Showing papers on "Radiative transfer published in 1986"
TL;DR: In this paper, a simple model for calculating direct normal and diffuse horizontal spectral solar irradiance for cloudless sky conditions was described. But the model was developed using rigorous radiative transfer codes and limited outdoor measurements.
Abstract: In a previous work, we described a simple model for calculating direct normal and diffuse horizontal spectral solar irradiance for cloudless sky conditions. In this paper, we present a new simple model (SPCTRAL2) that incorporates improvements to the simple model approach and an algorithm for calculating spectral irradiance on tilted surfaces. The model was developed using comparisons with rigorous radiative transfer codes and limited outdoor measurements. SPCTRAL2 produces terrestrial spectra between 0.3 and 4.0 μm with a resolution of approximately 10 nm. Inputs to the model include the solar zenith angle, the collector tilt angle, atmospheric turbidity, the amount of precipitable water vapor and ozone, surface pressure, and ground albedo. A major goal of this work is to provide researchers with the capability to calculate spectral irradiance for different atmospheric conditions and different solar collector geometries using microcomputers.
817 citations
01 Jan 1986
TL;DR: In this article, volume scattering and emission theory are discussed, taking into account a weakly scattering medium, the Born approximation, first-order renormalization, the radiative transfer method, and the matrix-doubling method.
Abstract: Aspects of volume scattering and emission theory are discussed, taking into account a weakly scattering medium, the Born approximation, first-order renormalization, the radiative transfer method, and the matrix-doubling method. Other topics explored are related to scatterometers and probing systems, the passive microwave sensing of the atmosphere, the passive microwave sensing of the ocean, the passive microwave sensing of land, the active microwave sensing of land, and radar remote sensing applications. Attention is given to inversion techniques, atmospheric attenuation and emission, a temperature profile retrieval from ground-based observations, mapping rainfall rates, the apparent temperature of the sea, the emission behavior of bare soil surfaces, the emission behavior of vegetation canopies, the emission behavior of snow, wind-vector radar scatterometry, radar measurements of sea ice, and the back-scattering behavior of cultural vegetation canopies.
778 citations
TL;DR: In this article, the authors presented matrix formulations for the discrete-ordinate and matrix-operator methods of solving the transfer of solar radiation in a plane-parallel scattering atmosphere, where eigenspace transformations of symmetric matrices are introduced into the method of Stamnes and Swanson instead of using the decomposition of an asymmetric matrix.
Abstract: Matrix formulations are presented for the discrete-ordinate and the matrix-operator methods of solving the transfer of solar radiation in a plane-parallel scattering atmosphere. Eigenspace transformations of symmetric matrices are introduced into the method of Stamnes and Swanson instead of using the decomposition of an asymmetric matrix. The computational stability is considerably improved by this algorithm, especially for single-precision calculations. Representations of the reflection and transmission matrices in the matrix-operator method are also given, in terms of the indicated formulations, by considering a boundary-value problem of the discrete-ordinate method. The solutions of the discrete-ordinate method for inhomogeneous atmospheres are given by combining discrete-ordinate solutions for respective homogeneous sublayers through the addition technique of the matrix-operator method.
381 citations
TL;DR: In this paper, the validity of the author's two-temperature, chemical/kinetic model which the author has recently improved is assessed by comparing the calculated results with the existing experimental data for nitrogen in the dissociating and weakly ionizing regime produced behind a normal shock wave.
Abstract: The validity of the author's two-temperature, chemical/kinetic model which the author has recently improved is assessed by comparing the calculated results with the existing experimental data for nitrogen in the dissociating and weakly ionizing regime produced behind a normal shock wave. The computer program Shock Tube Radiation Program (STRAP) based on the two-temperature model is used in calculating the flow properties behind the shock wave and the Nonequilibrium Air Radiation (NEQAIR) program, in determining the radiative characteristics of the flow. Both programs were developed earlier. Comparison is made between the calculated and the existing shock tube data on (1) spectra in the equilibrium region, (2) rotational temperature of the N2(+) B state, (3) vibrational temperature of the N2(+) B state, (4) electronic excitation temperature of the N2 B state, (5) the shape of time-variation of radiation intensities, (6) the times to reach the peak in radiation intensity and equilibrium, and (7) the ratio of nonequilibrium to equilibrium radiative heat fluxes. Good agreement is seen between the experimental data and the present calculation except for the vibrational temperature. A possible reason for the discrepancy is given.
