Specular Reflection

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Haimeng Zhao - One of the best experts on this subject based on the ideXlab platform.

  • contribution of leaf Specular Reflection to canopy reflectance under black soil case using stochastic radiative transfer model
    Agricultural and Forest Meteorology, 2018
    Co-Authors: Bin Yang, Yuri Knyazikhin, Haimeng Zhao
    Abstract:

    Abstract Numerous canopy radiative transfer models have been proposed based on the assumption of “ideal bi-Lambertian leaves” with the aim of simplifying the interactions between photons and vegetation canopies. This assumption may cause discrepancy between the simulated and measured canopy bidirectional reflectance factor (BRF). Few studies have been devoted to evaluate the impacts of such assumption on simulation of canopy BRF at a high-to-medium spatial resolution (∼30 m). This paper focuses on quantifying the contribution of leaf Specular Reflection on the estimation of canopy BRF under a black soil case using one of the most efficient radiative transfer models, the stochastic radiative transfer model. Analyses of field and satellite data collected over the boreal Hyytiala forest in Finland show that leaf Specular Reflection may lead to errors of up to 33.1% at 550 nm and 32.8% at 650 nm in terms of relative root mean square error. The results suggest that, in order to minimize these errors, leaf Specular Reflection should be accounted for in modeling BRF.

Bin Yang - One of the best experts on this subject based on the ideXlab platform.

  • contribution of leaf Specular Reflection to canopy reflectance under black soil case using stochastic radiative transfer model
    Agricultural and Forest Meteorology, 2018
    Co-Authors: Bin Yang, Yuri Knyazikhin, Haimeng Zhao
    Abstract:

    Abstract Numerous canopy radiative transfer models have been proposed based on the assumption of “ideal bi-Lambertian leaves” with the aim of simplifying the interactions between photons and vegetation canopies. This assumption may cause discrepancy between the simulated and measured canopy bidirectional reflectance factor (BRF). Few studies have been devoted to evaluate the impacts of such assumption on simulation of canopy BRF at a high-to-medium spatial resolution (∼30 m). This paper focuses on quantifying the contribution of leaf Specular Reflection on the estimation of canopy BRF under a black soil case using one of the most efficient radiative transfer models, the stochastic radiative transfer model. Analyses of field and satellite data collected over the boreal Hyytiala forest in Finland show that leaf Specular Reflection may lead to errors of up to 33.1% at 550 nm and 32.8% at 650 nm in terms of relative root mean square error. The results suggest that, in order to minimize these errors, leaf Specular Reflection should be accounted for in modeling BRF.

K H Baines - One of the best experts on this subject based on the ideXlab platform.

  • a transmission spectrum of titan s north polar atmosphere from a Specular Reflection of the sun
    The Astrophysical Journal, 2013
    Co-Authors: Jason W Barnes, R H Brown, Christophe Sotin, J M Soderblom, Roger N Clark, Mate Adamkovics, T Appere, Sebastien Rodriguez, Bonnie J Buratti, K H Baines
    Abstract:

    Cassini/VIMS T85 observations of a solar Specular Reflection off of Kivu Lacus (87.?4N 241.?1E) provide an empirical transmission spectrum of Titan's atmosphere. Because this observation was acquired from short range (33,000?km), its intensity makes it visible within the 2.0, 2.7, and 2.8 ?m atmospheric windows in addition to the 5 ?m window where all previous Specular Reflections have been seen. The resulting measurement of the total one-way normal atmospheric optical depth (corresponding to haze scattering plus haze and gas absorption) provides strong empirical constraints on radiative transfer models. Using those models, we find that the total haze column abundance in our observation is 20% higher than the Huygens equatorial value. Ours is the first measurement in the 2-5 ?m wavelength range that probes all the way to the surface in Titan's arctic, where the vast majority of surface liquids are located. The Specular technique complements other probes of atmospheric properties such as solar occultations and the direct measurements from Huygens. In breaking the degeneracy between surface and atmospheric absorptions, our measured optical depths will help to drive future calculations of deconvolved surface albedo spectra.

