scholarly journals Spectral measurements of surface hoar crystals

2017 ◽  
Vol 63 (239) ◽  
pp. 477-486 ◽  
Author(s):  
SIMON HORTON ◽  
BRUCE JAMIESON
Keyword(s):  
Potential Method ◽  
Spectral Measurements ◽  
Near Surface ◽  
Remote Sensors ◽  
Shaped Surface ◽  
Average Reflectance ◽  
Infrared Wavelengths ◽  
Buried Layers ◽  
Snow Microstructure ◽  
Faceted Particles

ABSTRACTSurface hoar crystals are common on the surface of mountain snow covers. Once buried, layers of large plate-shaped surface hoar crystals are prone to releasing dangerous snow-slab avalanches. Since snow microstructure influences the optical properties of snow, remote sensors could potentially detect the formation of surface hoar and other snow types associated with avalanche release. The spectral reflectance of 377 snow samples was measured with a field spectrometer between 750 and 2500 nm, including 161 samples of surface hoar. Morphological snow shapes associated with critical avalanche layers (surface hoar, near-surface faceted particles and depth hoar) had lower average reflectance factors than non-critical snow shapes at infrared wavelengths. Needle-shaped surface hoar was more reflective than plate-shaped surface hoar, but there were no significant differences between different sizes of surface hoar. Normalized difference indices calculated with reflectance from two wavelength bands is presented as a potential method to classify critical snow surfaces remotely, although melt-freeze crusts near the surface complicated the classification. Accordingly, further studying on the effect of melt-freeze crusts and quantification of the bidirectional reflective properties of critical snow types is needed.

scholarly journals Thermal remote sensing of ice-debris landforms using ASTER: an example from the Chilean Andes

2012 ◽  
Vol 6 (2) ◽  
pp. 367-382 ◽  
Author(s):  
A. Brenning ◽  
M. A. Peña ◽  
S. Long ◽  
A. Soliman
Keyword(s):  
Thermal Imaging ◽  
Land Surface ◽  
Ground Surface ◽  
Thermal Inertia ◽  
Thermal Conditions ◽  
Late Summer ◽  
Near Surface ◽  
Remote Sensors ◽  
Rock Glaciers

Abstract. Remote sensors face challenges in characterizing mountain permafrost and ground thermal conditions or mapping rock glaciers and debris-covered glaciers. We explore the potential of thermal imaging and in particular thermal inertia mapping in mountain cryospheric research, focusing on the relationships between ground surface temperatures and the presence of ice-debris landforms on one side and land surface temperature (LST) and apparent thermal inertia (ATI) on the other. In our case study we utilize ASTER daytime and nighttime imagery and in-situ measurements of near-surface ground temperature (NSGT) in the Mediterranean Andes during a snow-free and dry observation period in late summer. Spatial patterns of LST and NSGT were mostly consistent with each other both at daytime and at nighttime. Daytime LST over ice-debris landforms was decreased and ATI consequently increased compared to other debris surfaces under otherwise equal conditions, but NSGT showed contradictory results, which underlines the complexity and possible scale dependence of ATI in heterogeneous substrates with the presence of a thermal mismatch and a heat sink at depth. While our results demonstrate the utility of thermal imaging and ATI mapping in a mountain cryospheric context, further research is needed for a better interpretation of ATI patterns in complex thermophysical conditions.

scholarly journals CARACTERIZAÇÃO ESPECTRAL NA REFLECTÂNCIA DE Eucalyptus grandis

FLORESTA ◽  
2012 ◽  
Vol 42 (2) ◽  
pp. 285
Author(s):  
Emanuel Araújo Silva ◽  
Gabriel Paes Marangon ◽  
Luana Dessbesell ◽  
Weslley Wilker Morais ◽  
Diogo Belmonte Lippert ◽  
...  
Keyword(s):  
Spectral Response ◽  
Block Design ◽  
Eucalyptus Grandis ◽  
Visible Range ◽  
Spectral Measurements ◽  
Randomized Block Design ◽  
Significant Difference ◽  
Average Reflectance ◽  
Santa Maria ◽  
Spectral Location

