共查询到20条相似文献，搜索用时 31 毫秒
1.
A new way is adopted for the evaluation of the upwelling radiation from atmosphere bounded by two half-Lambert surfaces. The atmosphere is assumed to be homogeneous, and is composed of aerosol, molecules, and absorbent gases, where the model aerosol is of the oceanic and water soluble types.In the computational procedure, an iterative doubling-adding equation is expanded into a series of the radiative interaction modes between atmosphere and surface. Next, a probability of radiation interacting with respective half surfaces is calculated based on the assumption of single-scattering in the atmosphere. On the basis of this probability, the emergent radiation at the top of the atmosphere is approximately calculated by considering the radiative intractions to be twice as large. The effect of the multiple-scattering is fully taken into account. A numerical simulation exhibits the extraordinary effect near the two half-surface boundary of different albedoes. The effect of the other half-surface on the radiance decreases monotonically with the distance from the boundary. The present new version enable us to quantitatively discuss radiative transfer near the boundary of two half-surfaces even if the optical thickness is large and (or) surface albedo is great. 相似文献
2.
For the evaluation of the effect of the non-uniform surface albedo on the emergent radiation from the atmosphere, the emergent radiation from the atmosphere bounded by the two half Lambert surfaces composed of different albedo is computed. This paper is the improved version of the previous paper (Takashima and Masuda, 1991). The atmosphere is assumed to be homogeneous, which is composed of aerosol, molecules, and absorbent gases. Their optical thicknesses are (1) 0.25, 0.23, and 0.02, and (2) 0.75, 0.23, and 0.02, respectively. The model aerosol is of the oceanic and water soluble types.In the computational procedure, the emergent radiation is calculated approximately by the contributions due to the multiple scattering in the atmosphere, and due to the diffusely or directly transmitted radiation through the atmosphere which is reflected by the surfaces once (4 interactive radiative modes between atmosphere and surface). Furthermore, to perform the hemispherical integration processing the radiative interaction, the transmission function based on the single scattering in the atmosphere is introduced and then the transmission function is averaged over the hemisphere with weighting function. The numerical simulation exhibits the extraordinary effect near the two half surface boundary of different albedoes. The effect decreases exponentially with the distance from the boundary. The effect depends on the atmospheric aerosol type, optical thickness, and surface albedo. The present version enables us to quantitatively discuss the radiative transfer trend near the boundary of two half surfaces. The upward radiance would simply be evaluated using the present scattering approximation method if the surface albedo is less than 0.3. The present method is thought of as a first step extending the one-dimensional radiative transfer model to two-dimensional using the doubling-adding method. 相似文献
3.
A new version is adopted for the evaluation of the upwelling radiation from atmosphere bounded by the surface, where the surface is composed of two half semi-infinite Lambert surfaces and a stream is inserted between them. The contrast of the stream is discussed with respect to the atmospheric effect. The width of the stream is considered to be 0.5, 1, and 3km; The solar and observational direction is located in the normal plane to the stream. The observational site is located at altitude 30km. The horizontal distance of observational site to the stream is fixed to 6.28 . The atmosphere is assumed to be homogeneous, which is composed of aerosol and molecules, where the model aerosol is of the oceanic type.In the computational procedure, a probability of radiation interacting with respective half surfaces and the stream are calculated based on the assumption of single scattering in the atmosphere, where isotropic scattering is undertaken. By use of this probability, the emergent radiation at the top of the atmosphere is calculated approximately by considering the radiative interactions between atmosphere and surfaces up to twice. The numerical simulation exhibits the extraordinary effect near the stream. The contrast of the stream depends upon the albedo of the surrounding surfaces. It increases with the increase of the stream width and decreases with the optical thickness. 相似文献
4.
For the evaluation of the effect of the nonuniform surface albedo to the emergent radiation from the atmosphere, the emergent radiation from the atmosphere bounded by the two-halves of the Lambert surface with different albedos is computed. The principal plane is assumed to be perpendicular to the boundary of surfaces. The atmosphere is assumed to be homogeneous, which is composed of aerosol, molecules, and absorbent gases. Their optical thicknesses are 0.25, 0.23, and 0.02, respectively. The model aerosol is of the oceanic and water soluble types.In the computational procedure, the emergent radiation is approximated by the contributions due to the multiple scattering in the atmosphere, directly attenuated radiation, and radiation due to single scattering in the atmosphere which is reflected by the Lambert surface (up to 4 interactive radiative modes between atmosphere and surface). For quantitative analysis, results are compared with those of the atmosphere-uniform surface model, where the multiple scattering is considered. The numerical simulation exhibits the extraordinary effect near the surface boundary of different albedos. The effect decreases exponentially with the distance from the boundary. It is a function of the observational position, difference of surface albedos, optical thickness and aerosol type.The upward radiance would simply be evaluated using the present scattering approximation method if the atmosphere is in clear condition. Whereas in hazy condition, the effect of multiple scattering in the atmosphere should be considered more precisely, since the upward radiance exhibit a strong dependence on observational nadir angles due to multiple scattering in the atmosphere. Furthermore, it depends on the optical characteristics of aerosols. 相似文献
5.