347 citations
TL;DR: In this article, the Bonnor-Thorne approach was used to construct a general radiative solution of the Einstein vacuum equations in harmonic coordinates, which is both past-stationary and past-asymptotically Minkowskian.
Abstract: We present a well-defined formal framework, together with appropriate mathematical tools, which allow us to implement in a constructive way, and to investigate in full
mathematical details, the Bonnor-Thorne approach to gravitational radiation theory. We show how to construct, within this framework, the general radiative (formal) solution of the Einstein vacuum equations, in harmonic coordinates, which is both past-stationary and past-asymptotically Minkowskian. We investigate the
structure of the latter general radiative metric (including all tails and nonlinear effects) both in the near zone and in the far zone. As a side result it is proven that
post-Newtonian expansions must be done by using the gauge functions (lg c)^p/c^n (p, n = positive integers).
302 citations
TL;DR: The branch-cut integral produces a weak late-time radiative power-law decay tail that will characterize the astrophysically observed radiation spectrum for times subsequent to the exponential decay of the quasinormal ringing.
Abstract: The radiative Green's function for the one-dimensional wave equation with the Regge-Wheeler and Zerilli potentials is formally constructed from recently developed analytic representations for generalized spheroidal wave functions, and decomposed into a convergent sum over quasinormal modes, an integral around a branch cut in the frequency domain, and a high-frequency remnant of the free-space propagator. This paper discusses the contribution to the time response made by the quasinormal modes and, at very late times, by the branch-cut integral. The initial-value problem is considered for source fields with both compact and extended radial dependences, and the problem of the formal divergence of the integrals of extended sources over quasinormal-mode wave functions is solved. The branch-cut integral produces a weak late-time radiative power-law decay tail that will characterize the astrophysically observed radiation spectrum for times subsequent to the exponential decay of the quasinormal ringing, when (ct-${r}_{\mathrm{*}}$)\ensuremath{\gg}2MG/${c}^{2}$ and (ct-${r}_{\mathrm{*}}$)/${r}_{\mathrm{*}}$\ensuremath{\ll}1. This radiative decay tail is shown to diminish to Price's nonradiative tail in the final limit ct/${r}_{\mathrm{*}}$\ensuremath{\gg}1. The method is applied to a characteristic-value problem used to model the gravitational collapse of massive stars, and to the small-body radial in-fall problem. The analysis presented is generalizable, through the Newman-Penrose formalism and Teukolsky's equations, to obtain the radiative Green's function for perturbations to the Kerr geometry.
283 citations
TL;DR: In this article, a model is described to estimate hourly or higher frequency diffuse sky radiation impinging on plane surfaces of any orientation, once knowing this value on the horizontal, using a simple geometrical sky hemisphere description, allowing for the observed effects of forward-scattered and backscattered radiation.
274 citations
263 citations
TL;DR: In this article, the matrix elements squared for all (2 → 2) and (2→ 3) parton scattering subprocesses calculated at O(αs3) were presented in n dimensions to regulate singularities due to the emission of soft or collinear radiation.
254 citations
TL;DR: In this paper, a theoretical analysis of diffusion flame extinction in the stagnation point region of a condensed fuel has been made including radiative heat loss from the fuel surface, and the extinction boundary consists of a blowoff and a radiative extinction branch.
187 citations
TL;DR: For a stand of winter wheat, radiative canopy temperature measured with an infra-red radiometer was systematically related to a surface temperature derived from air temperature and wind speed profiles.
Abstract: For a stand of winter wheat, radiative canopy temperature measured with an infra-red radiometer was systematically related to a surface temperature derived from air temperature and wind speed profiles. Radiative temperature changed significantly with viewing angle and azimuth, but the influences of sun angle and ground cover were minimised by inclining the radiometer at 55 ° to the vertical and at right angles to the solar beam.
