New Approach for Radiative-Transfer Computations in Axisymmetric Scattering Hot Media

2001 ◽  
Vol 15 (3) ◽  
pp. 317-325 ◽  
Author(s):  
Pierre-Emmanuel Baudoux ◽  
Antoine Roblin ◽  
Patrick Chervet
Keyword(s):  
Radiative Transfer ◽  
New Approach ◽  
Axisymmetric Scattering

scholarly journals New Computational Geometry Methods Applied to Solve Complex Problems of Radiative Transfer

2020 ◽  
Author(s):  
Francisco Salguero-Andújar ◽  
Joseph Cabeza-Lainez
Keyword(s):  
Radiative Transfer ◽  
Computational Geometry ◽  
Solid Angle ◽  
Computer Time ◽  
Graphical Interface ◽  
New Approach ◽  
Thermal Exchange ◽  
Complex Problems ◽  
Geometrically Complex ◽  
Aided Design

Several problems of radiative transfer are yet unsolved because of the difficulties of the calculations involved in them, especially if the intervening shapes are geometrically complex. The main goal of our investigation in this domain is to convert the formulas that were previously derived, into a graphical interface based on the projected solid-angle principle. Such procedure is now feasible by virtue of several widely diffused programs for Algorithms Aided Design (AAD). Accuracy and reliability of the process is controlled by means of the analytical software DianaX developed at an earlier stage by the authors. With this new approach the often cumbersome procedure of lighting and thermal exchange calculations can be simplified and made available for the neophyte, with the undeniable advantage of reduced computer time.

scholarly journals Using two-stream theory to capture fluctuations of satellite-perceived TOA SW radiances reflected from clouds over ocean

2020 ◽  
Vol 13 (7) ◽  
pp. 3909-3922
Author(s):  
Florian Tornow ◽  
Carlos Domenech ◽  
Howard W. Barker ◽  
René Preusker ◽  
Jürgen Fischer
Keyword(s):  
Water Vapor ◽  
Radiative Transfer ◽  
State Of The Art ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Cloud Water ◽  
Effective Radius ◽  
The State ◽  
Distribution Models ◽  
New Approach

Abstract. Shortwave (SW) fluxes estimated from broadband radiometry rely on empirically gathered and hemispherically resolved fields of outgoing top-of-atmosphere (TOA) radiances. This study aims to provide more accurate and precise fields of TOA SW radiances reflected from clouds over ocean by introducing a novel semiphysical model predicting radiances per narrow sun-observer geometry. This model was statistically trained using CERES-measured radiances paired with MODIS-retrieved cloud parameters as well as reanalysis-based geophysical parameters. By using radiative transfer approximations as a framework to ingest the above parameters, the new approach incorporates cloud-top effective radius and above-cloud water vapor in addition to traditionally used cloud optical depth, cloud fraction, cloud phase, and surface wind speed. A two-stream cloud albedo – serving to statistically incorporate cloud optical thickness and cloud-top effective radius – and Cox–Munk ocean reflectance were used to describe an albedo over each CERES footprint. Effective-radius-dependent asymmetry parameters were obtained empirically and separately for each viewing-illumination geometry. A simple equation of radiative transfer, with this albedo and attenuating above-cloud water vapor as inputs, was used in its log-linear form to allow for statistical optimization. We identified the two-stream functional form that minimized radiance residuals calculated against CERES observations and outperformed the state-of-the-art approach for most observer geometries outside the sun-glint and solar zenith angles between 20 and 70∘, reducing the median SD of radiance residuals per solar geometry by up to 13.2 % for liquid clouds, 1.9 % for ice clouds, and 35.8 % for footprints containing both cloud phases. Geometries affected by sun glint (constituting between 10 % and 1 % of the discretized upward hemisphere for solar zenith angles of 20 and 70∘, respectively), however, often showed weaker performance when handled with the new approach and had increased residuals by as much as 60 % compared to the state-of-the-art approach. Overall, uncertainties were reduced for liquid-phase and mixed-phase footprints by 5.76 % and 10.81 %, respectively, while uncertainties for ice-phase footprints increased by 0.34 %. Tested for a variety of scenes, we further demonstrated the plausibility of scene-wise predicted radiance fields. This new approach may prove useful when employed in angular distribution models and may result in improved flux estimates, in particular dealing with clouds characterized by small or large droplet/crystal sizes.

