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Results for “ATMOSPHERIC ABSORPTION”

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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

After long arduous work with the simulator, measurements of the refractivity and absorptivity of nitrogen under conditions similar to those for Titan were completed. The most significant measurements, however, were those of the microwave absorption from gaseous ammonia under simulated conditions for the Jovian atmospheres over wavelengths from 1.3 to 22 cm. The results of these measurements are critical in that they confirm the theoretical calculation of the ammonia opacity using the Ben-Reuven lineshape. The application of both these results, and results obtained previously, to planetary observations at microwave frequencies were especially rewarding. Applications of the results for ammonia to radio astronomical observations of Jupiter in the 1.3 to 20 cm wavelength range and the application of results for gaseous H2SO4 under simulated Venus conditions are discussed.

Steffes, P. G.↗
NASA NTRS1971

Infrared Absorption of Carbon Dioxide at High Densities With Application to the Atmosphere of Venus

Several new infrared absorptions were found in carbon dioxide. All are normally forbidden, and were collision-induced in an absorbing cell whose combination of pressure and path length has a unique sensitivity for induced absorptions. The new absorptions in the 2.3 micron region are attributed to transitions from ground to the 3(1)1 Fermi pair at 4248 and 4391/cm. Other absorptions are attributed to simultaneous CO2-N2 transitions and to the 00(0)0-00(0)2 transition in CO2 polarizability derivatives and regular progressions in strength versus increasing quantum number. The spectra were used to predict the radiative transfer in a dry CO2 model of the lower Venus atmosphere. The results indicate that the radiation balance in the lower atmosphere is adequately explained by a dry massive atmosphere of CO2 with a layer of infrared-opaque clouds. The absorptions in the 2.3 micron region are significant in accounting for the opacity to sustain Venus' 768 K surface temperature.

John Fitzallen Moore↗
NASA NTRS1974

Remote atmospheric sensing with an airborne laser absorption spectrometer

A laser absorption spectrometer, using an infrared laser transmitter and a heterodyne radiometer, can be used from an aircraft or spacecraft to measure altitude profiles of air pollutants and other atmospheric constituents. The technique involves measurement of differential absorption at several wavelengths, using the diffusely reflecting earth's surface to provide a return signal. The pressure broadening of absorption lines allows one to discriminate between high and low altitude absorbers. Application of the technique to measurements of ozone, nitric oxide, and water vapor are presented. CO2 and CO lasers are considered as transmitters. The discussion includes altitude resolution limitations, atmospheric temperature dependence, and frequency stability requirements of the instrument.

Menzies, R. T.↗
NASA NTRS1974

Remote atmospheric sensing with an airborne laser absorption spectrometer

A laser absorption spectrometer, using an IR laser transmitter and a heterodyne radiometer, can be used from an aircraft or spacecraft to measure altitude profiles of air pollutants and other atmospheric constituents. The technique involves measurement of differential absorption at several wavelengths, using the diffusely reflecting earth's surface to provide a return signal. The pressure broadening of absorption lines allows one to discriminate between high and low altitude absorbers. Application of the technique to measurements of ozone, nitric oxide, and water vapor are presented. CO2 and CO lasers are considered as transmitters. The discussion includes altitude resolution limitations, atmospheric temperature dependence, and frequency stability requirements of the instrument.

Menzies, R. T.↗
NASA NTRS1990

Laboratory measurements and modeling of microwave absorption by ammonia in gas mixtures applicable to giant planet atmospheres

Accurate knowledge of the microwave absorption behavior of ammonia is critical to the correct interpretation of radio astronomical and radio occultation data from the giant planets. New cavity resonator techniques developed at the Stanford Center for Radar Astronomy have allowed accurate laboratory measurements of the microwave absorptivity and refractivity spectra of gas mixtures containing trace amounts of ammonia. A parameterized version of the modified Ben-Reuven formalism of Berge and Bulkis was optimized to fit the new data. The new formalism produced by this method predicts ammonia absorptivity much more accurately than previous formalism over a significant range of conditions.

