Characterization Of Snow Grain Size In The Near-infrared And Microwave Wavelengths
22 Mar 1993-pp 51-54
TL;DR: In this paper, the size distribution of the lognormal ice particle size distribution in the surface layer of the snowpack was analyzed using a stereologic analysis of snow samples, and the magnitude of the difference between the optical and microwave effective grain size was directly proportional to the width of the particle size distributions.
Abstract: Microwave backscatter and near-infrared reflectance are sensitive to snowpack gram size. Parameters describing the height and width of the lognormal ice particle size distribution are obtained through stereologic analysis of snow samples. The magnitude of the difference between the optical and microwave effective grain size is directly proportional to the width of the particle size distribution. The optically-effective grain size corresponds to the particle size distribution in the surface layer of the snowpack while the microwave grain size is an integrated value for the entire snowpack.
Citations
More filters
TL;DR: In this paper, a robust, accurate inversion technique was developed for estimating the grain size in a snowpack's surface layer from imaging spectrometer data. But the method is insensitive to instrument noise and does not require a topographic correction.
300 citations
Cites background from "Characterization Of Snow Grain Size..."
...Similarly, one can use the ratio of and geometric depth d. the third moment to the second moment of the lognormal Because flux extinction in snow is exponential (Bohren size distribution of snow grains (Nolin et al., 1993b)....
[...]
01 Jan 1972
TL;DR: The spectral reflectance of snow in the range of 0.60 to 2.50 microns wavelengths was studied in a cold laboratory using natural snow and simulated preparations of snow as discussed by the authors.
Abstract: The spectral reflectance of snow in the range of 0.60 to 2.50 microns wavelengths was studied in a cold laboratory using natural snow and simulated preparations of snow. A white barium sulfate powder was used as the standard for comparison. The high reflectance (usually nearly 100%) of fresh natural snow in visible wavelengths declines rapidly at wavelengths longer than the visible, as the spectral absorption coefficients of ice increase. Aging snow becomes only somewhat less reflective than fresh snow in the visible region and usually retains a reflectance greater than 80%. In the near infrared, aging snow tends to become considerably less reflective than fresh snow.
112 citations
TL;DR: In this paper, a model-derived characterization of the bidirectional reflectance distribution function provides the means for converting measured bidirectionally reflectance to directional-hemispherical albedo.
Abstract: With improvements in both instrumentation and algorithms, methods for mapping terrestrial snow cover using optical remote sensing data have progressed significantly over the past decade. Multispectral data can now be used to determine not only the presence or absence of snow but the fraction of snow cover in a pixel. Radiative transfer models have been used to quantify the nonlinear relationship between surface reflectance and grain size thereby providing the basis for mapping snow grain size from surface reflectance images. Model-derived characterization of the bidirectional reflectance distribution function provides the means for converting measured bidirectional reflectance to directional-hemispherical albedo. In recent work, this approach has allowed climatologists to examine the large scale seasonal variability of albedo on the Greenland ice sheet. This seasonal albedo variability results from increases in snow grain size and exposure of the underlying ice cap as the seasonal snow cover ablates away. With the current Mars Global Surveyor and future missions to Mars, it will soon be possible to apply some of these terrestrial mapping methods to learn more about Martian ice properties, extent, and variability. Distinct differences exist between Mars and Earth ice mapping conditions, including surface temperature, ice type, ice-mineral mixtures, and atmospheric properties, so a direct application of terrestrial snow and ice mapping methods may not be possible. However, expertise in mapping and interpreting terrestrial snow and ice will contribute to the inventory of techniques for mapping planetary ices. Furthermore, adaptation of terrestrial methods will provide a basis for comparison of terrestrial and planetary cryospheric components.
16 citations
TL;DR: In this article, an experimental device was placed on the concrete bunker of the Swiss Vallee de la Sionne avalanche dynamics test site and the captured particles have a geometric mean of 0.16 mm; the largest particles were 0.8 mm in size and the smallest particles 0.03 mm.
Abstract: Little quantitative information is available concerning the size of ice particles in the turbulent clouds of powder-snow avalanches. To quantify particle size distributions, we have developed an experimental device that collects particles in real-scale powder avalanches. The device was placed on the concrete bunker of the Swiss Vallee de la Sionne avalanche dynamics test site. On 31 January 2003, a large powder-snow avalanche struck the bunker and we were able to collect particle samples. The collected particles have been photographed and the pictures digitized. An image analysis tool allows us to determine an equivalent particle radius. The captured particles have a geometric mean of 0.16 mm; the largest particles were 0.8 mm in size and the smallest particles 0.03 mm.
10 citations
08 Aug 1994
TL;DR: In this paper, the spectral bidirectional reflectance-distribution function (BRDF) was used to estimate the spectral intensity of snow for a wide range of solar and viewing geometries.