TL;DR: In this article, the authors measured the radiative heat fluxes between plastic sheet mulches and the soil surface, and found that reflective mulches may reduce the diurnal amplitude of soil temperature, and always reduce the radiant heat gain by the soil.
TL;DR: Doubling method computational results which have yielded plane albedo, total transmission and fractional absorption for plane-parallel atmospheres composed of cloud droplets are presently compared with data obtained with selected radiative transfer approximations.
Abstract: Doubling method computational results which have yielded plane albedo, total transmission and fractional absorption for plane-parallel atmospheres composed of cloud droplets are presently compared with data obtained with selected radiative transfer approximations. The relative and absolute accuracies of asymptotic theory for thick layers and delta-Eddington, Meador-Weaver (1980) and Coakley-Chylek (1975) approximations are compared as a function of optical thickness, solar zenith angle, and single scattering albedo. The delta-Eddington approximation is the most accurate for conservative scattering when the solar zenith angle is small, while Meador-Weaver is the most accurate for nonconservative scattering.
TL;DR: In this paper, the general coupled hydrodynamical-radiative transport equations for neutrino and photon emission from a young, hot neutron star are presented, and it is shown how these equations reduce to those of Salpeter and Shapiro in the plane-parallel, hydrostatic limit.
Abstract: Questions raised by the study of Salpeter and Shapiro (1981) of neutrino and photon emission from a young, hot neutron star are addressed. The general coupled hydrodynamical-radiative transport equations for this emission are presented, and it is shown how these equations reduce to those of Salpeter and Shapiro in the plane-parallel, hydrostatic limit. It is demonstrated that the photon flux cannot be reduced to sub-Eddington levels by discarding the plane-parallel limit and allowing a static atmosphere to puff out to large radius or even by including convective energy transport. This emphasizes the need for dynamical outflow solutions, which are determined numerically. Simple analytic scaling laws which approximate the numerical results are derived. 8 references.
Patent•
25 Jun 1986TL;DR: In this paper, a variety of methods and apparatus for the detection of an analyte of interest in a fluid sample is provided which relies upon the interaction of a fluorophore and a chromophoric light absorbing compound for qualitative and quantitative results.
Abstract: A variety of methods and apparatus for the detection of an analyte of interest in a fluid sample is provided which relies upon the interaction of a fluorophore and a chromophoric light absorbing compound for qualitative and quantitative results. The methods preferably employ fiber optic sensors in combination with fluorophores and/or proto-absorber substances in mobile and immobilized modes of use. The methods and apparatus rely upon the ability of the light absorbing compositions to absorb energy which is transferred either radiatively or non-radiatively by the fluorophore when in an excited state.
01 Jun 1986
TL;DR: Inverse square law for a uniformly bright sphere as discussed by the authors is used to define specific intensity and its moments, which is defined as the specific intensity or brightness of a sphere in terms of specific intensity.
Abstract: Chapter 1 Fundamentals of Radiative Transfer 1.1 The Electromagnetic Spectrum Elementary Properties of Radiation 1.2 Radiative Flux Macroscopic Description of the Propagation of Radiation Flux from an Isotropic Source-The Inverse Square Law 1.3 The Specific Intensity and Its Moments Definition of Specific Intensity or Brightness Net Flux and Momentum Flux Radiative Energy Density Radiation Pressure in an Enclosure Containing an Isotropic Radiation Field Constancy of Specific Intensity Along Rays in Free Space Proof of the Inverse Square Law for a Uniformly Bright Sphere 1.4 Radiative Transfer Emission Absorption The Radiative Transfer Equation Optical Depth and Source Function Mean Free Path Radiation Force 1.5 Thermal Radiation Blackbody Radiation Kirchhoff's Law for Thermal Emission Thermodynamics of Blackbody Radiation The Planck Spectrum Properties of the