scholarly journals On the reflectance spectroscopy of snow

2018 ◽  
Author(s):  
Alexander Kokhanovsky ◽  
Maxim Lamare ◽  
Biagio Di Mauro ◽  
Ghislain Picard ◽  
Laurent Arnaud ◽  
...  
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Reflectance Spectroscopy ◽  
System Of Nonlinear Equations ◽  
Electromagnetic Spectrum ◽  
European Alps ◽  
Snow Surface ◽  
Snow Albedo ◽  
Observation Geometry ◽  
Reflectance Measurements

Abstract. We propose a system of analytical equations to retrieve snow grain size and absorption coefficient of pollutants from snow reflectance or snow albedo measurements in the visible and near-infrared regions of the electromagnetic spectrum. It is assumed that ice grains and impurities (e.g., dust, black and brown carbon) are externally mixed. The system of nonlinear equations is solved analytically in the assumption that impurities influence registered spectra in the visible and not at near-infrared (and vice versa for ice grains). The theory is validated using spectral reflectance measurements and albedo of clean and polluted snow at various locations (Antarctica Dome C, European Alps). The technique to derive the snow albedo (plane and spherical) from reflectance measurements at a fixed observation geometry is proposed. The technique also enables the simulation of hyperspectral snow reflectance measurements in the broad spectral range from ultraviolet to the near-infrared for a given snow surface in the case, if the actual measurements are performed at restricted number of wavelengths (2–4, depending on the type of snow and the measurements system).

scholarly journals On the reflectance spectroscopy of snow

2018 ◽  
Vol 12 (7) ◽  
pp. 2371-2382 ◽  
Author(s):  
Alexander Kokhanovsky ◽  
Maxim Lamare ◽  
Biagio Di Mauro ◽  
Ghislain Picard ◽  
Laurent Arnaud ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Near Infrared ◽  
Single Scattering ◽  
Close Packing ◽  
System Of Nonlinear Equations ◽  
Electromagnetic Spectrum ◽  
European Alps ◽  
Snow Layer ◽  
Snow Albedo ◽  
Reflectance Measurements

Abstract. We propose a system of analytical equations to retrieve snow grain size and absorption coefficient of pollutants from snow reflectance or snow albedo measurements in the visible and near-infrared regions of the electromagnetic spectrum, where snow single-scattering albedo is close to 1.0. It is assumed that ice grains and impurities (e.g., dust, black and brown carbon) are externally mixed, and that the snow layer is semi-infinite and vertically and horizontally homogeneous. The influence of close-packing effects on reflected light intensity are assumed to be small and ignored. The system of nonlinear equations is solved analytically under the assumption that impurities have the spectral absorption coefficient, which obey the Ångström power law, and the impurities influence the registered spectra only in the visible and not in the near infrared (and vice versa for ice grains). The theory is validated using spectral reflectance measurements and albedo of clean and polluted snow at various locations (Antarctica Dome C, European Alps). A technique to derive the snow albedo (plane and spherical) from reflectance measurements at a fixed observation geometry is proposed. The technique also enables the simulation of hyperspectral snow reflectance measurements in the broad spectral range from ultraviolet to the near infrared for a given snow surface if the actual measurements are performed at a restricted number of wavelengths (two to four, depending on the type of snow and the measurement system).

scholarly journals Modeling Snow Surface Spectral Reflectance in a Land Surface Model Targeting Satellite Remote Sensing Observations

2020 ◽  
Vol 12 (18) ◽  
pp. 3101
Author(s):  
Donghang Shao ◽  
Wenbo Xu ◽  
Hongyi Li ◽  
Jian Wang ◽  
Xiaohua Hao
Keyword(s):  
Remote Sensing ◽  
Land Surface ◽  
Spectral Reflectance ◽  
Satellite Remote Sensing ◽  
Land Surface Model ◽  
Integrated Model ◽  
Surface Model ◽  
Snow Surface ◽  
Snow Albedo ◽  
Surface Models

Snow surface spectral reflectance is very important in the Earth’s climate system. Traditional land surface models with parameterized schemes can simulate broadband snow surface albedo but cannot accurately simulate snow surface spectral reflectance with continuous and fine spectral wavebands, which constitute the major observations of current satellite sensors; consequently, there is an obvious gap between land surface model simulations and remote sensing observations. Here, we suggest a new integrated scheme that couples a radiative transfer model with a land surface model to simulate high spectral resolution snow surface reflectance information specifically targeting multisource satellite remote sensing observations. Our results indicate that the new integrated model can accurately simulate snow surface reflectance information over a large spatial scale and continuous time series. The integrated model extends the range of snow spectral reflectance simulation to the whole shortwave band and can predict snow spectral reflectance changes in the solar spectrum region based on meteorological element data. The kappa coefficients (K) of both the narrowband snow albedo targeting Moderate Resolution Imaging Spectroradiometer (MODIS) data simulated by the new integrated model and the retrieved snow albedo based on MODIS reflectance data are 0.5, and both exhibit good spatial consistency. Our proposed narrowband snow albedo simulation scheme targeting satellite remote sensing observations is consistent with remote sensing satellite observations in time series and can predict narrowband snow albedo even during periods of missing remote sensing observations. This new integrated model is a significant improvement over traditional land surface models for the direct spectral observations of satellite remote sensing. The proposed model could contribute to the effective combination of snow surface reflectance information from multisource remote sensing observations with land surface models.