 O objetivo do trabalho foi comparar níveis de reflectância das folhas de Eucalyptus grandis Hill ex Maiden através de medidas espectrais a partir da localização das mesmas em relação à árvore e aos pontos cardeais. O experimento foi conduzido na área experimental pertencente à FEPAGRO, localizada no município de Santa Maria-RS. O trabalho compreendeu a instalação de delineamento blocos ao acaso. Com a utilização de um espectrorradiômetro FieldSpec®3, foram obtidas as medidas de radiância refletida da face superior das folhas e posteriormente trabalhados no software R. Na Banda 1 (400 a 700 nm), notou-se um pico que está relacionado ao total de clorofila na folha dentro da faixa do visível. Observou-se que folhas na posição leste foram as que apresentaram maior reflectância, e as folhas que estavam ao sul e ao oeste apresentaram as menores. Para a Banda 2 (700 a 1000 nm), observou-se diferença estatística significativa apenas entre os valores médios das reflectâncias no par de posições leste-oeste, contrastando com a Banda 1, que obteve diferença significativa entre as reflectâncias médias de todos os pares. A resposta espectral das folhas revelou-se estatisticamente diferente, confirmando, assim, que há diferença espectral relacionada à localização das árvores e posições de coletas das folhas.Palavras-chave: Espectrorradiometria; sensoriamento remoto; curva de reflectância. AbstractSpectral reflectance characterization in Eucalyptus grandis. The objective was to compare levels of reflectance of leaves of Eucalyptus grandis Hill ex Maiden using spectral measurements from their location in relation to the tree and the cardinal points. The experiment was carried out in the experimental area belonging to FEPAGRO, located in Santa Maria-RS. The work included the installation of a randomized block design. With the use of a spectroradiometer FieldSpec ® 3, it was measured the radiance reflected from the upper surface of leaves for further work with the software R. In the first band (400 to 700 nm), it was realized that a peak is related to total chlorophyll within the visible range. It was observed that the leaves heading east presented the highest reflectance and the leaves at south and west had the lowest one. For the second band (700 to 1000 nm), we observed a statistically significant difference only between the average values of reflectance in the pair of east-west positions, contrasting with the band that got a significant difference between the average reflectance of all pairs. The spectral response of leaves proved to be statistically different; it confirms that there are differences related to the spectral location of trees and locations of collected leaves.Keywords: Spectroradiometry; remote sensing; reflectance curve. 

Towards predicting temporal changes of the spectral signature of snow in visible and near-infrared wavelengths

1993 ◽  
Vol 17 ◽  
pp. 143-148 ◽  
Author(s):  
Robert E. Davis ◽  
Anne W. Nolin ◽  
Rachel Jordan ◽  
Jeff Dozier
Keyword(s):  
Near Infrared ◽  
Volume Ratio ◽  
Spectral Signature ◽  
Inversion Method ◽  
Transfer Model ◽  
Grain Sizes ◽  
Equivalent Sphere ◽  
Infrared Wavelengths ◽  
Snow Model ◽  
Snow Microstructure

This study links two models, one that simulates changes in snow microstructure and one that recovers microstructure properties from measurements of snow reflectance. An energy and mass transfer model, SNTHERM.89, was used to calculate snow grain growth. Grain-sizes from the model and measurements of grain bond areas provided estimates of the surface-to-volume ratio of the bulk snow, which were transformed to geometrically-equivalent sphere sizes. An inversion technique based on a discrete-ordinate model of the directional reflectance recovered optically-equivalent sphere sizes from reflectance measurements at 1.075 μm. The predictions of equivalent sphere sizes from the snow model and the recovered optical sphere sizes from the inversion method were compared with stereological measurements from snow sections. The geometrically-equivalent and optically-equivalent grain-sizes showed good agreement with each other and with stereological measurements from snow a few days old. The predictions of the reflectance inversion method also compared favorably with geometrically-equivalent grain-sizes measured from a melt-freeze surface crust. This investigation showed the potential for fully coupling snow property simulations with models to predict the spectral reflectance of snow.

