The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Knut Stamnes - One of the best experts on this subject based on the ideXlab platform.
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AccuRT: A versatile tool for radiative transfer simulations in the coupled Atmosphere-Ocean System
2017Co-Authors: Børge Hamre, Knut Stamnes, Snorre Stamnes, Jakob J. StamnesAbstract:Reliable, accurate, and efficient modeling of the transport of electromagnetic radiation in turbid media has important applications in the study of the Earth’s climate by remote sensing. For example, such modeling is needed to develop forward-inverse methods used to quantify types and concentrations of aerosol and cloud particles in the atmosphere, the dissolved organic and particulate biogeochemical matter in lakes, rivers, coastal, and open-ocean waters. It is also needed to simulate the performance of remote sensing detectors deployed on aircraft, balloons, and satellites as well as radiometric detectors deployed on buoys, gliders and other aquatic observing Systems. Accurate radiative transfer modeling is also required to compute irradiances and scalar irradiances that are used to compute warming/cooling and photolysis rates in the atmosphere and primary production and warming/cooling rates in the water column. AccuRT is a radiative transfer model for the coupled atmosphere-water System that is design...
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C-disort: A versatile tool for radiative transfer in coupled media like the Atmosphere-Ocean System
2013Co-Authors: Børge Hamre, Knut Stamnes, Snorre Stamnes, Jakob J. StamnesAbstract:We present a well-documented and well-tested numerical code c-disort that accurately models radiative transfer in the coupled Atmosphere-Ocean System, and provides researchers with a professional tool that is user-friendly, reliable, accurate, and efficient.
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Discrete ordinate and Monte Carlo simulations of radiative transfer in coupled Atmosphere-Ocean Systems
2013Co-Authors: Snorre Stamnes, Jakob J. Stamnes, Endre R. Sommersten, Jon Kåre Lotsberg, D. Cohen, Tomonori Tanikawa, Knut StamnesAbstract:We present comparisons between deterministic solutions of the vector radiative transfer (RT) equation based on the discrete ordinate (DISORT) method and probabilistic simulations based on the Monte Carlo (MC) method for an atmosphere comprised of either a size distribution of spherical aerosol particles with an average size of 0.3 μm or a size distribution of spherical cloud particles with an average size of 5 μm. Also, we discuss preliminary deterministic results for a coupled Atmosphere-Ocean System consisting of two turbid media separated by a plane interface across which the refractive index changes abruptly.
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Vector Discrete‐Ordinate Radiative Transfer in the Coupled Atmosphere‐Ocean System: CAO‐VDISORT
2009Co-Authors: Endre R. Sommersten, Knut Stamnes, Jon Kåre Lotsberg, Jakob J. StamnesAbstract:A computer program has been developed to compute the polarized radiation field in a plane‐parallel medium consisting of two adjacent slabs with different indices of refraction, like the coupled atmosphere‐ocean System. The vertical inhomogeneity of each of the two slabs is accounted for by dividing it into several horizontally homogeneous layers with different scattering and absorption properties. The program, based on vector radiative transfer theory and the discrete‐ordinate method, includes thermal emission, scattering, and absorption in the medium as well as bidirectional reflection and emission at the lower boundary. Possible radiation sources include polarized or unpolarized collimated incident radiation or isotropic illumination at the upper boundary, as well as internal thermal sources. Comparisons with results from Monte Carlo simulations show that this CAO‐VDISORT code provides accurate results for all four elements of the Stokes vector (I, Q, U, and V), and that it is orders of magnitude faster than Monte Carlo simulations.
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Analytical solution of radiative transfer in the coupled Atmosphere-Ocean System with a rough surface.
Applied optics, 2006Co-Authors: Zhonghai Jin, Knut Stamnes, Thomas P. Charlock, Ken Rutledge, Yingjian WangAbstract:Using the computationally efficient discrete-ordinate method, we present an analytical solution for radiative transfer in the coupled Atmosphere-Ocean System with a rough air-water interface. The theoretical formulations of the radiative transfer equation and solution are described. The effects of surface roughness on the radiation field in the atmosphere and ocean are studied and compared with satellite and surface measurements. The results show that ocean surface roughness has significant effects on the upwelling radiation in the atmosphere and the downwelling radiation in the ocean. As wind speed increases, the angular domain of sunglint broadens, the surface albedo decreases, and the transmission to the ocean increases. The downward radiance field in the upper ocean is highly anisotropic, but this anisotropy decreases rapidly as surface wind increases and as ocean depth increases. The effects of surface roughness on radiation also depend greatly on both wavelength and angle of incidence (i.e., solar elevation); these effects are significantly smaller throughout the spectrum at high Sun. The model-observation discrepancies may indicate that the Cox-Munk surface roughness model is not sufficient for high wind conditions.