Planck Law Characteristic Temperatures Related to Planck Spectrum 1.6 The Einstein Coefficients Definition of Coefficients Relations between Einstein Coefficients Absorption and Emission Coefficients in Terms of Einstein Coefficients 1.7 Scattering Effects Random Walks Pure Scattering Combined Scattering and Absorption 1.8 Radiative Diffusion The Rosseland Approximation The Eddington Approximation Two-Stream Approximation Problems References Chapter 2 Basic Theory of Radiation Fields 2.1 Review of Maxwell's Equations 2.2 Plane Electromagnetic Waves 2.3 The Radiation Spectrum 2.4 Polarization and Stokes Parameters 62 Monochromatic Waves Quasi-monochromatic Waves 2.5 Electromagnetic Potentials 2.6 Applicability of Transfer Theory and the Geometrical Optics Limit Problems References Chapter 3 Radiation from Moving Charges 3.1 Retarded Potentials of Single Moving Charges: The Lienard-Wiechart Potentials 3.2 The Velocity and Radiation Fields 3.3 Radiation from Nonrelativistic Systems of Particles Larmor's Formula The Dipole Approximation The General Multipole Expansion 3.4 Thomson Scattering (Electron Scattering) 3.5 Radiation Reaction 3.6 Radiation from Harmonically Bound Particles Undriven Harmonically Bound Particles Driven Harmonically Bound Particles Problems Reference Chapter 4 Relativistic Covariance and Kinematics 4.1 Review of Lorentz Transformations 4.2 Four-Vectors 4.3 Tensor Analysis 4.4 Covariance of Electromagnetic Phenomena 4.5 A Physical Understanding of Field Transformations 129 4.6 Fields of a Uniformly Moving Charge 4.7 Relativistic Mechanics and the Lorentz Four-Force 4.8 Emission from Relativistic Particles Total Emission Angular Distribution of Emitted and Received Power 4.9 Invariant Phase Volumes and Specific Intensity Problems References Chapter 5 Bremsstrahlung 5.1 Emission from Single-Speed Electrons 5.2 Thermal Bremsstrahlung Emission 5.3 Thermal Bremsstrahlung (Free-Free) Absorption 5.4 Relativistic Bremsstrahlung Problems References Chapter 6 Synchrotron Radiation 6.1 Total Emitted Power 6.2 Spectrum of Synchrotron Radiation: A Qualitative Discussion 6.3 Spectral Index for Power-Law Electron Distribution 6.4 Spectrum and Polarization of Synchrotron Radiation: A Detailed Discussion 6.5 Polarization of Synchrotron Radiation 6.6 Transition from Cyclotron to Synchrotron Emission 6.7 Distinction between Received and Emitted Power 6.8 Synchrotron Self-Absorption 6.9 The Impossibility of a Synchrotron Maser in Vacuum Problems References Chapter 7 Compton Scattering 7.1 Cross Section and Energy Transfer for the Fundamental Process Scattering from Electrons at Rest Scattering from Electrons in Motion: Energy Transfer 7.2 Inverse Compton Power for Single Scattering 7.3 Inverse Compton Spectra for Single Scattering 7.4 Energy Transfer for Repeated Scatterings in a Finite, Thermal Medium: The Compton Y Parameter 7.5 Inverse Compton Spectra and Power for Repeated Scatterings by Relativistic Electrons of Small Optical Depth 7.6 Repeated Scatterings by Nonrelativistic Electrons: The Kompaneets Equation 7.7 Spectral Regimes for Repeated Scattering by Nonrelativistic Electrons Modified Blackbody Spectra y"1 Wien Spectra y"1 Unsaturated Comptonization with Soft Photon Input Problems References Chapter 8 Plasma Effects 8.1 Dispersion in Cold, Isotropic Plasma The Plasma Frequency Group and Phase Velocity and the Index of Refraction 8.2 Propagation Along a Magnetic Field Faraday Rotation 8.3 Plasma Effects in High-Energy Emission Processes Cherenkov Radiation Razin Effect Problems References Chapter 9 Atomic Structure 9.1 A Review of the Schrodinger Equation 9.2 One Electron in a Central Field Wave Functions Spin 9.3 Many-Electron Systems Statistics: The Pauli Principle Hartree-Fock Approximation: Configurations The Electrostatic Interaction LS Coupling and Terms 9.4 Perturbations, Level Splittings, and Term Diagrams Equivalent and Nonequivalent Electrons and Their Spectroscopic Terms Parity Spin-Orbit Coupling Zeeman Effect Role of the Nucleus Hyperfine Structure 9.5 Thermal Distribution of Energy Levels and Ionization Thermal Equilibrium: Boltzmann Population of Levels The Saha Equation Problems References Chapter 10 Radiative Transitions 10.1 Semi-Classical Theory of Radiative Transitions The Electromagnetic Hamiltonian The Transition Probability 10.2 The Dipole Approximation 