Spilker, T. R.↗
NASA NTRS1984

The absorption of solar radiation by the Arctic atmosphere during the haze season and its effects on the radiation balance

Measurements of broadband spectral absorption of solar radiation by the Arctic atmosphere during haze events are reported. A preliminary analysis of the data indicates that large changes occur in the radiative transfer processes in the Arctic during haze events. For example, the planetary albedo is estimated to increase by 2.5 percent over the ocean and to decrease by 9 percent over the ice cap. Changes of such magnitude in the radiative parameters have the potential for significant climatic effects. The need for further experimental and modeling efforts is emphasized.

Valero, F. P. J.↗
NASA NTRS1994

Spectroscopy of Mars form 2.04 to 2.44 micron during the 1993 opposition: Absolute calibration and atmospheric vs mineralogic origin of narrow absorption features

We present moderate-resolution (lambda/delta lambda = 300 to 370) reflectance spectral of Mars from 2.04 to 2.44 microns that were obtained at United Kingdom Infrared Telescope (UKIRT) during the 1993 opposition. Seven narrow absorption features were detected and found to have a Mars origin. By comparison with solar and Mars atmospheric spectra, five of these features were attributed all or in part to Mars atmospheric CO2 or CO (2.052 +/- 0.003, 2.114 +/- 0.002, 2.150 +/- 0.003, 2.331 +/- 0.001, and 2.357 +/- 0.002 microns). Two of the bands (2.331 +/- 0.001 and 2.357 +/- 0.002 micron) appear to have widths and depths that are consistent with additional, nonatmospheric absorptions, although a solar contribution cannot be entirely ruled out. Two other weak bands centered at 2.278 +/- 0.002 and 2.296 +/- 0.002 microns may be at least partially mineralogic in origin. The data provide no conclusive identification of the mineralogy responsible for these absorption features. However, examination of terrestrial spectral libraries and previous mineralogy responsible for these absorption features. However, examination of terrestrial spectral libraires and previous moderate spectral resolution mineral studies indicates that the most likely origin of these features is either (bi)carbonate or (bi)sulfate anions in framework silicates of (Fe, Mg)-OH bonds in sheet silicates. If the bands are caused by phyllosilicate minerals, then an explanation must be found for the extremely narrow widths of the cation-OH features in the Mars spectra as compared to terrestrial minerals.

Bell, James F., III↗
NASA NTRS1994

Spectroscopy of Mars from 2.04 to 2.44 micrometers during the 1993 opposition: absolute calibration and atmospheric vs mineralogic origin of narrow absorption features

We present moderate-resolution (lambda/delta lambda = 300 to 370) reflectance spectra of Mars from 2.04 to 2.44 micrometers that were obtained at UKIRT during the 1993 opposition. Seven narrow absorption features were detected and found to have a Mars origin. By comparison with solar and Mars atmospheric spectra, five of these features were attributed all or in part to Mars atmospheric CO2 or CO(2.052 +/- 0.003, 2.114 +/- 0.002, 2.150 +/- 0.003, 2.331 +/- 0.001, and 2.357 +/- 0.002 micrometers). Two of the bands (2.331 +/- 0.001 and 2.357 +/- 0.002 micrometers) appear to have widths and depths that are consistent with additional, nonatmospheric absorptions, although a solar contribution cannot be entirely ruled out. Two other weak bands centered at 2.278 +/- 0.002 and 2.296 +/- 0.002 micrometers may be at least partially mineralogic in origin. The data provide no conclusive identification of the mineralogy responsible for these absorption features. However, examination of terrestrial spectral libraries and previous moderate spectral resolution mineral studies indicates that the most likely origin of these features is either (bi)carbonate or (bi)sulfate anions in framework silicates or (Fe, Mg)-OH bonds in sheet silicates. If the bands are caused by phyllosilicate minerals, then an explanation must be found for the extremely narrow widths of the cation-OH features in the Mars spectra as compared to terrestrial minerals.

