Infrared measurement of free-water content and grain size of snow

Timo Hyvärinen, Jorma Lammasniemi

Research output: Contribution to journalArticleScientificpeer-review

11 Citations (Scopus)

Abstract

A method has been developed to measure the free-water content and grain size of snow by use of near-infrared methods.
It requires no direct physical sampling and uses reflectances at three optimally selected wavelengths. The method is based on two basic phenomena: first, snow reflection as a multiple-scattering phenomenon is strongly dependent on the grain size and the spectral variations in the ice absorption coefficient, and second, owing to differences between the absorption coefficients of ice and water, the reflection spectrum of dry snow differs from that of wet snow.
Hemispherically integrated spectral reflectance has been measured in the range between 600 and 2000 nm for several types of snow including metamorphic states from newly fallen to melted-refrozen and densities from 0.10 to 0.45 g/cm3. The effect on reflectance of up to 20 vol % free water has been studied. The reflectance of snow has also been analyzed theoretically using an approximate solution of the radiative transfer equation.
The experiments and theoretical calculations show that the free-water content and average grain diameter can be derived from reflectance measurements made at 1030, 1260, and 1370 nm. From measurements made so far it is estimated that an accuracy of ± 1.5 vol % can be achieved in the measurement of the free-water content and of ± 0.2 mm can be achieved in the measurement of the average grain size.
Original languageEnglish
Pages (from-to)342-348
JournalOptical Engineering
Volume26
Issue number4
DOIs
Publication statusPublished - 1987
MoE publication typeA1 Journal article-refereed

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snow
Snow
Water content
moisture content
grain size
Infrared radiation
reflectance
Ice
absorptivity
ice
spectral reflectance
Reflectometers
Multiple scattering
Radiative transfer
radiative transfer
water
Water
sampling
Sampling
Wavelength

Cite this

Hyvärinen, Timo ; Lammasniemi, Jorma. / Infrared measurement of free-water content and grain size of snow. In: Optical Engineering. 1987 ; Vol. 26, No. 4. pp. 342-348.
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title = "Infrared measurement of free-water content and grain size of snow",
abstract = "A method has been developed to measure the free-water content and grain size of snow by use of near-infrared methods. It requires no direct physical sampling and uses reflectances at three optimally selected wavelengths. The method is based on two basic phenomena: first, snow reflection as a multiple-scattering phenomenon is strongly dependent on the grain size and the spectral variations in the ice absorption coefficient, and second, owing to differences between the absorption coefficients of ice and water, the reflection spectrum of dry snow differs from that of wet snow. Hemispherically integrated spectral reflectance has been measured in the range between 600 and 2000 nm for several types of snow including metamorphic states from newly fallen to melted-refrozen and densities from 0.10 to 0.45 g/cm3. The effect on reflectance of up to 20 vol {\%} free water has been studied. The reflectance of snow has also been analyzed theoretically using an approximate solution of the radiative transfer equation. The experiments and theoretical calculations show that the free-water content and average grain diameter can be derived from reflectance measurements made at 1030, 1260, and 1370 nm. From measurements made so far it is estimated that an accuracy of {\~A}‚{\^A}± 1.5 vol {\%} can be achieved in the measurement of the free-water content and of ± 0.2 mm can be achieved in the measurement of the average grain size.",
author = "Timo Hyv{\"a}rinen and Jorma Lammasniemi",
year = "1987",
doi = "10.1117/12.7974077",
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Infrared measurement of free-water content and grain size of snow. / Hyvärinen, Timo; Lammasniemi, Jorma.

In: Optical Engineering, Vol. 26, No. 4, 1987, p. 342-348.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Infrared measurement of free-water content and grain size of snow

AU - Hyvärinen, Timo

AU - Lammasniemi, Jorma

PY - 1987

Y1 - 1987

N2 - A method has been developed to measure the free-water content and grain size of snow by use of near-infrared methods. It requires no direct physical sampling and uses reflectances at three optimally selected wavelengths. The method is based on two basic phenomena: first, snow reflection as a multiple-scattering phenomenon is strongly dependent on the grain size and the spectral variations in the ice absorption coefficient, and second, owing to differences between the absorption coefficients of ice and water, the reflection spectrum of dry snow differs from that of wet snow. Hemispherically integrated spectral reflectance has been measured in the range between 600 and 2000 nm for several types of snow including metamorphic states from newly fallen to melted-refrozen and densities from 0.10 to 0.45 g/cm3. The effect on reflectance of up to 20 vol % free water has been studied. The reflectance of snow has also been analyzed theoretically using an approximate solution of the radiative transfer equation. The experiments and theoretical calculations show that the free-water content and average grain diameter can be derived from reflectance measurements made at 1030, 1260, and 1370 nm. From measurements made so far it is estimated that an accuracy of ± 1.5 vol % can be achieved in the measurement of the free-water content and of ± 0.2 mm can be achieved in the measurement of the average grain size.

AB - A method has been developed to measure the free-water content and grain size of snow by use of near-infrared methods. It requires no direct physical sampling and uses reflectances at three optimally selected wavelengths. The method is based on two basic phenomena: first, snow reflection as a multiple-scattering phenomenon is strongly dependent on the grain size and the spectral variations in the ice absorption coefficient, and second, owing to differences between the absorption coefficients of ice and water, the reflection spectrum of dry snow differs from that of wet snow. Hemispherically integrated spectral reflectance has been measured in the range between 600 and 2000 nm for several types of snow including metamorphic states from newly fallen to melted-refrozen and densities from 0.10 to 0.45 g/cm3. The effect on reflectance of up to 20 vol % free water has been studied. The reflectance of snow has also been analyzed theoretically using an approximate solution of the radiative transfer equation. The experiments and theoretical calculations show that the free-water content and average grain diameter can be derived from reflectance measurements made at 1030, 1260, and 1370 nm. From measurements made so far it is estimated that an accuracy of ± 1.5 vol % can be achieved in the measurement of the free-water content and of ± 0.2 mm can be achieved in the measurement of the average grain size.

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