10.3 Einstein Coefficients and Oscillator Strengths 10.4 Selection Rules 10.5 Transition Rates Bound-Bound Transitions for Hydrogen Bound-Free Transitions (Continuous Absorption) for Hydrogen Radiative Recombination - Milne Relations The Role of Coupling Schemes in the Determination of f Values 10.6 Line Broadening Mechanisms Doppler Broadening Natural Broadening Collisional Broadening Combined Doppler and Lorentz Profiles Problems References Chapter 11 Molecular Structure 11.1 The Born-Oppenheimer Approximation: An Order of Magnitude Estimate of Energy Levels 11.2 Electronic Binding of Nuclei The H2+ Ion The H2 Molecule 11.3 Pure Rotation Spectra Energy Levels Selection Rules and Emission Frequencies 11.4 Rotation-Vibration Spectra Energy Levels and the Morse Potential Selection Rules and Emission Frequencies 11.5 Electronic-Rotational-Vibrational Spectra Energy Levels Selection Rules and Emission Frequencies Problems References Solutions Index
TL;DR: In this paper, the authors show that the electronic transition moment for the NO γ bands excited by energy transfer from metastable nitrogen molecules varies by about 40% over the r−centroid range of 1.13−0.97 A.
Abstract: Branching ratio measurements for the NO γ bands excited by energy transfer from metastable nitrogen molecules show that the electronic transition moment for the NO(A 2Σ+–X 2Π) transition varies by about 40% over the r‐centroid range of 1.13–0.97 A. Combining this transition‐moment variation with radiative lifetime measurements provides a complete set of Einstein coefficients for NO(A–X) transitions from v’=0–2.
TL;DR: In this article, the Arctic Stratus Experiment was used to determine the interactions between mixing, radiative transfer, and cloud microphysics for four cloud decks, including liquid water fluxes.
Abstract: The Arctic Stratus Experiment, conducted during June 1980 over the Beaufort Sea, produced an extensive set of simultaneous measurements of boundary layer structure, radiation fluxes, and cloud microphysical properties. In this paper these data are used to determine the interactions between mixing, radiative transfer, and cloud microphysics for four cloud decks. The thermodynamic structure and fluxes of the thermodynamic quantities in the cloudy boundary layer are examined, including liquid water fluxes. Net radiative heating profiles are also determined. A detailed analysis of the fine-scale structure of the cloud microphysics is presented, including correlations between the cloud microphysical parameters (droplet concentration, liquid water content, mean radius, spectral dispersion, and the 95% volume liquid water drop radius), which are used to infer the nature of the mixing processes and the local effects of radiative heating/cooling. A comparison is then made with other observations and exist...
TL;DR: In this paper, a procedure for deriving the stellar radiation field incident on the inner edge of the shell is developed, and the temperature correction procedure of Cassinelli and Hartmann (1975) for extended stellar atmospheres is modified so that the multitemperature nature of the grains in the cloud may be derived.
Abstract: Radiation transfer problems involved in the infall of dust and gas during star formation are studied. Dust properties are discussed, and modifications of spherical radiative transfer equations are presented that permit forward scattering by dust to be treated for the small size of the star relative to the inner radius of the shell. A procedure for deriving the stellar radiation field incident on the inner edge of the shell is developed. The temperature correction procedure of Cassinelli and Hartmann (1975) for extended stellar atmospheres is modified so that the multitemperature nature of the grains in the cloud may be derived. Temperature distributions for three schematic models in which the density is prespecified are discussed. Radiative acceleration of grains is addressed, showing that the proper mean opacity differs by a large factor from the Rosseland mean opacity that is commonly used. Emergent fluxes for the models are given.
TL;DR: In this article, the effect of varying the assumption for the overlap of partially cloudy layers, and the resultant impact upon the heating rate profile, planetary albedo, net flux at the surface, and atmospheric net absorption were studied.