Spectral reflectance characteristics of eucalypt foliage damaged by insects

2001 ◽  
Vol 49 (6) ◽  
pp. 687 ◽  
Author(s):  
C. Stone ◽  
L. Chisholm ◽  
N. Coops
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Leaf Age ◽  
Electromagnetic Spectrum ◽  
Similar Response ◽  
Leaf Ontogeny ◽  
Maximum Slope ◽  
Mature Leaves ◽  
Eucalypt Species ◽  
Red Coloration

Variables related to foliar damage, leaf morphology, spectral reflectance, chlorophyll fluorescence and chlorophyll content were measured from leaves sampled from mature eucalypts exhibiting symptoms of crown dieback associated with bell miner colonisation located in Olney State Forest, near Wyong, New South Wales. Insect-damaged mature leaves and healthy young expanding leaves of some species exhibited a conspicuous red coloration caused by the presence of anthocyanin pigmentation. For the mature leaves, the level of red coloration was significantly correlated with insect herbivory and leaf necrosis. Significant correlations were also found between the level of red pigmentation and the following four spectral features: maximum reflectance at the green peak (550 nm); the wavelength position and maximum slope of the red edge (690–740 nm) and the maximum reflectance at 750 nm in the near-infrared portion of the electromagnetic spectrum. While it has been shown that anthocyanin pigments are synthesised in some eucalypt species in response to certain abiotic stresses causing photoinhibition and activation of photoprotective mechanisms, this work proposes that biotic agents such as leaf damaging insects and fungal pathogens may induce a similar response in eucalypt foliage resulting in increased levels of anthocyanins. The potential of anthocyanin levels to be related to leaf ontogeny for some eucalypt species was also illustrated in the reflectance spectra. Thus, it is essential that leaf age be considered. This work demonstrates that the identification of a number of key features of leaf spectra can provide a basis for the development of a robust forest health indicator that may be obtained from airborne or spaceborne hyperspectral sensors.

Use of reflectance measurements to estimate early cereal biomass production on sandplain soils

1993 ◽  
Vol 33 (2) ◽  
pp. 179 ◽  
Author(s):  
GA Elliott ◽  
KL Regan
Keyword(s):  
Biomass Production ◽  
Spectral Reflectance ◽  
Near Infrared ◽  
Stem Elongation ◽  
Selection Criterion ◽  
Poor Correlation ◽  
Breeding Programs ◽  
Mid Infrared ◽  
Cereal Breeding ◽  
Reflectance Measurements

High early biomass production has been suggested as a useful selection criterion for improving cereal yields in mediterranean environments. Current methods for measuring biomass production in cereal plots involves destructive sampling which is not suitable for routine use by plant breeders where large numbers of samples are to be screened. The measurement of spectral reflectance using ground-based remote sensing techniques has the potential to provide a nondestructive estimate of plant biomass production. This field study investigated the relationship between spectral reflectance and early biomass production in barley and wheat and assessed the feasibility of using spectral reflectance techniques in cereal-breeding programs. Spectral reflectance measurements (0.40-2.5 �m wavelengths) were made before stem elongation for barley and wheat grown in separate experiments at Wongan Hills, Western Australia. Cereal biomass was closely associated with spectral reflectance in the visible (0.44-0.66 �m) and mid infrared (1.50-1.80 �m and 2.00-2.40 �m) regions, but not in the near infrared (0.71-1.10 �m). The poor correlation between reflectance in the near infrared region and biomass production was due to the low amounts of biomass present and the high reflectivity of the sandplain soils at these wavelengths. The close associations in the visible and mid infrared regions provides promise for use in estimation of cereal biomass, but further research is required to refine the technique for use in large scale breeding programs.

scholarly journals Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin

2011 ◽  
Vol 5 (1) ◽  
pp. 203-217 ◽  
Author(s):  
H. S. Negi ◽  
A. Kokhanovsky
Keyword(s):  
Grain Size ◽  
Radiative Transfer ◽  
Spectral Reflectance ◽  
Art Theory ◽  
Snow Albedo ◽  
Seasonal Snow ◽  
Grain Sizes ◽  
Effective Grain Size ◽  
Reflectance Measurements ◽  
Good Agreement

Abstract. In the present paper, spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART) theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% differences. Retrieved integrated albedo was found within ±6% difference with ground observed broadband albedo. The retrieved snow grain sizes using different models based on the ART theory were compared for various snow types and it was observed that the grain size model using two channel method (one in visible and another in NIR region) can work well for the Himalayan seasonal snow and it was found consistent with temporal changes in grain size. This method can work very well for clean, dry snow as in the upper Himalaya, but sometimes, due to the low reflectances (<20%) using wavelength 1.24 μm, the ART theory cannot be applied, which is common in lower and middle Himalayan old snow. This study is important for monitoring the Himalayan cryosphere using air-borne or space-borne sensors.