A new method for simulation of atmospheric effect on the emergent radiation over non-uniform terrain
For a precise atmospheric correction over the non-uniform terrain in satellite imageries, a numerical method for evaluating the upwelling radiation at the top of the atmosphere bounded by the non-uniform surface is developed as an extended doubling-adding method. The present method enable us to treat quantitatively the case of hazy atmosphere and (or) large albedo of the surface. 相似文献
6.
K. L. Coulson 《Planetary and Space Science》1959,1(4):277-284
The solution of the equation of radiative transfer in a medium exhibiting Rayleigh scattering, as developed by S. Chandrasekhar, has been used for an extensive series of computations(3) of the characteristics of the scattered and diffusely reflected radiation emerging from the top of an atmospheric model which corresponds in many respects to the sunlit portion of the earth's atmosphere. The first part of this two-part discussion dealt with the intensity, degree of polarization, plane of polarization and the neutral points of the emergent light as functions of sun elevation, direction in the downward hemisphere, optical thickness of the model atmosphere and reflectivity of the underlying surface. This second part is concerned with the upward flux obtained by an integration of the intensity over the entire hemisphere, for the incident radiation (a) being independent of wavelength or (b) having the spectral distribution of the extra-terrestrial solar radiation. Integration with respect to wavelength in the latter case, together with an approximation for the sphericity of the atmosphere, yields a value of 7.6 per cent for the earth's planetary albedo due to scattering by the clear atmosphere. An approximation for ozone absorption decreases the computed albedo to 6.9 per cent. 相似文献
7.
Atmospheres and spectra of strongly magnetized neutron stars 总被引：1，自引：0，他引：1
We construct atmosphere models for strongly magnetized neutron stars with surface fields and effective temperatures . The atmospheres directly determine the characteristics of thermal emission from isolated neutron stars, including radio pulsars, soft gamma-ray repeaters, and anomalous X-ray pulsars. In our models, the atmosphere is composed of pure hydrogen or helium and is assumed to be fully ionized. The radiative opacities include free–free absorption and scattering by both electrons and ions computed for the two photon polarization modes in the magnetized electron–ion plasma. Since the radiation emerges from deep layers in the atmosphere with , plasma effects can significantly modify the photon opacities by changing the properties of the polarization modes. In the case where the magnetic field and the surface normal are parallel, we solve the full, angle-dependent, coupled radiative transfer equations for both polarization modes. We also construct atmosphere models for general field orientations based on the diffusion approximation of the transport equations and compare the results with models based on full radiative transport. In general, the emergent thermal radiation exhibits significant deviation from blackbody, with harder spectra at high energies. The spectra also show a broad feature around the ion cyclotron resonance , where Z and A are the atomic charge and atomic mass of the ion, respectively; this feature is particularly pronounced when . Detection of the resonance feature would provide a direct measurement of the surface magnetic fields on magnetars. 相似文献
8.
In this work, we describe an analysis of the internal solar radiation fields in Saturn's atmosphere. The aim of this paper is to study how the solar radiation flux in optical wavelengths (0.25-1.0 μm) is attenuated, primarily by the effect of the aerosols located close to the tropopause level, retrieving also the corresponding solar heating rates. We use a doubling-adding method and previous results on the vertical cloud and haze structure of Saturn's atmosphere. Our study shows that the maximum penetration level (∼250 mbar) for these wavelengths is substantially higher than previously expected because of the huge optical thickness of the tropospheric haze described in all vertical cloud structure models. We compare our results with previous estimates and parameterizations for seasonal climate models and propose a new approach for future models, with an intense and concentrated heating rate close to the top level of the tropospheric haze. Given that our spectral range accounts for about the 70% of the total solar flux, and using previous estimates for the penetration levels of infrared radiation in Saturn's atmosphere, we conclude solar radiation effect is negligible at levels below 600 mbar. This result is fundamental for understanding the role of solar radiation in the general atmospheric circulation of Saturn. 相似文献
9.