Abstract: Using the shortwave radiation scheme of Fouquart and Bonnel that accounts for scattering and absorption by gases and cloud particles, we study the effect of varying the assumption for the overlap of partially cloudy layers, and the resultant impact upon the heating rate profile, planetary albedo, net flux at the surface, and atmospheric net absorption. In this study, we consider the maximum, minimum, and random overlap assumptions and a radically simple scheme to approximate the radiative effects of a random overlapping of clouds. This simple scheme involves linear combinations of clear and cloudy reflectivities and transmissivities within a layer, and gives, respectively, fluxes and heating rates with maximum differences of 5% and 0.1 K day−1 compared to similar quantities obtained from a full calculation assuming a random overlapping of cloud layers. This former approach, however, is much more time efficient (five times faster for a 3-cloud atmosphere, three times faster in a full-size GCM). Co...
TL;DR: In this article, the authors used Mie scattering theory to calculate the independent scattering and absorption coefficients of a packed-sphere system, and derived the dependent scattering efficiency using a pair distribution function to correlate the relative positions of the constituent particles in the system.
Abstract: The present work predicts radiative extinction characteristics of packed-sphere systems; both independent and dependent scattering are considered. This pertains to many radiation and heat transfer applications including packed and fluidized beds, microsphere insulations, and soot or paint layers. Mie scattering theory is used to calculate the independent scattering and absorption coefficients of a packed-sphere system. Radiative transfer predictions based on these coefficients and a simple two-flux model provide much better agreement with reliable experimental data than published ray-tracing and Monte Carlo models. The dependent scattering efficiency is calculated via the form factor technique of X-ray scattering theory, which uses a pair distribution function to correlate the relative positions of the constituent particles in the system. Predictions using two-pair distribution functions, a "modified-liquid" model, and the hard-sphere Percus-Yevick model show excellent agreement with published experimental data. a a
CERN1
Book•
01 Apr 1986
TL;DR: In this article, the basic relations between the Earth's surface and its atmosphere have been discussed, including the propagation of Electromagnetic Waves, propagation of electromagnetic waves at boundary between different media, wave propagation, and scattering of radiation by macroscopic particles.
Abstract: 1 Some Basic Relations.- 1.1 Natural Parameters and Observables.- 1.2 Propagation of Electromagnetic Waves.- 1.3 Waves at Boundaries Between Different Media.- 2 Spectral Lines of Atmospheric Gases.- 2.1 Resonant Frequencies of Molecules.- 2.2 Widths of Spectral Lines.- 2.3 Applications to the Earth's Atmosphere.- 3 Spectral Properties of Condensed Matter.- 3.1 Elementary Theory of Organic Dyes.- 3.2 Chlorophyll and Spectral Properties of Plants.- 3.3 Polarization of the Media and Dispersion of Radiation.- 4 Scattering of Radiation.- 4.1 Light Scattering by Molecules.- 4.2 Scattering of Radiation by Macroscopic Particles.- 4.3 Backscattering from Rough Surfaces.- 5 Transport of Radiation.- 5.1 The Equation of Radiative Transfer.- 5.2 Kirchhoff's Law and Radiometry.- 5.3 Radiometric Observation of Atmospheric Parameters and the Inversion of Remotely Sensed Data.- References.
TL;DR: In this paper, an emissivity approach is taken to modeling fluxes and cooling rates in the atmosphere, and a nonisothermal water vapor long wave radiation emissivities and absorptivity model is developed.
Abstract: An emissivity approach is taken to modeling fluxes and cooling rates in the atmosphere. The nonisothermal water vapor long wave radiation emissivity and absorptivity model that is developed satisfies the requirements of defining a monochromatic transfer equation for predicting water vapor emissions. Predictions made with the model compare favorably with fluxes predicted by a radiation model for narrow-band emissions in 5 kayser intervals. The spectral resolution assumed in narrow-band models is shown to be an arbitrary parameter and, if a far wing continuum-type opacity is included in the emissivity scheme presented, results can be obtained which are as accurate as predictions made with state of the art line-by-line (LBL) calculations.
TL;DR: In this paper, the zonally averaged radiative balance of the stratosphere based on the measured temperature structure and gas concentrations available from the LIMS instrument is examined in detail.
