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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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NASA NTRS1973

The Nimbus 4 infrared spectroscopy experiment. 2: Comparison of observed and theoretical radiance from 425-1450 cm(minus 1)

The Nimbus 4 infrared interferometer spectrometer (IRIS) measured the thermal emission of the earth's atmosphere and surface from 400-1600/cm with an apodized spectral resolution of 2.8/cm. A comparison of theoretical radiances, computed from in-situ measurements and using a direct integration slant path atmospheric transmittance model, with the observed IRIS radiances has been made to verify the radiometeric and spectral performance of the instrument and to assess the accuracy of the atmospheric transmittances. The radiance comparison has indicated a relatively constant difference of less than 5% in the water vapor continuum in the 425-550/cm and 750-1200/cm atmospheric window regions while in the 667/cm CO2 band the difference was 5-10%. The absolute accuracy was found to be approximately 5-10% for each of the parameters; measured radiances, in-situ measurements, and the atmospheric transmittances, thus it is not possible to uniquely specify the degree of error arising from each parameter in the total resultant difference.

Kunde, V. G.↗
NASA NTRS1974

The Nimbus 4 infrared spectroscopy experiment. II - Comparison of observed and theoretical radiances from 425-1450 wavelengths/cm

The Nimbus 4 infrared interferometer spectrometer (IRIS) measured the thermal emission of the earth's atmosphere and surface from 400-1600 wavelengths/cm with an apodized spectral resolution of 2.8 wavelengths/cm. A comparison of theoretical radiances, computed from in situ measurements and using a direct integration slant path atmospheric transmittance model, with the observed IRIS radiances has been made to verify the radiometric and spectral performance of the instrument and to assess the accuracy of the atmospheric transmittances. The radiance comparison has indicated a relatively constant difference of less than 5% in the water vapor continuum in the 425 to 550 wavelengths/cm and 750 to 1200 wavelengths/cm atmospheric 'window' regions, whereas in the 667 wavelengths/cm CO2 band the difference was 5-10%.

Kunde, V. G.↗
NASA NTRS1974

Nimbus 4 IRIS spectra in the 750-1250 wavelengths/cm atmospheric window region

Present operational schemes for infrared remote sounding measurements of surface temperature use the 899 wavelengths/cm atmospheric window region. Spectra from the Nimbus 4 IRIS in the 750 to 1250 wavelengths/cm region are analyzed. Comparison of the actual surface temperature and the observed brightness temperature at 10 wavelengths/cm resolution shows that the clearest windows were at 936 and 960 wavelengths/cm. Although there is a small amount of CO2 absorption in these regions, this is compensated for by a decrease in water vapor continuum absorption. Atmospheric absorption was 0.5 K less than experienced by the 899 wavelengths/cm window.

Kunde, V. G.↗
NASA NTRS1978

Effect of tropospheric aerosols upon atmospheric infrared cooling rates

An investigation has been made of the impact of wind-blown dust particles upon local climate of arid regions. The case of Northwest India is specifically considered, where a dense layer of dust persists for several months during the summer. In order to examine the effect of this dust layer on the infrared radiative flux and cooling rates, a method is presented for calculating the IR flux within a dusty atmosphere which allows the use of gaseous band models and is applicable in the limit of small single scattering albedo and pronounced forward scattering. The participating components of the atmosphere are assumed to be water vapor and spherical quartz particles only. The atmospheric window is partially filled by including the water vapor continuum bands for which empirically obtained transmission functions have been used. It is shown that radically different conclusions may be drawn on dust effects if the continuum absorption is not considered. The radiative transfer model, when applied to a dusty atmosphere, indicates that there is a moderate enhancement in the atmospheric greenhouse and a 10% increase in the mean IR radiative cooling rate, relative to the dust free case, within the lower troposphere. These results have been compared with previous work by other authors in the context of the possibility of dust layers inhibiting local precipitation.

Harshvardhan, MR.↗
NASA NTRS1985

Preliminary GCM Results with a New Radiation Parameterization

A new parameterization of solar and terrestrial radiation was developed and tested. The solar radiation parameterization is based on that of Lacis and Hansen (1974), but with zenith-angle-dependent surface albedoes, and revised treatments of cloudiness. The terrestrial radiation parameterization is based on the work of Chou (1984) for water vapor, Chou and Peng (1983) for carbon dioxide, and Rogers (1968) for ozone, with a new parameterization of the effects of clouds. Results obtained were compared with the new parameterizations to those obtained with the earlier parameterization described by Schlessinger (1976). Several dramatic improvements came to light. For the most part these are related to the fact that the new terrestrial radiation paramerization includes the effects of the water vapor continuum, while the earlier parameterization does not. In the moist tropical planetary boundary layer (PBL) continuum emission leads to much stronger cooling of the PBL over the oceans. Over land, however, the cooling of the PBL is significantly reduced. The latter, somewhat paradoxical result is due to the strong diurnal cycle of the continental PBL. At night the shallow continental PBL is overlain by a moist layer created by mixing during the previous afternoon. The moist upper layer acts as a radiative blanket, reducing the time-averaged radiative cooling of the continental PBL.