Xinxin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Chebyshev collocation spectral method for vector radiative transfer equation and its applications in two-layered media
Journal of Quantitative Spectroscopy and Radiative Transfer, 2020Co-Authors: Cun-hai Wang, Yan-yan Feng, Kai Yue, Yao-hua Yang, Yong Zhang, Xinxin ZhangAbstract:Abstract The Chebyshev collocation spectral method (CCSM) is developed for solving the vector radiative transfer equation (VRTE) in participating media and then extended to polarized radiative transfer problems in two-layered media. The derivation of the CCSM discretization for the VRTE is presented and the numerical performance of the CCSM is investigated. The accuracy of the CCSM for solving the VRTE is first verified by comparing the CCSM solutions for the polarized radiative transfer in a plane-parallel medium with published results. Afterward, the CCSM is applied to polarized radiative transfer problems in inhomogeneous media, including two-layered media with different scattering characteristics and two-layered media with different refractive indices. Finally, taking both effects of different medium properties and reflective/refractive interface into account, we investigated the polarized radiative transfer in a realistic Atmosphere-Ocean System via the CCSM and discussed the distributions of the Stokes vector components. Results show that the CCSM is accurate and efficient for solving the VRTE and the distributions of Stokes vector for a realistic Atmosphere-Ocean System are presented in detail.
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Time-dependent polarized radiative transfer in an Atmosphere-Ocean System exposed to external illumination
Optics express, 2019Co-Authors: Cun-hai Wang, Yan-yan Feng, Xun Ben, Kai Yue, Xinxin ZhangAbstract:Time-dependent polarized radiative transfer in an Atmosphere-Ocean System exposed to external illumination is numerically investigated. The specular reflection and transmission effects based on the relative refractive index between the atmosphere and water are considered. A modified Monte Carlo (MMC) algorithm combined with time shift and superposition principle, which significantly improves the computational efficiency of the traditional Monte Carlo (TMC) method, is developed to simulate the time-dependent polarized radiative transfer process. The accuracy and computational superiority of the MMC for polarized radiative transfer in the Atmosphere-Ocean System are validated, and the time-resolved polarized radiative signals are discussed.
Tatsuya Yokota - One of the best experts on this subject based on the ideXlab platform.
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matrix formulations of radiative transfer including the polarization effect in a coupled atmosphere ocean System
Journal of Quantitative Spectroscopy & Radiative Transfer, 2010Co-Authors: Yoshifumi Ota, Teruyuki Nakajima, Akiko Higurashi, Tatsuya YokotaAbstract:Abstract A vector radiative transfer model has been developed for a coupled atmosphere–ocean System. The radiative transfer scheme is based on the discrete ordinate and matrix operator methods. The reflection/transmission matrices and source vectors are obtained for each atmospheric or oceanic layer through the discrete ordinate solution. The vertically inhomogeneous System is constructed using the matrix operator method, which combines the radiative interaction between the layers. This radiative transfer scheme is flexible for a vertically inhomogeneous System including the oceanic layers as well as the ocean surface. Compared with the benchmark results, the computational error attributable to the radiative transfer scheme has been less than 0.1% in the case of eight discrete ordinate directions. Furthermore, increasing the number of discrete ordinate directions has produced computations with higher accuracy. Based on our radiative transfer scheme, simulations of sun glint radiation have been presented for wavelengths of 670 nm and 1.6 μm. Results of simulations have shown reasonable characteristics of the sun glint radiation such as the strongly peaked, but slightly smoothed radiation by the rough ocean surface and depolarization through multiple scattering by the aerosol-loaded atmosphere. The radiative transfer scheme of this paper has been implemented to the numerical model named Pstar as one of the OpenCLASTR/STAR radiative transfer code Systems, which are widely applied to many radiative transfer problems, including the polarization effect.