Abstract: The zonally averaged radiative balance of the stratosphere based on the measured temperature structure and gas concentrations available from the LIMS instrument is examined in detail. These data are extant for seven months (November 1978 to May 1979). The contribution to the net radiative balance due to the individual components of solar heating and longwave cooling is discussed. These components are further broken down by individual gas constituent to understand the role each gas plays in determining the total radiative heating/cooling. The deficiencies of employing a latitudinally and temporally independent Newtonian damping coefficient are also explored. In particular, the Newtonian damping time is shown to vary by a factor of two in both latitude and season. Net zonally averaged stratospheric radiative heating for the seven months of LIMS data are presented. These net heating rates are important in determining the role of advective transport of chemical constituents. An important feature that appears in the derived radiative heating is the existence of a region of net radiative cooling near the equatorial stratopause.
TL;DR: In this article, radio wave propagation through electron-density fluctuations in the ISM is studied using a one-dimensional thin-screen model for the turbulent medium, and the importance of various effects for timing and scintillation observations of pulsars, VLBI observations of galactic and extragalactic radio sources, and for variability measurements of extragaleactic sources is assessed.
Abstract: Radio wave propagation through electron-density fluctuations in the ISM is studied. Observable propagation effects are explored using a one-dimensional thin-screen model for the turbulent medium. Diffraction caused by stochastic small-scale irregularities is combined with refraction from deterministic large-scale irregularities. Some of the effects are illustrated with numerical simulations of the wave propagation. Multiple imaging is considered, delineating the possible effects and discussing their extensions to two-dimensional screens and extended three-dimensional media. The case where refraction as well as diffraction is caused by a stochastic medium with a spectrum of a given form is considered. The magnitudes of observable effects is estimated for representative spectra that may be relevant to the ISM. The importance of the various effects for timing and scintillation observations of pulsars, VLBI observations of galactic and extragalactic radio sources, and for variability measurements of extragalactic sources is assessed. 47 references.
TL;DR: In this paper, the problem of radiative transfer through a fibrous medium has been formulated rigorously to account for the orientation of the fibers, and it is shown that the radiative properties of the medium are strongly dependent on the fiber orientation.
Abstract: The problem of radiative transfer through a fibrous medium has been formulated rigorously to account for the orientation of the fibers. The fibers in the medium can be either randomly oriented or aligned. It is shown that the radiative properties of the medium, e.g. the extinction efficiency, are strongly dependent on the fiber orientation. A specific case of collimated irradiation on the fibrous medium with fibers randomly oriented in a plane is investigated. Parametric studies are performed to determine the effect of fiber size and fiber optical properties on the transmissivity and reflectivity of the medium.
03 Jan 1986
TL;DR: In this paper, the optical and radiative properties of a desert aerosol model based on the recommendations made by the IAMAP Radiation Commission were investigated and two models were discussed representing the extremes of background conditions and a severe dust storm.
Abstract: : One of the major sources of the natural atmospheric aerosols is wind- blown dust and sand These predominantly originate from the arid and semi-arid regions which make up one-third of the earth's land area The aerosol models in the Standard Radiation Atmospheres (SRA) of the IAMAP Radiation Commission, do not include a model specifically representative of these regions Several recommendations were made for developing such a seperate desert aerosol model This paper presents the optical and radiative properties of a desert aerosol model based on those recommendations Two models are discussed representing the extremes of background conditions and a severe dust storm Keywords: Desert aerosols; Optical properties; Scattering;Transmission; Atmospheric radiation; Reprints
TL;DR: Three- and two-flux models for solving the scattering transfer equation in terms of Lorenz-Mie parameters are derived from the general formulas and the connection with classical literature is pointed out.
Abstract: In a previous paper, four-flux models for solving the scattering transfer equation in terms of Lorenz-Mie parameters were designed for Lorenz-Mie scatter centers embedded in a slab. Formulas for the various transmittances and reflectances were established. The special cases of transparent and nonscattering particles require special treatments which are described in the present work and lead to simpler formulas. The special case of completely opaque atmospheres is also considered. Three- and two-flux models are derived from the general formulas. The connection with classical literature is pointed out.