Towards predicting temporal changes of the spectral signature of snow in visible and near-infrared wavelengths

1993 ◽  
Vol 17 ◽  
pp. 143-148 ◽  
Author(s):  
Robert E. Davis ◽  
Anne W. Nolin ◽  
Rachel Jordan ◽  
Jeff Dozier
Keyword(s):  
Near Infrared ◽  
Volume Ratio ◽  
Spectral Signature ◽  
Inversion Method ◽  
Transfer Model ◽  
Grain Sizes ◽  
Equivalent Sphere ◽  
Infrared Wavelengths ◽  
Snow Model ◽  
Snow Microstructure

This study links two models, one that simulates changes in snow microstructure and one that recovers microstructure properties from measurements of snow reflectance. An energy and mass transfer model, SNTHERM.89, was used to calculate snow grain growth. Grain-sizes from the model and measurements of grain bond areas provided estimates of the surface-to-volume ratio of the bulk snow, which were transformed to geometrically-equivalent sphere sizes. An inversion technique based on a discrete-ordinate model of the directional reflectance recovered optically-equivalent sphere sizes from reflectance measurements at 1.075 μm. The predictions of equivalent sphere sizes from the snow model and the recovered optical sphere sizes from the inversion method were compared with stereological measurements from snow sections. The geometrically-equivalent and optically-equivalent grain-sizes showed good agreement with each other and with stereological measurements from snow a few days old. The predictions of the reflectance inversion method also compared favorably with geometrically-equivalent grain-sizes measured from a melt-freeze surface crust. This investigation showed the potential for fully coupling snow property simulations with models to predict the spectral reflectance of snow.

scholarly journals Thermal remote sensing of ice-debris landforms using ASTER

2011 ◽  
Vol 5 (5) ◽  
pp. 2895-2933 ◽  
Author(s):  
A. Brenning ◽  
M. A. Peña ◽  
S. Long ◽  
A. Soliman
Keyword(s):  
Thermal Imaging ◽  
Land Surface ◽  
Ground Surface ◽  
Thermal Inertia ◽  
Thermal Conditions ◽  
Late Summer ◽  
Near Surface ◽  
Remote Sensors ◽  
Rock Glaciers

Abstract. Remote sensors face challenges in characterizing mountain permafrost and ground thermal conditions or mapping rock glaciers and debris-covered glaciers. We explore the potentials of thermal imaging and in particular thermal inertia mapping in mountain cryospheric research, focusing on the relationships between ground surface temperatures and the presence of ice-debris landforms on one side and land surface temperature (LST) and apparent thermal inertia (ATI) on the other. In our case study we utilize ASTER daytime and nighttime imagery and in-situ measurements of near-surface ground temperature (NSGT) in the Mediterranean Andes during a snow-free and dry observation period in late summer. Spatial patterns of LST and NSGT were mostly consistent with each other both at daytime and at nighttime. Daytime LST over ice-debris landforms was decreased and ATI consequently increased compared to other debris surfaces under otherwise equal conditions, but NSGT showed contradictory results, which underlines the complexity and possible scale dependence of ATI in heterogeneous substrates with the presence of a thermal mismatch and a heat sink at depth. While our results demonstrate the utility of thermal imaging and ATI mapping in a mountain cryospheric context, further research is needed for a better interpretation of ATI patterns in complex thermophysical conditions

Investigation of the Process Capability of Water Cavitation Peening and Shot Peening Processing

2011 ◽  
Vol 69 ◽  
pp. 83-87
Author(s):  
Bing Han ◽  
Chao Deng ◽  
Dong Ying Ju
Keyword(s):  
Shot Peening ◽  
Process Capability ◽  
Potential Method ◽  
Spring Steel ◽  
Bubble Collapse ◽  
X Ray Diffraction ◽  
Near Surface ◽  
Treatment Changes ◽  
Surface Morphologies ◽  
The Impact

Water cavitation peening (WCP) with aeration is a recent potential method in the surface enhancement techniques. In this method, a ventilation nozzle is adopted to improve the process capability of WCP by increasing the impact pressure, which is induced by the bubble collapse on the surface of components in the similar way as conventional shot peening(SP). In this paper, the process capability of water cavitation peening and shot peening is investigated, The residual stresses in the near-surface and surface morphologies of spring steel SAE 1070 was characterized by X-ray diffraction (XRD), optical microscopy (OM). After peening treatment, changes in surface morphologies, as well as residual stress with the different peening duration were recorded. The obtained results indicate that the WCP processing had a better surface finish than SP processing.