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Matrix formulations of radiative transfer including the polarization effect in a coupled atmosphere–ocean System
Journal of Quantitative Spectroscopy and Radiative Transfer, 2010Co-Authors: Yoshifumi Ota, Teruyuki Nakajima, Akiko Higurashi, Tatsuya YokotaAbstract:Abstract A vector radiative transfer model has been developed for a coupled atmosphere–ocean System. The radiative transfer scheme is based on the discrete ordinate and matrix operator methods. The reflection/transmission matrices and source vectors are obtained for each atmospheric or oceanic layer through the discrete ordinate solution. The vertically inhomogeneous System is constructed using the matrix operator method, which combines the radiative interaction between the layers. This radiative transfer scheme is flexible for a vertically inhomogeneous System including the oceanic layers as well as the ocean surface. Compared with the benchmark results, the computational error attributable to the radiative transfer scheme has been less than 0.1% in the case of eight discrete ordinate directions. Furthermore, increasing the number of discrete ordinate directions has produced computations with higher accuracy. Based on our radiative transfer scheme, simulations of sun glint radiation have been presented for wavelengths of 670 nm and 1.6 μm. Results of simulations have shown reasonable characteristics of the sun glint radiation such as the strongly peaked, but slightly smoothed radiation by the rough ocean surface and depolarization through multiple scattering by the aerosol-loaded atmosphere. The radiative transfer scheme of this paper has been implemented to the numerical model named Pstar as one of the OpenCLASTR/STAR radiative transfer code Systems, which are widely applied to many radiative transfer problems, including the polarization effect.
Teruyuki Nakajima - One of the best experts on this subject based on the ideXlab platform.
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Effects of ocean particles on the upwelling radiance and polarized radiance in the Atmosphere-Ocean System
Advances in Atmospheric Sciences, 2015Co-Authors: Chong Shi, Teruyuki Nakajima, Yoshifumi Ota, Pucai Wang, Sai-chun Tan, Guangyu ShiAbstract:Based on a vector radiative transfer model of the Atmosphere-Ocean System, the influence of oceanic components on radiation processes, including polarization effects, was investigated in the wavelength region ranging from 0.380 to 0.865 μm. The components considered were phytoplankton, inorganic suspended material (sediment), and colored, dissolved organic matter. Due to their important roles in oceanic radiation processes, the sensitivity of the bidirectional reflectance to the rough ocean surface, represented by the wind velocity 10 m above the ocean surface, and aerosol, were taken into account. The results demonstrated that both radiance and polarized radiance just below the ocean surface were sensitive to the change of the concentrations of the considered components, while the dependence of polarized radiance on the observation geometry was more sensitive than radiance. Significant differences in the specular plane existed between the impacts of the phytoplankton and sediment on the degree of polarization just above the ocean surface at 670 nm. At the top of the atmosphere (TOA), polarization was relatively insensitive to changing concentrations of ocean particles at longer wavelengths. Furthermore, the radiance at the TOA in the solar plane was more sensitive to the aerosol optical thickness than wind velocity. In contrast, wind velocity strongly influenced the radiance at the TOA in the sun glint region, while the polarization degree showed less dependence in that region. Finally, a nonlinear optimal inversion method was proposed to simultaneously retrieve the aerosol and wind velocity using radiance measurement.
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The Eddington approximation calculation of radiation flux in the atmosphere–ocean System
Journal of Quantitative Spectroscopy and Radiative Transfer, 2015Co-Authors: Chong Shi, Teruyuki NakajimaAbstract:Abstract An analytical approximation method is presented to calculate the radiation flux in the atmosphere–ocean System using the Eddington approximation when the upwelling radiation from the ocean body is negligibly small. Numerical experiments were carried out to investigate the feasibility of the method in two cases: flat and rough ocean surfaces. The results show good consistency for the reflectivity at the top of atmosphere and transmissivity just above the ocean surface, in comparison with the exact values calculated by radiative transfer models in each case. Moreover, an obvious error might be introduced for the calculation of radiation flux at larger solar zenith angles when the roughness of the ocean surface is neglected.
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matrix formulations of radiative transfer including the polarization effect in a coupled atmosphere ocean System
Journal of Quantitative Spectroscopy & Radiative Transfer, 2010Co-Authors: Yoshifumi Ota, Teruyuki Nakajima, Akiko Higurashi, Tatsuya YokotaAbstract:Abstract A vector radiative transfer model has been developed for a coupled atmosphere–ocean System. The radiative transfer scheme is based on the discrete ordinate and matrix operator methods. The reflection/transmission matrices and source vectors are obtained for each atmospheric or oceanic layer through the discrete ordinate solution. The vertically inhomogeneous System is constructed using the matrix operator method, which combines the radiative interaction between the layers. This radiative transfer scheme is flexible for a vertically inhomogeneous System including the oceanic layers as well as the ocean surface. Compared with the benchmark results, the computational error attributable to the radiative transfer scheme has been less than 0.1% in the case of eight discrete ordinate directions. Furthermore, increasing the number of discrete ordinate directions has produced computations with higher accuracy. Based on our radiative transfer scheme, simulations of sun glint radiation have been presented for wavelengths of 670 nm and 1.6 μm. Results of simulations have shown reasonable characteristics of the sun glint radiation such as the strongly peaked, but slightly smoothed radiation by the rough ocean surface and depolarization through multiple scattering by the aerosol-loaded atmosphere. The radiative transfer scheme of this paper has been implemented to the numerical model named Pstar as one of the OpenCLASTR/STAR radiative transfer code Systems, which are widely applied to many radiative transfer problems, including the polarization effect.
