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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
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NASA NTRS1981

An efficient method for computing the absorption of solar radiation by water vapor

Chou and Arking (1980) have developed a fast but accurate method for computing the IR cooling rate due to water vapor. Using a similar approach, the considered investigation develops a method for computing the heating rates due to the absorption of solar radiation by water vapor in the wavelength range from 4 to 8.3 micrometers. The validity of the method is verified by comparison with line-by-line calculations. An outline is provided of an efficient method for transmittance and flux computations based upon actual line parameters. High speed is achieved by employing a one-parameter scaling approximation to convert an inhomogeneous path into an equivalent homogeneous path at suitably chosen reference conditions.

Chou, M.-D.↗
NASA NTRS1971

Large-scale reflection and absorption of solar radiation by clouds as influencing earth radiation budgets - New aircraft measurements.

Discussion of the first results of extensive recent aircraft measurements, in the short wavelengths, of the reflection and absorption properties of clouds and their impact on radiation budget studies. From the data obtained, the albedo of typical cloud types was determined integrally and spectrally. Some preliminary results are also offered for short-wave absorption and the apparent transmission of clouds. The effect of the atmospheric pathlength between sensor and target, exhibited through molecular scattering and aerosol scattering and absorption, is included in the data analysis. Results are also presented on vertical (short-wave) radiative flux profiles, within specific wavelength intervals, from near sea level to altitudes of about 40,000 ft over relatively short time intervals.

Drummond, A. J.↗
NASA NTRS1974

Mechanisms for the emission and absorption of gravitational radiation

Following some introductory comments on the fundamentals or first principles governing jointly the emission and absorption of gravitational waves, a list is given of observational targets or goals for gravitational wave astronomy which have been selected from recent critical reviews. Then theoretical studies of plunge radiation and gravitational synchrotron radiation are surveyed, since in this area new techniques are developing rapidly although new observational prospects have not yet been found.

Misner, C. W.↗
NASA NTRS1994

Comparison of daily averaged reflection, transmission, and absorption for selected radiative flux transfer approximations

This paper compares accuracy for the daily averaged reflection, transmission, and absorption of solar flux derived from the delta-four-stream approximation and a few selected two-stream approximations. In the chosen variety of two-stream approximations, a two-stream approximation suggested by Zhu produces the most accurate reflection and transmission for conservative scattering with optical thickness tau(sub 1) less than 3. Otherwise, the delta-Eddington approximation is superior to other two-stream approximations. The delta-four stream approximation produces errors that are smaller than the delta-Eddington approximation by at least a factor of 2.

Zhu, Xun↗
NASA NTRS1974

Free-free absorption of infrared radiation in collisions of electrons with neutral rare-gas atoms

A relationship between the inverse bremsstrahlung absorption cross section and the electron neutral momentum transfer cross section has been utilized to determine the infrared free-free continuum absorption coefficient for the negative ions of helium, neon, argon, krypton, and xenon. The values of the momentum transfer cross section for this calculation have been obtained from experimental measurements. Analytical expressions for the absorption coefficient have also been developed. From the results of this calculation, it is possible to determine the absorption coefficient per unit electron density per neutral atom for temperatures in the range from 2500 to 25,000 K. The results are compared with those from tabulations of previous calculations and those computed from theoretical values of the phase shifts for the elastic scattering of electrons by neutral atoms.

Stallcop, J. R.↗
NASA NTRS1993

Absorption of solar radiation by O2 - Implications for O3 and lifetimes of N2O, CFCl3, and CF2Cl2

An accurate line-by-line model is used to evaluate effects of absorption in the Schumann-Runge bands of O2 on transmission of UV radiation. The model is used to evaluate rates of photolysis for N2O, CFCl3, and CF2Cl2, and to infer global loss rates and instantaneous lifetimes appropriate for 1980. A parameterized version of the line-by-line model enabling rapid evaluation of transmission in the Schumann-Runge region is described. Photochemical calculations employing the parameterization and constrained by data from the Atmospheric Trace Molecule Spectroscopy experiment are used to examine the budget of odd oxygen. Consistent with previous studies, it is shown that photochemical loss of odd oxygen exceeds production by photolysis of O2 for altitudes above 40 km. The imbalance between production and loss is shown to be consistent with a source of odd oxygen proportional to the product of the mixing ratio and photolysis rate of ozone, which suggests that processes involving vibrationally excited O2 may play an important role in production of odd oxygen.

Minschwaner, K.↗
NASA NTRS1988

Pressure-induced absorption coefficients for radiative transfer calculations in Titan's atmosphere

The semiempirical theory of Birnbaum and Cohen (1976) is used to calculate the FIR pressure-induced absorption (PIA) spectra of N2, CH4, N2 + Ar, N2 + CH4, and N2 + H2 under conditions like those in the Titan troposphere. The results are presented graphically and compared with published data from laboratory measurements of PIA in the same gases and mixtures (Dagg et al., 1986; Dore et al., 1986). Good agreement is obtained, with only a slight underestimation of PIA at 300-400/cm in the case of CH4. The absorption coefficients are presented in tables, and it is suggested that the present findings are of value for evaluating the effects of tropospheric clouds on the Titan FIR spectrum and studying the greenhouse effect near the Titan surface.

