol, Institut National de la Recherche Agronomique (I. N. R. A.), Domaine Saint-Paul, BP 91, 84143 Montfavet Cedex FRANCE (**) Station de Bioclimatologie, Institut National de la Recherche Agronomique (I. N. R. A.), Domaine Saint-Paul, BP 91, 84143 Montfavet Cedex FRANCE (***) Centre National d’Etudes Spatiales (C.N.E.S.), 18 Avenue Edouard Bel in, 31055 Toulouse FRANCE ABSTRACT Microwave backscattering coefficients were measured on 0.1 ha bare fields (27.2% clay, 61.7% fine and coarse loam, 11.1% sand) using a 5.3 GFIz frequency. Gravimetric soil moisture content, dry bulk density, and soil surface roughness were recorded concurrently with microwave measurements. The effects of the microwave penetration depth, soil surface roughness, and spatial heterogeneity of soil moisture distribution on the calibration relationship between the backscattering coefficient and the volumetric water content were evaluated. Results showed that (1) accurate soil surface (0-5 cm) moisture content estimates could be derived from microwave measurements (standard deviation of 0.02 m 3 • rrr 3 ) , (2) microwave penetration depth and soil surface roughness effects were negligible, (3) When heterogeneous soil surface water contents were considered, mean backscattering measurements were related to the mean soil water content. Moreover, the physical optics model was tested. It was shown that it was able to describe the soil moisture dependence at 15 and 23 angles of incidence, if near surface volumetric water content (0-1 cm depth layer) was used to compute the soil dielectric permittivity. kEY WORDS ¡Remote sensing,Microwave,C Band,Soil moi sture,Bare soi 1 1 . INTRODUCTION Extensive studies have been performed by several researchers using active microwave remote sensing to test the capability of such equipment to measure the soil surface water content (Ulaby et al., 1978; Bradley and Ulaby, 1981; Le Toan et al.. 1981; Bernard et al., 1982; Jackson and O’Neil, 1985; Bruckler et al., 1988) and to monitor the water budget at a field or regional scale. An optimal sensor configuration to measure soil water content (C band, polarization HFI, angle of incidence between 7 and 17) has been established (Ulaby et al., 1978): it was shown that using this optimal combination of frequency, look angle, and polarization, the backscattering coefficient was correlated to soil volumetric water content (Dobson and Ulaby, 1981). This paper is an experimental and theoretical contribution for evaluating under various field conditions on bare soils, the effects of different soil properties (soil surface water content gradients, soil surface roughness, soil heterogeneity) on backscattering coefficient measurements: (1) First, in most studies on microwave measurements on bare soils, experimental relationships between soil moisture content and backscattering coefficient were provided by mean volumetric water contents measured from the soil surface to an arbitrary soil depth (generally 0-5 or 0-10 cm). In fact, soil moisture gradients are sometimes very high in the top thin soil layers, which makes it difficult to attribute a real physical sense to calculated moisture content means. (2) Microwave measurements are generally performed on more or less heterogeneous soil surfaces: Soil surface water contents vary in a wide range during evaporation phases from one location to another for example, and thus, the radar is "looking" at heterogeneous thin soil layers. 702

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