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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 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Cloud Properties Derived from Surface-Based Near-Infrared Spectral Transmission

Surface based near-infrared cloud spectral transmission measurements from a recent precipitation/cloud physics field study are used to determine cloud physical properties and relate them to other remote sensing and in situ measurements. Asymptotic formulae provide an effective means of closely approximating the qualitative and quantitative behavior of transmission computed by more laborious detailed methods. Relationships derived from asymptotic formulae are applied to measured transmission spectra to test objectively the internal consistency of data sets acquired during the field program and they confirmed the quality of the measurements. These relationships appear to be very useful in themselves, not merely as a quality control measure, but also a potentially valuable remote-sensing technique in its own right. Additional benefits from this analysis have been the separation of condensed water (cloud) transmission and water vapor transmission and the development of a method to derive cloud liquid water content.

Pilewskie, Peter↗
DOE OSTI2023

Analysis of thermal radiation of a gas-particulate-cloud in a pressurized oxy-coal combustor

Pressurized oxy-combustion (POC) aims to reduce carbon emissions from coal-fired power plants. In the POC process, pulverized coal is burned at elevated pressure in an O2-CO2 environment. The elevated pressure and high CO2 and H2O concentrations strongly impact thermal radiation, thereby significantly distinguishing POC system from conventional atmospheric-pressure air-fired and oxy-fuel combustion. Consequently, a thorough understanding of thermal radiation in POC is required to promote the development of novel combustors. The present computational work analyzes thermal radiation of the gaseous and particle phases in the pilot-scale POC combustor in Washington University in St. Louis. Particularly, the radiation characteristics of the gaseous and particulate cloud were estimated by employing the statistical narrow band model and the large-particle model. It is found that thermal radiation of a particulate cloud dominates in the combustor under the conditions of a furnace temperature of 1500 K and no substantial particle loss. Another important result is that the gas-and-particulate cloud can be approximately treated as a graybody under the same conditions. To be more specific, the results of spectral radiation intensity of a gas comprised of 40% (vol) H2O and 60% CO2 show that when the pressure is increased to 15 bar, and the radiation pathlength to 100 cm, the spectral radiation profile of the gas phase approaches that of a blackbody at the respective temperature. In addition, the emissivity of the particulate cloud has been evaluated as a function of the particle concentration and diameter by means of the large particle model. It is shown that the emissivity grows with the particle concentration but decreases with the particle size for the same mass of a particulate cloud. The emissivity of a particulate cloud in oxy- combustion exceeds that in air-fired combustion. This work could be used to validate the assumption of the gray gas model adopted in numerical simulations.

Li, Lei↗
NASA NTRS1970

Preprocessing of multispectral data and simulation of ERTS data channels to make computer terrain maps of a Yellowstone National Park test site

The possibility of improving the accuracy of terrain classification by preprocessing spectral data was investigated. Terrain maps were made using the following techniques: 1) preprocessing by scan angle function transformation, using the computer-selected best set of three channels; and 2) preprocessing by ratio transformation, using the specified ERTS data channels, simulated by fitting the spectral response of each of the 12 data channels to the ERTS channels by a set of weighting coefficients. By using a simple technique during printout, the maps were produced in color. The normalized scan angle function transformation resulted in the most accurate classification. The best ratio transformation for the Yellowstone Park data was the ratio of each channel to the sum of all channels. A supervised training program involving maximum likelihood decision for selecting the best spectrometer channels and similar techniques for digitizing the data of the analog magnetic tapes were used. Cloud shadows were recognized in addition to eight classes of terrain. Preprocessing of data resulted in more accurate maps, required fewer training areas (hence less preparation and computer time), and enabled much of the area formerly classified as shadow to be reclassified according to actual terrain type.

Smedes, H. W.↗
NASA NTRS1990

Determination of cloud optical depth with the multiple field of view sun photometer

An approach to determining cloud optical depth is presented which utilizes a multiple-field-of-view sun photometer, along with modeled behavior of transmittance ratios as a function of the field of view, to infer the optical depth. The data used in the analysis were collected during the FIRE Stratocumulus IFO, which took place from July 15 to 17, 1987. Values which were taken within an hour of local solar noon are presented and compared with the values computed for mu sub 0 = 1.0. The zenith angle for the measurements was between 11 and 18 deg. It is found that this method of inferring the optical depth indicates most clouds with optical depths within these limits. The measured curves have a slightly different shape than do the modeled ratios.