Mars↗
NASA NTRS1983

A radiative transfer model for surface radiation budget studies

A high resolution spectral radiative transfer model of the troposphere for computing downwelling radiance and flux density at the surface in the 5-200 micron region has been developed. The model is fast and accurate and takes into consideration all major and minor constituents active in this region, namely, water vapor, carbon dioxide, ozone, nitrous oxide, and methane. It uses the quasi-random band model of absorption for computing atmospheric transmittances due to various bands. Continuum absorption by water vapor in the 8-14 micron region has also been taken into account. The model has been used to examine the sensitivity of downwelling flux to variations of surface water vapor pressure (or surface relative humidity), water vapor scale-height and concentrations of other gaseous constituents of the atmosphere. In addition, sensitivity to changes in a number of cloud parameters, namely, fractional cloud cover, cloud height, and high-cloud emissivity, has also been examined. Results obtained with the present model compare well with those from the empirical and semi-empirical correlations. The present work demonstrates, for the first time, the feasibility of using a high-resolution narrow-band model for computing this flux for a meteorological application.

Gupta, S. K.↗
NASA NTRS1973

On ultraviolet absorption by molecular hydrogen in stellar atmospheres.

The total LTE opacity expected for a variety of temperatures and pressures has been calculated for a mixture of solar composition. The absorption coefficient for the H2 singlet transition between 1300 and 2000 A was obtained from computations at 5000 K by Sando and Dalgarno (1971). It is found that a correct estimate of the resonance broadening in Lyman-alpha wings leads to important modifications of the UV opacity.

Praderie, F.↗
NASA NTRS1996

Laboratory Measurement of the Temperature Dependence of Gaseous Sulfur Dioxide (SO2) Microwave Absorption with Application to the Venus Atmosphere

High-accuracy laboratory measurements of the temperature dependence of the opacity from gaseous sulfur dioxide (SO2) in a carbon dioxide (CO2) atmosphere at temperatures from 290 to 505 K and at pressures from 1 to 4 atm have been conducted at frequencies of 2.25 GHz (13.3 cm), 8.5 GHz (3.5 cm), and 21.7 GHz (1.4 cm). Based on these absorptivity measurements, a Ben-Reuven (BR) line shape model has been developed that provides a more accurate characterization of the microwave absorption of gaseous S02 in the Venus atmosphere as compared with other formalisms. The developed BR formalism is incorporated into a radiative transfer model. The resulting microwave emission spectrum of Venus is then used to set an upper limit on the disk-averaged abundance of gaseous S02 below the main cloud layer. It is found that gaseous S02 has an upper limit of 150 ppm, which compares well with previous spacecraft in situ measurements and Earth-based radio astronomical observations.

Suleiman, Shady H.↗
NASA NTRS2012

Airborne Lidar Measurements of Atmospheric Pressure Made Using the Oxygen A-Band

Accurate measurements of greenhouse gas mixing ratios on a global scale are currently needed to gain a better understanding of climate change and its possible impact on our planet. In order to remotely measure greenhouse gas concentrations in the atmosphere with regard to dry air, the air number density in the atmosphere is also needed in deriving the greenhouse gas concentrations. Since oxygen is stable and uniformly mixed in the atmosphere at 20.95%, the measurement of an oxygen absorption in the atmosphere can be used to infer the dry air density and used to calculate the dry air mixing ratio of a greenhouse gas, such as carbon dioxide or methane. OUT technique of measuring Oxygen uses integrated path differential absorption (IPDA) with an Erbium Doped Fiber Amplifier (EDF A) laser system and single photon counting module (SPCM). It measures the absorbance of several on- and off-line wavelengths tuned to an O2 absorption line in the A-band at 764.7 nm. The choice of wavelengths allows us to maximize the pressure sensitivity using the trough between two absorptions in the Oxygen A-band. Our retrieval algorithm uses ancillary meteorological and aircraft altitude information to fit the experimentally obtained lidar O2 line shapes to a model atmosphere and derives the pressure from the profiles of the two lines. We have demonstrated O2 measurements from the ground and from an airborne platform. In this paper we will report on our airborne measurements during our 2011 campaign for the ASCENDS program.