Randall, D.↗
NASA NTRS1989

Earth radiation budget and cloudiness simulations with a general circulation model

A GCM with new parameterizations of solar and terrestrial radiation, parameterized cloud optical properties, and a simple representation of the cloud liquid water feedback is used with several observational data sets to analyze the effects of cloudiness on the earth's radiation budget. The January and July results from the model are in reasonable agreement with data from Nimbus-7. It is found that the simulated cloudiness overpredicts subtropical and midlatitude cloudiness. The simulated atmospheric cloud radiative forcing is examined. The clear-sky radiation fields obtained by two methods of Cess and Potter (1987) are compared. Also, a numerical experiment was performed to determine the effects of the water vapor continuum on the model results.

HARSHVARDHAN↗
NASA NTRS1990

Analysis of cirrus optical properties with data from NASA ER2 High-resolution Interferometer Sounder (HIS)

The 8 to 13 micron spectral region is an important atmospheric window for radiometric studies of the Earth's surface and clouds. Most of the Earth-atmosphere longwave radiative loss to space occurs in this spectral region. Selective gaseous absorption in this window occurs in the 9.6 micron ozone band with the remaining absorption dominated by the water vapor continuum. Cirrus clouds have a large impact on the transmittance of this atmospheric window region; it is therefore important to understand the interaction of cirrus cloud with the radiation field for climate studies and in the interpretation of satellite radiometric measurements. The focus was to employ observations of the High-resolution Interferometer Sounder (HIS) made during First ISCCP Regional Experiment (FIRE) to improve the understanding of the radiative properties of cirrus clouds within this window region. Studies were undertaken to investigate the coupling between the microphysical properties of cirrus clouds and their spectral variation within this window region. Extensions of the HIS studies to satellite measurements, with regards to remote sensing and interpretation, were also investigated.

Smith, William L.↗
NASA NTRS1991

Computation of atmospheric cooling rates by exact and approximate methods

Infrared fluxes and cooling rates for several standard model atmospheres, with and without water vapor, carbon dioxide, and ozone, have been calculated using a line-by-line method at 0.01/cm resolution. The sensitivity of the results to the vertical integration scheme and to the model for water vapor continuum absorption is shown. Comparison with similar calculations performed at NOAA/GFDL shows agreement to within 0.5 W/sq m in fluxes at various levels and 0.05 K/d in cooling rates. Comparison with a fast, parameterized radiation code used in climate models reveals a worst case difference, when all gases are included, of 3.7 W/sq m in flux; cooling rate differences are 0.1 K/d or less when integrated over a substantial layer with point differences as large as 0.3 K/d.

Ridgway, William L.↗
NASA NTRS1992

A far wing line shape theory and its application to the water vibrational bands (II)

Attention is given to a far wing line shape theory based on binary collision and quasi-static approximations. The theory is applicable for both the LF and HF wings of vibrational-rotational bands. It is used to calculate the frequency and temperature dependence of the continuous absorption coefficient for frequencies up to 10,000/cm for pure water vapor. The results are compared with existing laboratory data in the 2400-2700/cm window and in the 3000-4300/cm band center region, with field measurements in the 2000-2225/cm region and with a recent experimental measurement near 9466/cm. It is concluded that both the magnitude and temperature dependence of the water vapor continuum can be accounted for by the present theory without the introduction of any adjustable parameters. Refinements of the theory and extension to foreign-broadened absorption are also discussed.

Ma, Q.↗
NASA NTRS1994

Development of practical multiband algorithms for estimating land-surface temperature from EOS/MODIS data

A practical multiband, hierarchical algorithm for estimating land-surface temperature from NASA's future Earth Observing System (EOS) instruments Moderate Resolution Imaging Spectroradiometer (MODIS) and Advance Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is developed through comprehensive, accurate, radiative transfer simulations at moderate spectral steps of 1-5/cm for wide ranges of atmospheric and surface conditions. The algorithm will accept empirical or estimated information about the surface emissivity and reflectivity and the atmospheric temperature and water-vapor profiles. Ground-based and aircraft measurements are necessary to validate and improve the algorithm and to establish its quality. Its accuracy depends on the calibration accuracy of thermal infrared data, uncertainties in surface heterogeneity, and temperature-dependent atmospheric absorption coefficients. Better knowledge of land-surface spectral emissivities and more accurate coefficients for atmospheric molecular band absorption and water vapor continuum absorption are needed to develop global land-surface temperature algorithms accurate to 1-2 K.