Hein, Paul F.↗
NASA NTRS2008

Atmospheric Correction at AERONET Locations: A New Science and Validation Data Set

This paper describes an AERONET-based Surface Reflectance Validation Network (ASRVN) and its dataset of spectral surface bidirectional reflectance and albedo based on MODIS TERRA and AQUA data. The ASRVN is an operational data collection and processing system. It receives 50x50 square kilometer subsets of MODIS L1B data from MODAPS and AERONET aerosol and water vapor information. Then it performs an accurate atmospheric correction for about 100 AERONET sites based on accurate radiative transfer theory with high quality control of the input data. The ASRVN processing software consists of L1B data gridding algorithm, a new cloud mask algorithm based on a time series analysis, and an atmospheric correction algorithm. The atmospheric correction is achieved by fitting the MODIS top of atmosphere measurements, accumulated for 16-day interval, with theoretical reflectance parameterized in terms of coefficients of the LSRT BRF model. The ASRVN takes several steps to ensure high quality of results: 1) cloud mask algorithm filters opaque clouds; 2) an aerosol filter has been developed to filter residual semi-transparent and sub-pixel clouds, as well as cases with high inhomogeneity of aerosols in the processing area; 3) imposing requirement of consistency of the new solution with previously retrieved BRF and albedo; 4) rapid adjustment of the 16-day retrieval to the surface changes using the last day of measurements; and 5) development of seasonal back-up spectral BRF database to increase data coverage. The ASRVN provides a gapless or near-gapless coverage for the processing area. The gaps, caused by clouds, are filled most naturally with the latest solution for a given pixels. The ASRVN products include three parameters of LSRT model (k(sup L), k(sup G), k(sup V)), surface albedo, NBRF (a normalized BRF computed for a standard viewing geometry, VZA=0 deg., SZA=45 deg.), and IBRF (instantaneous, or one angle, BRF value derived from the last day of MODIS measurement for specific viewing geometry) for MODIS 500m bands 1-7. The results are produced daily at resolution of 1 km in gridded format. We also provide cloud mask, quality flag and a browse bitmap image. The new dataset can be used for a wide range of applications including validation analysis and science research.

Wang, Yujie↗
DOE OSTI2022

Exploring Tradeoffs in Federated Learning on Serverless Computing Architectures

Federated learning is driving the development of new techniques to efficiently and securely use data across multiple sites while using diverse resources. One of these techniques is the use of the serverless computing paradigm to abstract away resource specific configurations, allowing federated learning across heterogeneous environments. However, deploying federated learning across edge resources, the cloud, and traditional HPC sites will require specialized approaches in order to best account for the weaknesses and strengths of each resource. In this work, we explore the new tradeoffs presented by managing a federated learning task across heterogeneous resources and demonstrate these tradeoffs with experiments using a serverless federated learning framework.

Baughman, Matt↗
DOE OSTI2026

Quantum Computing and Visualization Research Challenges and Opportunities

Here, quantum computing (QC) has experienced rapid growth in recent years with the advent of robust programming environments, readily accessible software simulators and cloud-based QC hardware platforms, and growing interest in learning how to design useful methods that leverage this emerging technology for practical applications. From the perspective of the field of visualization, this article examines research challenges and opportunities along the path from initial feasibility to practical use of QC platforms applied to meaningful problems.

Data visualization↗
DOE OSTI2022

A Vorticity Description of the Nuclear Cloud

We describe a model of the nuclear cloud in terms of the vorticity field associated with a buoyant vortex ring. A series of physical approximations are introduced that lower computational costs and render the model amenable for operational use. The determination of model parameters from the yield and emplacement of the weapon is also discussed.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2021

A Contrast Calibration Protocol for X-ray Speckle Visibility Spectroscopy

X-ray free electron lasers, with their ultrashort highly coherent pulses, opened up the opportunity of probing ultrafast nano- and atomic-scale dynamics in amorphous and disordered material systems via speckle visibility spectroscopy. However, the anticipated count rate in a typical experiment is usually low. Therefore, visibility needs to be extracted via photon statistics analysis, i.e., by estimating the probabilities of multiple photons per pixel events using pixelated detectors. Considering the realistic X-ray detector responses including charge cloud sharing between pixels, pixel readout noise, and gain non-uniformity, speckle visibility extraction relying on photon assignment algorithms are often computationally demanding and suffer from systematic errors. In this paper, we present a systematic study of the commonly-used algorithms by applying them to an experimental data set containing small-angle coherent scattering with visibility levels ranging from below 1% to ∼60%. We also propose a contrast calibration protocol and show that a computationally lightweight algorithm can be implemented for high-speed correlation evaluation.