A. Peraiah 《Astrophysics and Space Science》1973,21(1):223-235
The effects of curvature in an atmosphere with pure absorption are investigated. Numerical solution of the transfer equation has been obtained in the framework of the Discrete Space Theory of Radiative Transfer. Two cases have been considered: (a) the atmosphere is irradiated at the bottom and there is no incident radiation at the top of the atmosphere; and (b) no radiation is incident on either side of the atmosphere. It is found that the thermal sources inside the atmosphere dominantly influence the emergent radiation and this is very much so, in the spherical case and for large optical thickness. The emergent luminosities increase with the geometrical thickness although the emergent specific intensities are reduced and the former seems to be because of the larger surface area and later seems to be because of the effects of curvature. 相似文献
10.
A method of computing the diffuse reflection and transmission radiation by an inhomogeneous, plane-parallel planetary atmosphere with internal emission source is discussed by use of the adding method. If the atmosphere is simulated by a number of homogeneous sub-layers, the radiation diffusely reflected or transmitted by the atmosphere can be expressed in terms of the reflection and transmission matrices of the radiation of sub-layers. The diffusely transmitted radiation due to the internal emission source can be also easily computed in the same manner. These equations for the emergent radiation are in a quite general form and are applicable to radiative transfer in the atmosphere in the region from ultraviolet to infrared radiation. With this method, the tiresome treatment due to the polarity effect of radiation is overcome. 相似文献
11.
Tsutomu Takashima 《Earth, Moon, and Planets》1985,33(1):59-97
A procedure of computing the radiance and the polarization parameters of radiation diffusely reflected and transmitted by an inhomogeneous, plane-parallel terrestrial atmosphere bounded by a ruffled ocean surface is discussed with the aid of the adding method. If the atmosphere and the ocean are simulated by a number of homogeneous sublayers, the matrices of radiation reflected and transmitted diffusely by the atmosphere-ocean system can be expressed in terms of these matrices of sublayers by using only a couple of iterative equations in which the polarity effect of radiation is included. Furthermore, the upwelling radiance and the polarization degree of radiation at the top of the atmosphere can be calculated by using a single iterative equation without requiring the equation for the diffuse transmission matrix of radiation. The ruffled ocean surface can be treated as an interacting interface, where the transmitted radiation from beneath the ocean surface into the atmosphere is also taken into account into the derivation of equations. Finally, sample computations of the upwelling radiance and the polarization degree of radiation from the top of the atmosphere are carried out at the wavelength of 0.60 micron. 相似文献
12.
Sonoyo Mukai 《Astrophysics and Space Science》1977,51(1):165-172
In the present paper, the intensity of radiation emergent from the atmosphere bounded by a rough surface is discussed with the aid of the superposition method derived by Mukai (1973). The merit of this method is to express the laws of diffuse reflection and transmission for the planetary problem with a rough surface in terms of a scattering and a transmission function for the standard problem.Here the bottom surface is assumed to reflect light in accordance with the slope distribution given by Cox and Munk (1954a, b). The results are discussed in terms of the optical properties and roughness of the bottom surface. 相似文献
13.
Tõnu Viik 《Earth, Moon, and Planets》1990,49(2):149-161
The vector equation of radiative transfer is solved for non-conservative homogeneous plane-parallel atmosphere using the method of discrete ordinates. The scattering processes in the atmosphere bounded by a Lambert bottom are described by the Rayleigh-Cabannes phase matrix. The primary radiation field is generated by constant internal sources. A package of FORTRAN subroutines is compiled to find the axial radiation field for such an atmosphere at arbitrary optical depth. 相似文献
14.
Romuald Tapimo Hervé Thierry Tagne Kamdem David Yemele 《Astrophysics and Space Science》2018,363(3):52
A discrete spherical harmonics method is developed for the radiative transfer problem in inhomogeneous polarized planar atmosphere illuminated at the top by a collimated sunlight while the bottom reflects the radiation. The method expands both the Stokes vector and the phase matrix in a finite series of generalized spherical functions and the resulting vector radiative transfer equation is expressed in a set of polar directions. Hence, the polarized characteristics of the radiance within the atmosphere at any polar direction and azimuthal angle can be determined without linearization and/or interpolations. The spatial dependent of the problem is solved using the spectral Chebyshev method. The emergent and transmitted radiative intensity and the degree of polarization are predicted for both Rayleigh and Mie scattering. The discrete spherical harmonics method predictions for optical thin atmosphere using 36 streams are found in good agreement with benchmark literature results. The maximum deviation between the proposed method and literature results and for polar directions \(\vert \mu \vert \geq0.1 \) is less than 0.5% and 0.9% for the Rayleigh and Mie scattering, respectively. These deviations for directions close to zero are about 3% and 10% for Rayleigh and Mie scattering, respectively. 相似文献
15.