Abstract: The angular distribution of reflected sunlight from snow is strongly anisotropic with most of the energy scattered in the forward direction. But, to obtain snow albedo from remote sensing data requires that we know the spectral bidirectional reflectance-distribution function (BRDF) as a function of snowpack physical properties such as snow depth, ice grain size, concentration of absorbing impurities and snowpack stratification. The authors establish the relationship between snow BRDF, snow physical properties, and solar/viewing geometries to improve estimates of surface albedo from remote sensing data. Using a discrete-ordinates radiative transfer model the authors have calculated the reflected spectral intensity of snow for a wide range of solar and viewing geometries. Corresponding snow reflectance measurements from Greenland and the Sierra Nevada, California, collected over a wide variety of snowpack conditions, show some agreement with the model results but the model appears to overestimate reflectance for solar zenith angles greater than 70 degrees. While snowpack physical properties are known to strongly affect the spectral reflectance of snow, the authors show how grain size, snowpack layering, and other physical properties also influence the angular reflectance from snow. >
9 citations
References
More filters
TL;DR: In this article, the spectral albedo of snow is calculated at any wavelength in the solar spectrum and which accounts for diffusely or directly incident radiation at any zenith angle.
Abstract: We present a method for calculating the spectral albedo of snow which can be used at any wavelength in the solar spectrum and which accounts for diffusely or directly incident radiation at any zenith angle. For deep snow, the model contains only one adjustable parameter, an effective grain size, which is close to observed grain sizes. A second parameter, the liquid-equivalent depth, is required only for relatively thin snow. In order for the model to make realistic predictions, it must account for the extreme anisotropy of scattering by snow particles. This is done by using the “delta-Eddington” approximation for multiple scattering, together with Mie theory for single scattering. The spectral albedo from 0.3 to 5 μm wavelength is examined as a function of the effective grain size, the solar zenith angle, the snowpack thickness, and the ratio of diffuse to direct solar incidence. The decrease in albedo due to snow aging can be mimicked by reasonable increases in grain size (50–100 μm for new snow...
1,487 citations
TL;DR: In this paper, an inversion technique and data collected by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was used to estimate the grain size for the near-surface snow layer.
165 citations
TL;DR: In this article, satellite observations of snow in the near-infrared wavelengths can be used to roughly estimate snow grain size, and it is possible to use measurements in the visible wavelengths to estimate snow water equivalence below some threshold value of around 100 mm.
Abstract: Satellite observations of snow in the near-infrared wavelengths can be used to roughly estimate snow grain size. When the grain size is large, it is possible to use measurements in the visible wavelengths to estimate snow water equivalence below some threshold value of around 100 mm. While sufficient data to fully evaluate these possibilities are not available, model calculations, selected satellite observations, and limited ground truth are in qualitative agreement. Complications arise because the effect of contamination by atmospheric aerosols is similar to that of finite depth, and because the near-infrared channel on the NOAA TIROS-N series satellites is not in the wavelength region where snow reflectance is most sensitive to grain size.
147 citations
01 Jan 1972
TL;DR: The spectral reflectance of snow in the range of 0.60 to 2.50 microns wavelengths was studied in a cold laboratory using natural snow and simulated preparations of snow as discussed by the authors.
Abstract: The spectral reflectance of snow in the range of 0.60 to 2.50 microns wavelengths was studied in a cold laboratory using natural snow and simulated preparations of snow. A white barium sulfate powder was used as the standard for comparison. The high reflectance (usually nearly 100%) of fresh natural snow in visible wavelengths declines rapidly at wavelengths longer than the visible, as the spectral absorption coefficients of ice increase. Aging snow becomes only somewhat less reflective than fresh snow in the visible region and usually retains a reflectance greater than 80%. In the near infrared, aging snow tends to become considerably less reflective than fresh snow.
112 citations
01 Jan 1975
TL;DR: The spectral reflectance of snow in the range of 0.60 to 2.50 microns wavelengths was studied in a cold laboratory using natural snow and simulated preparations of snow as discussed by the authors.
Abstract: The spectral reflectance of snow in the range of 0.60 to 2.50 microns wavelengths was studied in a cold laboratory using natural snow and simulated preparations of snow. A white barium sulfate powder was used as the standard for comparison. The high reflectance (usually nearly 100%) of fresh natural snow in visible wavelengths declines rapidly at wavelengths longer than the visible, as the spectral absorption coefficients of ice increase. Aging snow becomes only somewhat less reflective than fresh snow in the visible region and usually retains a reflectance greater than 80%. In the near infrared, aging snow tends to become considerably less reflective than fresh snow.
80 citations