47 OTHER INSTRUMENTATION↗
NASA NTRS1973

The inference of atmospheric ozone using satellite nadir measurements in the 1042/cm band

A description and detailed analysis of a technique for inferring atmospheric ozone information from satellite nadir measurements in the 1042 cm band are presented. A method is formulated for computing the emission from the lower boundary under the satellite which circumvents the difficult analytical problems caused by the presence of atmospheric clouds and the watervapor continuum absorption. The inversion equations are expanded in terms of the eigenvectors and eigenvalues of a least-squares-solution matrix, and an analysis is performed to determine the information content of the radiance measurements. Under favorable conditions there are only two pieces of independent information available from the measurements: (1) the total ozone and (2) the altitude of the primary maximum in the ozone profile.

Russell, J. M., III↗
NASA NTRS1977

The atmosphere of Saturn - An infrared perspective

A model of the radiative portion of the equatorial atmosphere of Saturn, constrained by the infrared data of various observers, has been constructed using a technique which includes the variation of thermal flux with depth. The model has a high-altitude temperature inversion due to the absorption of ultraviolet sunlight. The inversion causes the observed infrared emission peaks at 8 microns (methane) and 12 microns (ethane). Mixing ratios of these gases to hydrogen are computed from these emission features. The bottom of the modeled region occurs at the radiative convective boundary. At this level, an opaque cloud consisting of solid ammonia condensation particles is postulated. Above the cloud is a thin haze, also composed of ammonia particles. The haze is required to match infrared observations near 9.5 microns and hydrogen quadrupole equivalent widths near 0.64 micron. Predictions of the model are given for further observational tests.

Caldwell, J.↗
NASA NTRS1980

The thermal balance of Venus in light of the Pioneer Venus mission

Pioneer Venus orbiter and probes measured many of the properties of the Venus atmosphere which control its thermal balance and support its high surface temperature. Estimates based on orbiter data yield an effective radiating temperature of Venus of 228 + or - 5 K, corresponding to a solar emission of 153 + or - 13 W/sq cm. A mode of submicron particles is suggested as an important source of thermal opacity near the cloud tops to explain the orbiter and probe thermal flux measurements. A comparison of the measured solar flux profile with thermal fluxes computed from the measured temperature structure and composition shows that the greenhouse mechanism explains essentially all of the 500-K difference between the surface and radiating temperatures of Venus.

Tomasko, M. G.↗
NASA NTRS1984

Radiative heating rates near the stratospheric fountain

Radiative heating rates are computed for various sets of conditions thought to be appropriate to the stratospheric fountain region: with and without a layer of cirrus cloud between 100 and 150 mbar; with standard ozone and with decreased ozone in the lower stratosphere, again with and without the cirrus cloud; and with different temperatures in the tropopause region. The presence of the cloud decreases the radiative cooling below the cloud in the upper troposphere and increases the cooling above it in the lower stratosphere. The cloud is heated at the base and cooled at the top and thus radiatively destabilized; overall it gains energy by radiation. Decreasing ozone above the cloud also tends to cool the lower stratosphere. The net effect is a tendency for vertical convergence and horizontal divergence in the cloud region. High resolution profiles of temperature, ozone, and cloudiness within the fountain region are required in order to assess the final balance of the various processes.

Doherty, G. M.↗
NASA NTRS1987

Low cost, microcomputer-based interactive analysis system for direct-reception and archived remote sensing data

A hardware/software system has been developed for use in meteorological field experiments and by developing countries which need low-cost remote sensing data analysis capabilities. The system can directly receive satellite transmissions of the AVHRR, TOVS, Argos, GOES, GMS, and Meteosat systems. Also, the system can process computer tapes from Landsat. Received data are ingested directly into the computer's disk storage, eliminating the need for a wide-band analog tape drive. Data may be interpreted in terms of cloud imagery, cloudtop temperature, sea surface temperature, vegetation index, and temperature/humidity profiles with overlays of geographic boundaries and latitude/longitude grids. The image processing, enhancement functions, and modeling capabilities of the system are discussed.