New approach for radiative transfer in sea ice and its application for sea ice satellite remote sensing

2013 ◽  
Author(s):  
E. P. Zege ◽  
A. V. Malinka ◽  
I. L. Katsev ◽  
A. S. Prikhach ◽  
G. Heygster
Keyword(s):  
Remote Sensing ◽  
Radiative Transfer ◽  
Sea Ice ◽  
Satellite Remote Sensing ◽  
New Approach

scholarly journals MAX-DOAS measurements of atmospheric trace gases in Ny-Ålesund - Radiative transfer studies and their application

2004 ◽  
Vol 4 (4) ◽  
pp. 955-966 ◽  
Author(s):  
F. Wittrock ◽  
H. Oetjen ◽  
A. Richter ◽  
S. Fietkau ◽  
T. Medeke ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Trace Gases ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Light Sources ◽  
Atmospheric Trace Gases ◽  
New Approach ◽  
Vertical Location

Abstract. A new approach to derive tropospheric concentrations of some atmospheric trace gases from ground-based UV/vis measurements is described. The instrument, referred to as the MAX-DOAS, is based on the well-known UV/vis instruments, which use the sunlight scattered in the zenith sky as the light source and the method of Differential Optical Absorption Spectroscopy (DOAS) to derive column amounts of absorbers like ozone and nitrogen dioxide. Substantial enhancements have been applied to this standard setup to use different lines of sight near to the horizon as additional light sources (MAX - multi axis). Results from measurements at Ny-Ålesund (79° N, 12° E) are presented and interpreted with the full-spherical radiative transfer model SCIATRAN. In particular, measurements of the oxygen dimer O4 which has a known column and vertical distribution in the atmosphere are used to evaluate the sensitivity of the retrieval to parameters such as multiple scattering, solar azimuth, surface albedo and refraction in the atmosphere and also to validate the radiative transfer model. As a first application, measurements of NO2 emissions from a ship lying in Ny-Ålesund harbour are presented. The results of this study demonstrate the feasibility of long term UV/vis multi axis measurement that can be used to derive not only column amounts of different trace gases but also some information on the vertical location of these absorbers.

scholarly journals A Revised Cloud Overlap Scheme for Fast Microwave Radiative Transfer in Rain and Cloud

2009 ◽  
Vol 48 (11) ◽  
pp. 2257-2270 ◽  
Author(s):  
Alan J. Geer ◽  
Peter Bauer ◽  
Christopher W. O’Dell
Keyword(s):  
Radiative Transfer ◽  
Weather Forecasting ◽  
Cloud Fraction ◽  
New Approach ◽  
Microwave Frequencies ◽  
Weather Forecasts ◽  
Clear Sky ◽  
Atmospheric Profile ◽  
Microwave Imager ◽  
Weighted Combination

Abstract The assimilation of cloud- and precipitation-affected observations into weather forecasting systems requires very fast calculations of radiative transfer in the presence of multiple scattering. At the European Centre for Medium-Range Weather Forecasts (ECMWF), performance limitations mean that only a single cloudy calculation (including any precipitation) can be made, and the simulated radiance is a weighted combination of cloudy- and clear-sky radiances. Originally, the weight given to the cloudy part was the maximum cloud fraction in the atmospheric profile. However, this weighting was excessive, and because of nonlinear radiative transfer (the “beamfilling effect”) there were biases in areas of cloud and precipitation. A new approach instead uses the profile average cloud fraction, and decreases RMS errors by 40% in areas of rain or heavy clouds when “truth” comes from multiple independent column simulations. There is improvement all the way from low (e.g., 19 GHz) to high (e.g., 183 GHz) microwave frequencies. There is also improvement when truth comes from microwave imager observations. One minor problem is that biases increase slightly in mid- and upper-tropospheric sounding channels in light-cloud situations, which shows that future improvements will require the cloud fraction to vary according to the optical properties at different frequencies.

A new approach of direction discretization and oversampling for 3D anisotropic radiative transfer modeling

2013 ◽  
Vol 135 ◽  
pp. 213-223 ◽  
Author(s):  
Tiangang Yin ◽  
Jean-Philippe Gastellu-Etchegorry ◽  
Nicolas Lauret ◽  
Eloi Grau ◽  
Jeremy Rubio
Keyword(s):  
Radiative Transfer ◽  
New Approach ◽  
Radiative Transfer Modeling

scholarly journals A Low Memory Solver for Integral Equations of Chandrasekhar Type in the Radiative Transfer Problems

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Mohammed Yusuf Waziri ◽  
Wah June Leong ◽  
Malik Abu Hassan ◽  
Mansor Monsi
Keyword(s):  
Radiative Transfer ◽  
Integral Equations ◽  
Large Scale ◽  
Jacobian Matrix ◽  
Variational Technique ◽  
New Approach ◽  
Numerical Solver ◽  
Transfer Problems ◽  
And Storage ◽  
Jacobian Inverse

The problems of radiative transfer give rise to interesting integral equations that must be faced with efficient numerical solver. Very often the integral equations are discretized to large-scale nonlinear equations and solved by Newton's-like methods. Generally, these kind of methods require the computation and storage of the Jacobian matrix or its approximation. In this paper, we present a new approach that was based on approximating the Jacobian inverse into a diagonal matrix by means of variational technique. Numerical results on well-known benchmarks integral equations involved in the radiative transfer authenticate the reliability and efficiency of the approach. The fact that the proposed method can solve the integral equations without function derivative and matrix storage can be considered as a clear advantage over some other variants of Newton's method.

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