Radiative transfer analysis on the internal optical-path of FTIR spectrometer for transmission measurements of absorbing media

2021 ◽  
Vol 114 ◽  
pp. 103650
Author(s):  
Meng Liu ◽  
Xin-Lin Xia ◽  
Qing Ai ◽  
Shuai Wang
Keyword(s):  
Radiative Transfer ◽  
Optical Path ◽  
Ftir Spectrometer ◽  
Transmission Measurements ◽  
Absorbing Media

scholarly journals Medium Resolution Transmission Measurements of Water Vapor at High Temperature

2005 ◽  
Author(s):  
Sudarshan P. Bharadwaj ◽  
Michael F. Modest ◽  
Robert J. Riazzi
Keyword(s):  
Water Vapor ◽  
High Temperature ◽  
High Resolution ◽  
Measured Data ◽  
Drop Tube ◽  
Medium Resolution ◽  
Ftir Spectrometer ◽  
Transmission Measurements ◽  
Vibration Rotation ◽  
High Temperature Gas

Medium resolution transmissivities of water vapor were measured at temperatures between 600 K and 1550 K for all important vibration-rotation bands as well as part of the purely rotational band. Measurements were made with an improved drop tube design, which guarantees a truly isothermal high-temperature gas column. Data were collected with an FTIR-spectrometer, allowing for much better spectral resolution than most previous high-temperature measurements. The measured data were compared with the HITEMP database, as well as with the data of Phillips for the 2.7 μm band of H2O. The data show minor discrepancies with the high-resolution database, particularly at higher temperatures, but in general agreement is acceptable.

scholarly journals Impact of 3D radiative transfer on airborne NO<sub>2</sub> imaging remote sensing over cities with buildings

2021 ◽  
Vol 14 (10) ◽  
pp. 6469-6482
Author(s):  
Marc Schwaerzel ◽  
Dominik Brunner ◽  
Fabian Jakub ◽  
Claudia Emde ◽  
Brigitte Buchmann ◽  
...  
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Radiative Transfer ◽  
Urban Canopy ◽  
Optical Path ◽  
Monte Carlo Code ◽  
Transfer Effects ◽  
Noise Component ◽  
Resolution Model ◽  
Airborne Imaging

Abstract. Airborne imaging remote sensing is increasingly used to map the spatial distribution of nitrogen dioxide (NO2) in cities. Despite the small ground-pixel size of the sensors, the measured NO2 distributions are much smoother than one would expect from high-resolution model simulations of NO2 over cities. This could partly be caused by 3D radiative transfer effects due to observation geometry, adjacency effects and effects of buildings. Here, we present a case study of imaging a synthetic NO2 distribution for a district of Zurich using the 3D MYSTIC (Monte carlo code for the phYSically correct Tracing of photons In Cloudy atmospheres) solver of the libRadtran radiative transfer library. We computed NO2 slant column densities (SCDs) using the recently implemented 3D-box air mass factors (3D-box AMFs) and a new urban canopy module to account for the effects of buildings. We found that for a single ground pixel (50 m × 50 m) more than 50 % of the sensitivity is located outside of the pixel, primarily in the direction of the main optical path between sun, ground pixel, and instrument. Consequently, NO2 SCDs are spatially smoothed, which results in an increase over roads when they are parallel to the optical path and a decrease otherwise. When buildings are included, NO2 SCDs are reduced on average by 5 % due to the reduced sensitivity to NO2 in the shadows of the buildings. The effects of buildings also introduce a complex pattern of variability in SCDs that would show up in airborne observations as an additional noise component (about 12 µmol m−2) similar to the magnitude of typical measurement uncertainties. The smearing of the SCDs cannot be corrected using 1D-layer AMFs that assume horizontal homogeneity and thus remains in the final NO2 map. The 3D radiative transfer effects by including buildings need to be considered to compute more accurate AMFs and to reduce biases in NO2 vertical columns obtained from high-resolution city-scale NO2 remote sensing.

Transient Discrete Ordinate Method and Experiments of Pulsed Radiative Transfer Through Scattering Absorbing Media

Volume 4 ◽  
2004 ◽  
Author(s):  
Ashish Trivedi ◽  
Soumyadipta Basu ◽  
Kunal Mitra
Keyword(s):  
Radiative Transfer ◽  
Pulse Laser ◽  
Transfer Equation ◽  
Radiative Transfer Equation ◽  
Short Pulse ◽  
Laser Source ◽  
Discrete Ordinates ◽  
Experimental Measurements ◽  
Short Pulse Laser ◽  
Absorbing Media

The objective of this paper is to validate the solution of transient radiation transfer equation with experimental measurements using short pulse laser source having a Gaussian distribution. The transient radiative transfer equation for the case of short pulse laser propagation through scattering absorbing media such as tissue is an integrodifferential equation and is therefore complicated to solve. The time-dependent discrete ordinates method in conjunction with high order upwind piecewise parabolic interpolation scheme is used to solve the transient radiative transfer equation for the case of anisotropically scattering absorbing medium having a rectangular geometry in which an inhomogeneity is embedded. A parametric study involving different scattering and absorption coefficients of the medium, inhomogeneity and inhomogeneity size as well as the detector position is performed. The numerical modeling results and experimental measurements are in excellent agreement for various parameters studied in this paper.

An evolutionary algorithm for controlling numerical convergence of the radiative transfer equation with participating media using TVD interpolation schemes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Carlos Enrique Torres-Aguilar ◽  
Pedro Moreno-Bernal ◽  
Jesús Xamán ◽  
Ivett Zavala Guillen ◽  
Irving Osiris Hernández-López
Keyword(s):  
Radiative Transfer ◽  
Numerical Solution ◽  
Evolutionary Algorithm ◽  
Transfer Equation ◽  
Radiative Transfer Equation ◽  
Scattering Media ◽  
Content Type ◽  
Cpu Time ◽  
Absorbing Media ◽  
Relaxation Coefficients

Purpose This paper aims to present an evolutionary algorithm (EA) to accelerate the convergence for the radiative transfer equation (RTE) numerical solution using high-order and high-resolution schemes by the relaxation coefficients optimization. Design methodology/approach The objective function minimizes the residual value difference between iterations in each control volume until its difference is lower than the convergence criterion. The EA approach is evaluated in two configurations, a two-dimensional cavity with scattering media and absorbing media. Findings Experimental results show the capacity to obtain the numerical solution for both cases on all interpolation schemes tested by the EA approach. The EA approach reduces CPU time for the RTE numerical solution using SUPERBEE, SWEBY and MUSCL schemes until 97% and 135% in scattering and absorbing media cases, respectively. The relaxation coefficients optimized every two numerical solution iterations achieve a significant reduction of the CPU time compared to the deferred correction procedure with fixed relaxation coefficients. Originality/value The proposed EA approach for the RTE numerical solution effectively reduces the CPU time compared to the DC procedure with fixed relaxation coefficients.

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