The coupled set of equations of hydrodynamics and radiative transfer is derived for small disturbances in a plane, grey atmosphere. Only radiative transfer is taken into account in the energy equation; dynamical effects of radiation are ignored. A mean stationary radiative flux through the photosphere is taken into account. The radiative transfer equation is used by assuming the Eddington approximation, moreover, an exponential height profile of the temperature and an analytical opacity formula are supposed. For this model we obtained an asymptotic solution for plane nonadiabatic acoustic waves and radiation waves. The approach provides a detailed discussion of the interaction of nonadiabatic p‐modes and radiation waves in a realistic model of the photosphere of a solar‐like star. 相似文献
16.
Tsutomu Takashima 《Astrophysics and Space Science》1975,36(2):319-328
The procedure of computing the intensity and the polarization parameters of radiation diffusely reflected and transmitted by an inhomogeneous, plane-parallel planetary atmosphere is discussed with the aid of the adding method. If the atmosphere is simulated by a number of homogeneous sublayers (aerosols and ozone may be included), the matrices of radiation diffusely reflected and transmitted by the atmosphere can be expressed in terms of these matrices of sublayers by using only a couple of iterative equations with the polarity effect of radiation. This procedure is to be extended to the model atmosphere bounded by the surface reflector with a quite arbitrary phase matrix. 相似文献
17.
The upwelling radiation at the top of the atmosphere is computed over a circular lake which is located in the uniform Lambert surface, using a modified version of the doubling-adding method. The radiance over the lake is discussed with respect to the atmospheric effect. The radius of the lake is assumed to be 0.5, 1, and 3 km. The observational site is located at altitude 30 km. The zenith of the observational site is located in the plane which is determined by the zenith of the center of the lake and incident solar direction. The zenith angle of the observational site to the center of the lake is fixed to 6.28°. The atmosphere is assumed to be homogeneous, which is composed of aerosol and molecule, where the model aerosol is of the oceanic or the water soluble types.Numerical simulation exhibits an extraordinary effect near the lake. The radiance of the lake against the surrounding depends upon the albedo of the surrounding surface. It increases with the increase of the size of the lake and decreases with the optical thickness. At large optical depth, the radiance depends upon the aerosol characteristics. It shows little dependence on the solar zenith angle if less than 60°. 相似文献
18.
We have considered the transport equation for radiative transfer to a problem in semi-infinite atmosphere with no incident radiation and scattering according to planetary phase function w(1 + xcos ). Using Laplace transform and the Wiener-Hopf technique, we have determined the emergent intensity and the intensity at any optical depth. The emergent intensity is in agreement with that of Chandrasekhar (1960). 相似文献
19.
Solar radiation is the primary energy source for many processes in Earth's environment and is responsible for driving the
atmospheric and oceanic circulation. The integrated strength and spectral distribution of solar radiation is modified from
the space-based {Solar {Radiation and {Climate (SORCE) measurements through scattering and absorption processes in the atmosphere
and at the surface. Understanding how these processes perturb the distribution of radiative flux density is essential in determining
the climate response to changes in concentration of various gases and aerosol particles from natural and anthropogenic sources,
as is discerning their associated feedback mechanisms. The past decade has been witness to a tremendous effort to quantify
the absorption of solar radiation by clouds and aerosol particles via airborne and space-based observations. Vastly improved
measurement and modeling capabilities have enhanced our ability to quantify the radiative energy budget, yet gaps persist
in our knowledge of some fundamental variables. This paper reviews some of the many advances in atmospheric solar radiative
transfer as well as those areas where large uncertainties remain. The SORCE mission's primary contribution to the energy budget
studies is the specification of the solar total and spectral irradiance at the top of the atmosphere. 相似文献
20.
To evalute the effect of the non-uniform surface on the radiation field, the upwelling radiation at the top of the atmosphere bounded by the checkerboard type of terrain is computed using the modified doubling method. The terrain is composed of the square Lambert surfaces with two different albedoes. The dimension of the each square is assumed to be 0.5–6 km. The radiance of the terrain is discussed with respect to the atmospheric effect. The observational site is located at altitude 30 km. The corresponding projected point on the ground is located at the center of a square. The solar and observational direction is located in the plane parallel to the checkerboard squares. The atmosphere is assumed to be homogeneous, which is composed of aerosol and molecules, where the model aerosol is of the oceanic or the water soluble types.Numerical simulation exhibits the extraordinary effect near the edge of each squares. The radiance of the terrain depends upon the difference of albedoes and size of squares. It increases with the increase of the dimension of the square. It decreases with the optical thickness. At large optical thickness, the variation of radiation with zenith direction depends upon the aerosol characteristics. It shows little dependence on the solar zenith angle if less than 20°. 相似文献