Numerical Simulation of Terrestrial Radiation over a Snow Cover

P. Ducharme Saint-Eustache, Quebec, Canada

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A. Houdayer Laboratoire R.-J.-A.-Lévesque, Université de Montréal, Montreal, Quebec, Canada

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Y. Choquette Institut de Recherche d’Hydro-Québec (IREQ), Varennes, Quebec, Canada

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B. Kapfer Institut de Recherche d’Hydro-Québec (IREQ), Varennes, Quebec, Canada

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J. P. Martin Laboratoire R.-J.-A.-Lévesque, Université de Montréal, Montreal, Quebec, Canada

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Abstract

The intensity of terrestrial gamma radiation is a function of a number of parameters: emissivity and spatial distribution of the radioactive material in the soil, snow/water cover above ground, soil moisture content, type, and height above ground of the detector. Thus, the conversion of gamma measurements into reliable information must be based on a solid knowledge of the behavior of the gamma detector under different conditions. Such a detector, using a cylindrical NaI(Tl) crystal, was developed to remotely and automatically provide information on snow water equivalent (SWE) and soil moisture content (M). It became rapidly obvious that the behavior of the detector [gamma monitor (GMON)] over an infinite source could not be exactly reproduced in a laboratory. Therefore, a relatively simple model to simulate the behavior of GMON and to establish the relevant data analysis algorithms was conceived. This paper presents the basic assumptions for developing the model, the resulting algorithms, a comparison with field measurements, and some useful information on how GMON reacts to various field conditions.

Denotes Open Access content.

Deceased.

Corresponding author address: Y. Choquette, IREQ, 1800 Blvd. Lionel Boulet, Varennes QC J3X 1S1, Canada. E-mail: choquette.yves@ireq.ca

Abstract

The intensity of terrestrial gamma radiation is a function of a number of parameters: emissivity and spatial distribution of the radioactive material in the soil, snow/water cover above ground, soil moisture content, type, and height above ground of the detector. Thus, the conversion of gamma measurements into reliable information must be based on a solid knowledge of the behavior of the gamma detector under different conditions. Such a detector, using a cylindrical NaI(Tl) crystal, was developed to remotely and automatically provide information on snow water equivalent (SWE) and soil moisture content (M). It became rapidly obvious that the behavior of the detector [gamma monitor (GMON)] over an infinite source could not be exactly reproduced in a laboratory. Therefore, a relatively simple model to simulate the behavior of GMON and to establish the relevant data analysis algorithms was conceived. This paper presents the basic assumptions for developing the model, the resulting algorithms, a comparison with field measurements, and some useful information on how GMON reacts to various field conditions.

Denotes Open Access content.

Deceased.

Corresponding author address: Y. Choquette, IREQ, 1800 Blvd. Lionel Boulet, Varennes QC J3X 1S1, Canada. E-mail: choquette.yves@ireq.ca
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