Riris, Haris↗
NASA NTRS1992

Absorption coefficients of CFC-11 and CFC-12 needed for atmospheric remote sensing and global warming studies

Spectral absorption coefficients k(v) in the atmospheric window are reported for CFC-11 and CFC-12. Data obtained with a grating spectrometer are compared with NCAR cross sections and measurements of k(v) made with a tunable diode laser spectrometer at various temperature-pressure combinations representing tangent heights or layers in the atmosphere are presented. The results are suitable for atmospheric remote sensing and global warming studies.

Varanasi, Prasad↗
NASA NTRS1983

Determination of atmospheric properties from lidar measurements

Differential absorption lidar techniques for determining basic atmospheric properties to high accuracy are described. The theory of a two-wavelength lidar temperature measurement is given with simulation results that show accuracies of 0.5 to 1 K for measurements from ground-based and satellite platforms. The theory of measurements of the atmospheric pressure profile using absorption troughs, broad regions of nearly uniform absorption, is also described with simulation results that show accuracies of 0.1 to 0.3 percent. Recent measurements which confirm the accuracy of these techniques are reviewed.

Korb, C. L.↗
NASA NTRS2013

NF3: UV Absorption Spectrum Temperature Dependence and the Atmospheric and Climate Forcing Implications

Nitrogen trifluoride (NF3) is an atmospherically persistent greenhouse gas that is primarily removed by UV photolysis and reaction with O((sup 1)D) atoms. In this work, the NF3 gas-phase UV absorption spectrum, sigma(delta,T), was measured at 16 wavelengths between 184.95 and 250 nm at temperatures between 212 and 296 K. A significant spectrum temperature dependence was observed in the wavelength region most relevant to atmospheric photolysis (200-220 nm) with a decrease in sigma(210 nm,T) of approximately 45 percent between 296 and 212 K. Atmospheric photolysis rates and global annually averaged lifetimes of NF3 were calculated using the Goddard Space Flight Center 2-D model and the sigma(delta,T) parameterization developed in this work. Including the UV absorption spectrum temperature dependence increased the stratospheric photolysis lifetime from 610 to 762 years and the total global lifetime from 484 to 585 years; the NF3 global warming potentials on the 20-, 100-, and 500-year time horizons increased less than 0.3, 1.1, and 6.5 percent to 13,300, 17,700, and 19,700, respectively.

nitrogen trifluoride↗
NASA NTRS1980

Investigation of infrared spectra of atmospheric gases to support stratospheric spectroscopic investigations

Spectroscopic instrumentation and the absorption characteristics of atmospheric gases are discussed in relation to the requirements of spectroscopic stratospheric experiments. Improvement in the spectral resolution, accuracy of the line parameters, and the ranges of atmospheric conditions over which information is to be obtained are among the factors considered. Methods of simultaneously analyzing entire bands containing many lines were developed and applied to the analysis of bands of N20 and CO2. Progress in this analysis is reported.

Shaw, J. H.↗
NASA NTRS1984

Spectral absorption of solar radiation in cloudy atmospheres A 20/cm model

A radiative transfer model based on both LOWTRAN transmission functions (at a 20/cm resolution), and Monte Carlo simulations of wavelength distributions, is used to determine the spectral absorption of solar radiation in typical water clouds. This yields the relative absorption by the vapor and droplets within each cloud. The results obtained indicate a slightly lower absorption than had previously been found, with boundary layer clouds typically absorbing 9 percent of the terrestrial insolation for an overhead sun. This absorption is strongly dependent on the presence of water vapor above the cloud top and solar zenith angle. Droplets, rather than vapor, are shown to be the dominant absorbers within the cloud except in the absence of water vapor above the cloud top.

Davies, R.↗