Dozier, J.↗
NASA NTRS1998

Measurements of the Downward Longwave Radiation Spectrum over the Antarctic Plateau and Comparisons with a Line-by-Line Radiative Transfer Model for Clear Skies

A 1-year field program was conducted at South Pole Station in 1992 to measure the downward infrared radiance spectrum at a resolution of 1/ cm over the spectral range 550-1667 cm-'. The atmosphere over the Antarctic Plateau is the coldest and driest on Earth, where in winter, surface temperatures average about -60 C, the total column water vapor is as low as 300 pm of precipitable water, and the clear-sky downward longwave flux is usually less than 80 W/sq m. Three clear-sky test cases are selected, one each for summer, winter, and spring, for which high- quality radiance data are available.as well as ancillary data to construct model atmospheres from radiosondes, ozonesondes, and other measurements. The model atmospheres are used in conjunction with the line-by-line radiative transfer model (LBLRTM) to compare model calculations with the spectral radiance measurements. The high-resolution calculations of LBLRTM (approx. = 0.001/ cm) are matched to the lower-resolution measurements (1/ cm) by adjusting their spectral resolution and by applying a correction for the finite field of view of the interferometer. In summer the uncertainties in temperature and water vapor profiles dominate the radiance error in the LBLRTM calculations. In winter the uncertainty in viewing zenith angle becomes important as well as the choice of atmospheric levels in the strong near-surface temperature inversion. The spectral radiance calculated for each of the three test cases generally agrees with that measured, to within twice the total estimated radiance error, thus validating LBLRTM to this level of accuracy for Antarctic conditions. However, the discrepancy exceeds twice the estimated error in the gaps between spectral lines in the region 1250-1500/ cm, where emission is dominated by the foreign-broadened water vapor continuum.

Walden, Von P.↗
NASA NTRS2000

Absorption of Solar Radiation by Clouds: An Overview

This talk provides an overview of the subject of absorption of solar radiation by clouds in the earth's atmosphere. The paper summarizes the available evidence which points to disagreements between theoretical and observed values of cloud absorption (and reflections). The importance of these discrepancies, particularly to remote sensing of clouds as well as to studies of cloud physics and earth radiation budgets, is emphasized. Existing cloud absorption and reflection measurements are reviewed and the persistent differences that exist between calculated and measured near-infrared cloud albedos are highlighted. Various explanations for these reflection and absorption discrepancies are discussed under two separate paths: a theoretician's approach and an experimentalist's approach. Examples for the former approach include model accuracy tests, large-droplet hypothesis, excess absorbing aerosol, enhanced water vapor continuum absorption, and effects of cloud inhomogeneity. The latter approach focuses on discussions of instrumental device, calibration, operational strategy, and signal/noise separation. A recommendation for future activities on this subject will be given.

Tsay, Si-Chee↗
NASA NTRS2001

Absorption of Solar Radiation by Clouds: A Second Look at Irradiance Measurements

A decade ago, Stephens and Tsay provided an overview of the subject of absorption of solar radiation by clouds in the earth's atmosphere. They summarized the available evidence that pointed to disagreements between theoretical and observed values of cloud absorption (and reflection). At that time, a theoretician's approach (assuming perfect flux measurements) was adopted to test the model uncertainty under various hypotheses, such as the omitted large drops, excess absorbing aerosols, enhanced water vapor continuum absorption, and cloud inhomogeneity. Since then, several advances in theoretical work have been made, but a satisfactory answer for the discrepancy is still lacking. Now, we offer an experimentalist's approach (focusing on field, not laboratory) to examine the observational uncertainty under numerous field factors, such as the temperature dependence, attitude control, and sampling strategy in the spatial and spectral domain. Examples from recent field campaigns have pointed out that these sources of error may be responsible for the unacceptable level of uncertainty (e.g., as large as 20 W/square m). We give examples of each, discuss their contribution to overall uncertainty in shortwave absorption, and suggest a coordinated approach to their solution.

Tsay, Si-Chee↗
NASA NTRS2004

Design of a Far-Infrared Spectrometer for Atmospheric Thermal Emission Measurements

Global measurements of far infrared emission from the upper troposphere are required to test models of cloud radiative forcing, water vapor continuum emission, and cooling rates. Spectra with adequate resolution can also be used for retrieving atmospheric temperature and humidity profiles, and yet there are few spectrally resolved measurements of outgoing longwave flux at wavelengths longer than 16 m. It has been difficult to make measurements in the far infrared due to the need for liquid-helium cooled detectors and large optics to achieve adequate sensitivity and bandwidth. We review design considerations for infrared Fourier transform spectrometers, including the dependence of system performance on basic system parameters, and discuss the prospects for achieving useful sensitivity from a satellite platform with a lightweight spectrometer using uncooled detectors.