  • Specular Reflection on titan liquids in kraken mare
    Geophysical Research Letters, 2010
    Co-Authors: K Stephan, R H Brown, Randolph L Kirk, Jason W Barnes, Christophe Sotin, R Jaumann, J M Soderblom, C A Griffith, Laurence A Soderblom, K H Baines
    Abstract:

    [1] After more than 50 close flybys of Titan by the Cassini spacecraft, it has become evident that features similar in morphology to terrestrial lakes and seas exist in Titan's polar regions. As Titan progresses into northern spring, the much more numerous and larger lakes and seas in the north-polar region suggested by Cassini RADAR data, are becoming directly illuminated for the first time since the arrival of the Cassini spacecraft. This allows the Cassini optical instruments to search for Specular Reflections to provide further confirmation that liquids are present in these evident lakes. On July 8, 2009 Cassini VIMS detected a Specular Reflection in the north-polar region of Titan associated with Kraken Mare, one of Titan's large, presumed seas, indicating the lake's surface is smooth and free of scatterers with respect to the wavelength of 5 μm, where VIMS detected the Specular signal, strongly suggesting it is liquid.

Laurence Talini - One of the best experts on this subject based on the ideXlab platform.

  • probing thermal waves on the free surface of various media surface fluctuation Specular Reflection spectroscopy
    Review of Scientific Instruments, 2008
    Co-Authors: Astrid Tay, Caroline Thibierge, D Fournier, Christian Fretigny, Francois Lequeux, Cecile Monteux, Jeanpaul Roger, Laurence Talini
    Abstract:

    Thermal motion gives rise to fluctuations in free surfaces; measurement of the thermally excited waves on such surfaces provides information on the mechanical properties of the medium. We have developed an optical tool to probe the thermally excited waves on free surfaces: surface fluctuation Specular Reflection (SFSR) spectroscopy. It consists in measuring the fluctuations in the position of a laser beam that is Specularly reflected onto the free surface of a medium. The position of the reflected beam is sensitive to the roughness of the probed surface; the thermal waves are detected by subtracting the light intensities collected on the two quadrants of a photodiode, on which the beam is centered. We show how the measured signal is related to the medium properties. We also present measurements performed on Newtonian liquids as well as on a viscoelastic solid; we show that in all cases, there is a very good agreement between experimental and computed spectra. SFSR thus applies to a broad range of material...

  • probing thermal waves on the free surface of various media surface fluctuation Specular Reflection spectroscopy
    arXiv: Soft Condensed Matter, 2008
    Co-Authors: Astrid Tay, Caroline Thibierge, D Fournier, Christian Fretigny, Francois Lequeux, Cecile Monteux, Jeanpaul Roger, Laurence Talini
    Abstract:

    Thermal motion gives rise to fluctuations in free surfaces; the propagation of the thermally excited waves on such surfaces depends on the mechanical properties of the medium. Their measurement can therefore provide information on those properties. We have developed an optical tool to probe the thermally excited waves on free surfaces: Surface Fluctuation Specular Reflection (SFSR) spectroscopy. It consists in measuring the fluctuations in the position of a laser beam, which is Specularly reflected onto the free surface of a medium, and is therefore sensitive to the roughness of that surface. We show how the measured signal is related to the medium properties. We also present measurements performed on Newtonian liquids as well as on a viscoelastic solid; we show that, in all cases, there is a very good agreement between experimental and computed spectra. SFSR thus applies to a broad range of materials. It moreover offers a very good temporal resolution and should provide a useful tool for dynamical measurements on complex fluids.

Yuri Knyazikhin - One of the best experts on this subject based on the ideXlab platform.

  • contribution of leaf Specular Reflection to canopy reflectance under black soil case using stochastic radiative transfer model
    Agricultural and Forest Meteorology, 2018
    Co-Authors: Bin Yang, Yuri Knyazikhin, Haimeng Zhao
    Abstract:

    Abstract Numerous canopy radiative transfer models have been proposed based on the assumption of “ideal bi-Lambertian leaves” with the aim of simplifying the interactions between photons and vegetation canopies. This assumption may cause discrepancy between the simulated and measured canopy bidirectional reflectance factor (BRF). Few studies have been devoted to evaluate the impacts of such assumption on simulation of canopy BRF at a high-to-medium spatial resolution (∼30 m). This paper focuses on quantifying the contribution of leaf Specular Reflection on the estimation of canopy BRF under a black soil case using one of the most efficient radiative transfer models, the stochastic radiative transfer model. Analyses of field and satellite data collected over the boreal Hyytiala forest in Finland show that leaf Specular Reflection may lead to errors of up to 33.1% at 550 nm and 32.8% at 650 nm in terms of relative root mean square error. The results suggest that, in order to minimize these errors, leaf Specular Reflection should be accounted for in modeling BRF.