Vermillion, Charles H.↗
NASA NTRS1989

Cirrus optical depth retrieval from satellite-measured bidirectional reflectance

In the framework of investigating the relationship between the visible optical depth and microphysics of cirrus clouds, the doubling scheme for radiative transfer in cirrus cloudy atmospheres, as developed by Takano and Liou (1988), has been used to compute the bidirectional reflectances at the top of the atmosphere. Reflectance data taken at about the same time from GOES and AVHRR over Waussau, as well as particle distributions observed during the FIRE IFO carried out in Wisconsin (1986) were the basis of the experiment. For the cirrus microphysical model, hexagonal ice crystals and area-equivalent ice spheres are considered. The single scattering phase functions for randomly oriented hexagonal columns and area-equivalent ice spheres are computed from geometric optics and Mie theory, respectively.

Takano, Y.↗
NASA NTRS1985

Cloud motion derived winds: Their accuracy, coverage, and suggestions for future improvement

Nature has provided us with a natural and easily visible method of tracing atmospheric motion through the measurement of cloud velocities. This source of wind information has been available from geosynchronous satellites since the launch of the ATS-1 Spin Scan camera. This sensor provided adequate spatial and temporal resolution views of individual cloud systems that could represent the wind with useful accuracy. During the last decade, cloud motion derived winds have become part of the operational system as they are routinely provided to the National Meteorological Center as input to the global numerical models. The principal limitations of cloud motion winds are that they (1) can be measured within the limits that cloud motions can represent the wind only where trackable clouds exist, (2) require knowledge of the cloud height, (3) require high spatial and temporal resolution geosynchronous satellite systems with high attitude determination accuracy, and (4) need sophisticated interactive computer systems for the calculation of high resolution fields. These limitations are examined and suggestions are made for how this product could be improved. Also, uses of the data for mesoscale purposes are discussed.

Shenk, William E.↗
NASA NTRS1994

Initial mass functions from ultraviolet stellar photometry: A comparison of Lucke and Hodge OB associations near 30 Doradus with the nearby field

UV stellar photometry is presented for 1563 stars within a 40 minutes circular field in the Large Magellanic Cloud (LMC), excluding the 10 min x 10 min field centered on R136 investigated earlier by Hill et al. (1993). Magnitudes are computed from images obtained by the Ultraviolet Imaging Telescope (UIT) in bands centered at 1615 A and 2558 A. Stellar masses and extinctions are estimated for the stars in associations using the evolutionary models of Schaerer et al. (1993), assuming the age is 4 Myr and that the local LMC extinction follows the Fitzpatrick (1985) 30 Dor extinction curve. The estimated slope of the initial mass function (IMF) for massive stars (greater than 15 solar mass) within the Lucke and Hodge (LH) associations is Gamma = -1.08 +/- 0.2. Initial masses and extinctions for stars not within LH associations are estimated assuming that the stellar age is either 4 Myr or half the stellar lifetime, whichever is larger. The estimated slope of the IMF for massive stars not within LH associations is Gamma = -1.74 +/- 0.3 (assuming continuous star formation), compared with Gamma = -1.35, and Gamma = -1.7 +/- 0.5, obtained for the Galaxy by Salpeter (1955) and Scalo (1986), respectively, and Gamma = -1.6 obtained for massive stars in the Galaxy by Garmany, Conti, & Chiosi (1982). The shallower slope of the association IMF suggests that not only is the star formation rate higher in associations, but that the local conditions favor the formation of higher mass stars there. We make no corrections for binaries or incompleteness.

Hill, Jesse K.↗
NASA NTRS2004

Simple Models of the Spatial Distribution of Cloud Radiative Properties for Remote Sensing Studies

This project aimed to assess the degree to which estimates of three-dimensional cloud structure can be inferred from a time series of profiles obtained at a point. The work was motivated by the desire to understand the extent to which high-frequency profiles of the atmosphere (e.g. ARM data streams) can be used to assess the magnitude of non-plane parallel transfer of radiation in thc atmosphere. We accomplished this by performing an observing system simulation using a large-eddy simulation and a Monte Carlo radiative transfer model. We define the 3D effect as the part of the radiative transfer that isn't captured by one-dimensional radiative transfer calculations. We assess the magnitude of the 3D effect in small cumulus clouds by using a fine-scale cloud model to simulate many hours of cloudiness over a continental site. We then use a Monte Carlo radiative transfer model to compute the broadband shortwave fluxes at the surface twice, once using the complete three-dimensional radiative transfer F(sup 3D), and once using the ICA F (sup ICA); the difference between them is the 3D effect given.

Source record↗