scholarly journals Temporal and spatial variations in spectral reflectance and characteristics of surface dust on Gulkana Glacier, Alaska Range

2009 ◽  
Vol 55 (192) ◽  
pp. 701-709 ◽  
Author(s):  
Nozomu Takeuchi
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Spatial Variations ◽  
Snow Surface ◽  
Glacier Surface ◽  
Alaska Range ◽  
Infrared Wavelength ◽  
Temporal And Spatial Variations ◽  
Ice Surface ◽  
Temporal And Spatial

AbstractSpectral reflectances in the visible to near-infrared wavelength range (350–1050 nm) were measured on the surface of Gulkana Glacier, Alaska Range, Alaska, USA, at six different elevations from May to September 2001. The measurements showed variable spectral reflectances on the glacier surface, and the spectra changed over time and elevation. The spectra in May were those of a typical wet snow surface: the reflectance ranged approximately from 0.4 to 0.8, and generally decreased as the wavelength increased. As snowmelt proceeded, the reflectance gradually fell, and specific absorptions appeared in the spectrum at wavelength ranges of 400–600 and 670–680 nm, corresponding to a red snow surface due to snow algal bloom. As the ice surface was exposed, the spectrum finally shifted to a lower (0.1–0.4) and flat reflectance curve, typical of an ice surface contaminated with dust. Analyses of the dust on the glacier surface showed that its quantity and characteristics changed spatially and seasonally and were correlated with spectral albedo. The results showed that the temporal and spatial variations in spectral reflectance on this glacier are due not only to physical properties of the glacier surface, but also to biogenic materials on the surface (e.g red-colored snow algal cells and cryoconite).

scholarly journals Soot on snow experiment: bidirectional reflectance factor measurements of contaminated snow

2015 ◽  
Vol 9 (3) ◽  
pp. 3075-3111 ◽  
Author(s):  
J. I. Peltoniemi ◽  
M. Gritsevich ◽  
T. Hakala ◽  
P. Dagsson-Waldhauserová ◽  
Ó. Arnalds ◽  
...  
Keyword(s):  
Spectral Reflectance ◽  
Snow Surface ◽  
Bidirectional Reflectance ◽  
Hydrophobic Properties ◽  
Remarkable Feature ◽  
Bidirectional Reflectance Factor ◽  
Reflectance Factor ◽  
Natural Snow ◽  
Reflectance Measurements

Abstract. In order to quantify the effects of absorbing contaminants on snow, a series of spectral reflectance measurements were conducted. Chimney soot, volcanic sand, and glaciogenic silt were deposited on a natural snow surface in a controlled way as a part of the Soot on Snow (SoS) campaign. The bidirectional reflectance factors of these soiled surfaces and untouched snow were measured using the Finnish Geodetic Institute's Field Goniospectropolariradiometer, FIGIFIGO. A remarkable feature is the fact that the absorbing contaminants on snow enhanced in our experiments the metamorphosis of snow under strong sunlight. Immediately after deposition, the contaminated snow surface appeared darker than the pure snow in all viewing directions, but the absorbing particles sank deep into the snow in minutes. The nadir measurement remained the darkest, but at larger zenith angles the surface of the contaminated snow changed back to almost as white as clean snow. Thus, for a ground observer the darkening caused by impurities can be completely invisible, overestimating the albedo, but a nadir observing satellite sees the darkest points, now underestimating the albedo. By a reciprocity argument, we predict, that at noon the albedo should be lower than in the morning or afternoon. When sunlight stimulates sinking more than melting, the albedo should be higher in the afternoon than in the morning, and vice versa when melting dominates. However, differences in the hydrophobic properties, porosity, clumping, or size of the impurities may cause different results than observed in these measurements.

scholarly journals Floral Radiometry: A Biophysical Basis to Characterize Landscapes

2016 ◽  
Author(s):  
R. Jaishanker ◽  
N.P. Sooraj ◽  
M. Somasekheran Pillai ◽  
K. Athira ◽  
Ammini Joseph ◽  
...  
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Flower Color ◽  
Electromagnetic Spectrum ◽  
Ecological Research ◽  
Near Infrared Reflectance ◽  
Early Results ◽  
Representative Species ◽  
Spectrum Characteristic ◽  
Angiosperm Species

AbstractThis paper presents early results on studies of floral spectral reflectance of angiosperms and introduces floral radiometry as an emergent dimension of ecological research in India. Floral spectral reflectance of 121 angiosperm species was measured using hand-held spectroradiometer. The authors describe spectral reflectance of seven representative species within 350-800 nanometer region of the electromagnetic spectrum. Characteristic absorption and reflection of flowers, in ultraviolet and visible regions of the spectrum is reported. Near infrared reflectance was consistently high for all species studied. Flower color is unique to a species and importance of understanding flower color from pollinator’s perspective is highlighted.

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