Johnson, David G.↗
NASA NTRS2014

NASA Tech Briefs, January 2014

Topics include: Multi-Source Autonomous Response for Targeting and Monitoring of Volcanic Activity; Software Suite to Support In-Flight Characterization of Remote Sensing Systems; Visual Image Sensor Organ Replacement; Ultra-Wideband, Dual-Polarized, Beam-Steering P-Band Array Antenna; Centering a DDR Strobe in the Middle of a Data Packet; Using a Commercial Ethernet PHY Device in a Radiation Environment; Submerged AUV Charging Station; Habitat Demonstration Unit (HDU) Vertical Cylinder Habitat; Origami-Inspired Folding of Thick, Rigid Panels; A Novel Protocol for Decoating and Permeabilizing Bacterial Spores for Epifluorescent Microscopy; Method and Apparatus for Automated Isolation of Nucleic Acids from Small Cell Samples; Enabling Microliquid Chromatography by Microbead Packing of Microchannels; On-Command Force and Torque Impeding Devices (OC-FTID) Using ERF; Deployable Fresnel Rings; Transition-Edge Hot-Electron Microbolometers for Millimeter and Submillimeter Astrophysics; Spacecraft Trajectory Analysis and Mission Planning Simulation (STAMPS) Software; Cross Support Transfer Service (CSTS) Framework Library; Arbitrary Shape Deformation in CFD Design; Range Safety Flight Elevation Limit Calculation Software; Frequency-Modulated, Continuous-Wave Laser Ranging Using Photon-Counting Detectors; Calculation of Operations Efficiency Factors for Mars Surface Missions; GPU Lossless Hyperspectral Data Compression System; Robust, Optimal Subsonic Airfoil Shapes; Protograph-Based Raptor-Like Codes; Fuzzy Neuron: Method and Hardware Realization; Kalman Filter Input Processor for Boresight Calibration; Organizing Compression of Hyperspectral Imagery to Allow Efficient Parallel Decompression; and Temperature Dependences of Mechanisms Responsible for the Water-Vapor Continuum Absorption.

Source record↗
NASA NTRS1993

The infrared continuum of pure water vapor - Calculations and high-temperature measurements

Results of experimental and theoretical studies of medium infrared absorption by pure water vapor are reported. The experiments were performed in the 1900-2600/cm and 3900-4600/cm regions for temperatures and pressures of 500-900 K and 0-70 atm, respectively. The results are consistent with data in the literature and enable the determination of continuous absorption parameters.

Hartmann, J. M.↗
NASA NTRS1990

Observation of a strong inverse temperature dependence for the opacity of atmospheric water vapor in the mm continuum near 280 GHz

Results are presented of the field measurements of atmospheric opacity at 278 GHz (9.3/cm) conducted at the McMurdo Station (Antarctica) during the austral springs of 1986 and 1987, in conjunction with balloon measurements of water vapor profile and total column density, showing a strong inverse temperature dependence when normalized to precipitable water vapor. The value of measured opacity per mm of precipitable water vapor (PWV) is roughly two times greater at -35 C than at -10 C and three times greater than measurements at +25 C reported by Zammit and Ade (1981). Various theories proposed to explain excess absorption in continuum regions are reviewed.

Emmons, Louisa K.↗
NASA NTRS1992

Raman lidar measurements of water vapor and aerosol/clouds during the FIRE/SPECTRE field campaign

Water vapor is one of the most important constituents of the earth's atmosphere. It has a major impact on both atmospheric dynamics and radiative transfer. From a dynamic standpoint, the distribution of water vapor with height determines convective stability which is the major indicator of destructive storm development. Also, water vapor stored in the planetary boundary layer acts as the fuel to intensify severe weather. In regards to radiative transfer, water vapor is the most active IR molecule in the atmosphere. It is more effective in absorbing and emitting IR radiation than either carbon dioxide or methane, and thus plays an important role in global change. The main objective of FIRE (First ISSCCP (International Satellite Cloud Climatology Project) Regional Experiment) was to study the development and radiative characteristics of cirrus clouds. The SPECTRE (Spectral Radiation Experiment) project was designed to acquire the necessary atmospheric observations to compare radiative measurements with radiative transfer theory, with special emphasis on understanding the water vapor spectral continuum. The FIRE/SPECTRE field campaign was conducted during Nov. - Dec. 1991 in Coffeyville, Kansas. A complete understanding of water vapor, its distribution with height, and its temporal variation was important for both experiments.

Melfi, S. H.↗