scholarly journals SMALL-AMPLITUDE DISCONTINUOUS DISTURBANCES IN PLEISTOCENE DEPOSITS OF THE VOLYN-PODILSKA UPLAND

2021 ◽  
pp. 51-73
Author(s):  
Roman Hnatiuk
Keyword(s):  
Small Amplitude ◽  
Winter Season ◽  
Normal Faults ◽  
Reverse Fault ◽  
Near Surface ◽  
Groundwater Levels ◽  
Aeolian Deposits ◽  
Rupture Plane ◽  
Ice Wedge ◽  
Buried Layers

The paper presents the results of the study of the small-amplitude discon¬tinuous disturbances of the possibly cryogenic (thermokarst) origin. The dislocations were found in the outcrops of Middle and Upper Pleistocene sediments of the Volyn-Podilska Upland, accumulated in periglacial or sub-periglacial conditions. The distur¬bances are represented mostly by the micro-normal faults and also by sheared fractures and are very similar to tectonic (seismogenic) discontinuities. The tectonotypic fractures in the near-surface deposits of the Pleistocene terraces of Western Bug and Styr (five sections within Volhynian Upland, four of them – in the valley of Bug), as well as in the cover of the Late Pleistocene sediments on the slope of the valley of Dniester (Galician Prydnisterya) are subjected to consideration, analysis and interpretation. In the last location the ruptures are represented mostly by the dis¬turbances identified as sheared fractures. In all others there are small-amplitude normal faults. One reverse fault, timed to an ice-wedge cast, was also revealed. Typical micro-normal faults of all sections are steep and have a number of other common features, which testifies to the same or almost identical mechanism of their formation. These features, in particular, are as follows: 1) insignificant (usually up to 2–2.5 m) length in cross-section and small (several centimeters) amplitude of displacement along the rupture plane; 2) gradual attenuation of the fractures up and down the section. All micro-normal faults are confined to sediments (thicknesses) that are partially or completely composed of sand. The formation of the micro-normal faults and other examined ruptures can be ex¬plained by the uneven compaction and the gravitational subsidence of the rocks, and in the section on the slope of the Dniester valley – also by their displacement down along the slope. It is probable that these processes occurred due to: 1) the degradation of the permafrost; 2) the dehydration of the sand deposits during a significant decrease in the groundwater levels; 3) the melting of the buried layers and lenses of snow, which were accumulated during the winter season in the thickness of sandy the niveo-aeolian deposits. In the outcrops of this terrace, they occur no less frequently than the confidently identified ice wedge pseudomorphs. Key words: small-amplitude disturbances; microfaults; thermokarst; Volyn-Podilska Upland.

SURFACE AND NEAR SURFACE STRUCTURE OF Fe–Co LAYERS BY SCATTERING-INTERFERENCE OF PRIMARY ELECTRONS

1997 ◽  
Vol 04 (06) ◽  
pp. 1267-1271 ◽  
Author(s):  
G. C. GAZZADI ◽  
A. DI BONA ◽  
F. BORGATTI ◽  
A. ROTA ◽  
S. VALERI
Keyword(s):  
Structural Characterization ◽  
Electron Emission ◽  
Near Surface ◽  
A Value ◽  
Bcc Structure ◽  
Buried Layers ◽  
Bcc Phase ◽  
Primary Electrons ◽  
Beam Diffraction

We studied the Co/Fe bi- and multilayer growth on Fe single crystal using the primary-beam diffraction modulated electron emission (PDMEE) technique. This approach enables a chemical selected structural characterization of both surface and buried layers and interfaces to be performed. Co growth on the Fe(001) surface was studied in the 3–70 ML coverage range. The transition from the initial epitaxial bcc phase of the Co film to the stable hcp phase was found to occur rather abruptly at 25–30 ML coverage, a value larger than previously reported in the literature. Subsequent Fe deposition on the Co hcp film recovers the bcc structure in the sandwiched Co layer. However, removal of the Fe epilayer by mild sputtering results again in an hcp Co film.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

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