Courtin, Regis↗
NASA NTRS1975

Empirical evidence concerning absorption lines and radiation pressure in quasi-stellar objects

Empirical spectroscopic evidence is examined for the hypothesis that radiation pressure having large gradients with wavelength plays a crucial role in maintaining patterns of redshift differences in quasars. Seventy-four absorption-line redshift systems in 32 quasars and two Seyfert galaxies are analyzed and discussed in terms of the radiation-pressure line-locking hypothesis. Redshift line ratios greater than unity are computed for each quasar and plotted as histograms. Ratios which may indicate line and edge locking are identified, including those of the C IV and Mg II doublets and those of the N III/C III, He II/O III, C II/He I, Ly-beta/H I, and H I/He I ionization edges.

Burbidge, E. M.↗
NASA NTRS1981

Absorption of visible radiation by aerosols in the volcanic plume of Mount St. Helens

Samples of particles from Mount St. Helens were collected in both the stratosphere and troposphere for measurement of the light absorption coefficient. Results indicate that the stratospheric dust had a small but finite absorption coefficient ranging up to 2 x 10 to the minus 7 per meter at a wavelength of 0.55 micron, which is estimated to yield an albedo for single scatter of 0.98 or greater. Tropospheric results showed similar high values of an albedo for single scatter

Ogren, J. A.↗
NASA NTRS1986

Comparative accuracy of the Albedo, transmission and absorption for selected radiative transfer approximations

Illustrations of both the relative and absolute accuracy of eight different radiative transfer approximations as a function of optical thickness, solar zenith angle and single scattering albedo are given. Computational results for the plane albedo, total transmission and fractional absorption were obtained for plane-parallel atmospheres composed of cloud particles. These computations, which were obtained using the doubling method, are compared with comparable results obtained using selected radiative transfer approximations. Comparisons were made between asymptotic theory for thick layers and the following widely used two stream approximations: Coakley-Chylek's models 1 and 2, Meador-Weaver, Eddington, delta-Eddington, PIFM and delta-discrete ordinates.

King, M. D.↗
NASA NTRS1974

A parameterization for the absorption of solar radiation in the earth's atmosphere

A method is described for rapidly computing the amount of solar energy absorbed at the earth's surface and in the atmosphere as a function of altitude. The method is a parametric treatment, but the form of the solution and the coefficients involved are based on accurate multiple-scattering computations. In this treatment the absorption varies with the amount and type of clouds, the humidity, the zenith angle of the sun, and the albedo of the earth's surface. Within the stratosphere the absorption also depends on the vertical distribution of ozone. This parameterization for solar radiation is being used in current versions of the global atmospheric circulation model developed at the Goddard Institute for Space Studies.

Lacis, A. A.↗
NASA NTRS1998

Absorption of Solar Radiation by the Cloudy Atmosphere: Further Interpretations of Collocated Aircraft Measurements

We have extended the interpretations made in two prior studies of the aircraft shortwave radiation measurements that were obtained as part of the Atmospheric Radiation Measurements (ARM) Enhanced Shortwave Experiments (ARESE). These extended interpretations use the 500 nm (10 nm bandwidth) measurements to minimize sampling errors in the broadband measurements. It is indicated that the clouds present during this experiment absorb more shortwave radiation than predicted by clear skies and thus by theoretical models, that at least some (less than or equal to 20%) of this enhanced cloud absorption occurs at wavelengths less than 680 nm, and that the observed cloud absorption does not appear to be an artifact of sampling errors nor of instrument calibration errors.

Cess, R. D.↗
NASA NTRS1980

Tunable diode laser heterodyne radiometer measurement of atmospheric absorption of solar radiation

A tunable infrared heterodyne radiometer (TIHR) which uses a diode laser as the local oscillator is described as well as methods for the evaluation of the excess noise characteristics of the tunable diode laser. Preliminary atmospheric absorption data taken with the TIHR are presented and show the capability of the TIHR for making the highest resolution atmospheric measurements to date.

Harward, C. N.↗
NASA NTRS1983

Parameterization of cloud effects on the absorption of solar radiation

A radiation parameterization for the NASA Goddard climate model was developed, tested, and implemented. Interactive and off-hire experiments with the climate model to determine the limitations of the present parameterization scheme are summarized. The parameterization of Cloud absorption in terms of solar zeith angle, column water vapors about the cloud top, and cloud liquid water content is discussed.

Davies, R.↗
NASA NTRS1980

An Accurate Method for Computing the Absorption of Solar Radiation by Water Vapor

The method is based upon molecular line parameters and makes use of a far wing scaling approximation and k distribution approach previously applied to the computation of the infrared cooling rate due to water vapor. Taking into account the wave number dependence of the incident solar flux, the solar heating rate is computed for the entire water vapor spectrum and for individual absorption bands. The accuracy of the method is tested against line by line calculations. The method introduces a maximum error of 0.06 C/day. The method has the additional advantage over previous methods in that it can be applied to any portion of the spectral region containing the water vapor bands. The integrated absorptances and line intensities computed from the molecular line parameters were compared with laboratory measurements. The comparison reveals that, among the three different sources, absorptance is the largest for the laboratory measurements.

Chou, M. D.↗
NASA NTRS1994

On the polarization of resonantly scattered emission lines - 1. Emission and absorption coefficients in an anisotropic radiation field

Source functions and absorptions coefficients for polarized radiation in a given ansiotropic radiation field are calculated for a variety of permitted electric dipole transitions in the L-S coupling limit. Collisional, radiative and magnetic mixing of the ground sublevels are all considered. The polarization of the self-consistent, emergent radiation field is computed, using an anisotropic escape probability formalism to treat the radiative transfer. It is found that the radiative mixing can enhance the polarization for transitions with large angular momentum, and degrees of polarization less than or approximately 10 per cent are obtained for transitions with small angular momentum.

Lee, H. -W.↗