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Matrix formulations of radiative transfer including the polarization effect in a coupled atmosphere–ocean System
Journal of Quantitative Spectroscopy and Radiative Transfer, 2010Co-Authors: Yoshifumi Ota, Teruyuki Nakajima, Akiko Higurashi, Tatsuya YokotaAbstract:Abstract A vector radiative transfer model has been developed for a coupled atmosphere–ocean System. The radiative transfer scheme is based on the discrete ordinate and matrix operator methods. The reflection/transmission matrices and source vectors are obtained for each atmospheric or oceanic layer through the discrete ordinate solution. The vertically inhomogeneous System is constructed using the matrix operator method, which combines the radiative interaction between the layers. This radiative transfer scheme is flexible for a vertically inhomogeneous System including the oceanic layers as well as the ocean surface. Compared with the benchmark results, the computational error attributable to the radiative transfer scheme has been less than 0.1% in the case of eight discrete ordinate directions. Furthermore, increasing the number of discrete ordinate directions has produced computations with higher accuracy. Based on our radiative transfer scheme, simulations of sun glint radiation have been presented for wavelengths of 670 nm and 1.6 μm. Results of simulations have shown reasonable characteristics of the sun glint radiation such as the strongly peaked, but slightly smoothed radiation by the rough ocean surface and depolarization through multiple scattering by the aerosol-loaded atmosphere. The radiative transfer scheme of this paper has been implemented to the numerical model named Pstar as one of the OpenCLASTR/STAR radiative transfer code Systems, which are widely applied to many radiative transfer problems, including the polarization effect.
Cun-hai Wang - One of the best experts on this subject based on the ideXlab platform.
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Chebyshev collocation spectral method for vector radiative transfer equation and its applications in two-layered media
Journal of Quantitative Spectroscopy and Radiative Transfer, 2020Co-Authors: Cun-hai Wang, Yan-yan Feng, Kai Yue, Yao-hua Yang, Yong Zhang, Xinxin ZhangAbstract:Abstract The Chebyshev collocation spectral method (CCSM) is developed for solving the vector radiative transfer equation (VRTE) in participating media and then extended to polarized radiative transfer problems in two-layered media. The derivation of the CCSM discretization for the VRTE is presented and the numerical performance of the CCSM is investigated. The accuracy of the CCSM for solving the VRTE is first verified by comparing the CCSM solutions for the polarized radiative transfer in a plane-parallel medium with published results. Afterward, the CCSM is applied to polarized radiative transfer problems in inhomogeneous media, including two-layered media with different scattering characteristics and two-layered media with different refractive indices. Finally, taking both effects of different medium properties and reflective/refractive interface into account, we investigated the polarized radiative transfer in a realistic Atmosphere-Ocean System via the CCSM and discussed the distributions of the Stokes vector components. Results show that the CCSM is accurate and efficient for solving the VRTE and the distributions of Stokes vector for a realistic Atmosphere-Ocean System are presented in detail.
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Time-dependent polarized radiative transfer in an Atmosphere-Ocean System exposed to external illumination
Optics express, 2019Co-Authors: Cun-hai Wang, Yan-yan Feng, Xun Ben, Kai Yue, Xinxin ZhangAbstract:Time-dependent polarized radiative transfer in an Atmosphere-Ocean System exposed to external illumination is numerically investigated. The specular reflection and transmission effects based on the relative refractive index between the atmosphere and water are considered. A modified Monte Carlo (MMC) algorithm combined with time shift and superposition principle, which significantly improves the computational efficiency of the traditional Monte Carlo (TMC) method, is developed to simulate the time-dependent polarized radiative transfer process. The accuracy and computational superiority of the MMC for polarized radiative transfer in the Atmosphere-Ocean System are validated, and the time-resolved polarized radiative signals are discussed.