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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Diurnal variation of outgoing longwave radiation in the tropics

The diurnal harmonic in longwave emission in the tropical belt (30 deg N-30 deg S) is estimated from nine years of NOAA polar-orbiting satellite data. The results are compared successfully with Nimbus-7 ERB scanner data and with GOES-West geosynchronous satellite data. An interesting and consistent diurnal variation in longwave emission is found over the regions of intense oceanic convection, such as the ITCZ and SPCZ regions, with a peak-to-peak variation of 6-8 W/sq m and a maximum in the morning (0600-1200 LST). Histogram analysis indicates that this variation is associated with a diurnal variation in convective cloud (about 400 mb). Over regions of very intense convection, a diurnal variation of very high clouds (above 100 mb), which is out of phase with the variations at lower levels in the atmosphere, reduces the magnitude of the diurnal harmonic in longwave emission. It is interesting that histograms based on data averaged over 8-km and 250-km boxes give the same qualitative information about cloud and emission variability.

Hartmann, D. L.↗
NASA NTRS1988

Thematic mapper study of Alaskan ophiolites

The two principle objectives of the project Thematic Mapper Study of Alaskan Ophiolites were to further develop techniques for producing geologic maps, and to study the tectonics of the ophiolite terrains of the Brooks Range and Ruby Geanticline of northern Alaska. Ophiolites, sections of oceanic lithosphere emplaced along island arcs and continental margins, are important to the understanding of mountain belt evolution. Ophiolites also provide an opportunity to study the structural, lithologic, and geochemical characteristics of ocean lithosphere, yielding a better understanding of the processes forming lithosphere. The first part of the report is a description of the methods and results of the TM mapping and gravity modeling. The second part includes papers being prepared for publication. These papers are the following: (1) an analysis of basalt spectral variations; (2) a study of basalt geochemical variations; (3) an examination of the cooling history of the ophiolites using radiometric data; (4) an analysis of shortening produced by thrusting during the Brooks Range orogeny; and (5) a study of an ophiolite using digital aeromagnetic and topographic data. Additional papers are in preparation.

Bird, John M.↗
NASA NTRS1989

Global, seasonal cloud variations from satellite radiance measurements. I - Sensitivity of analysis

Global, daily, visible and IR radiance measurements from the NOAA-5 Scanning Radiometer (SR) are analyzed for the months of January, April, July and October, 1977 to infer cloud and surface radiative properties. In this paper, the data and analysis method are described. A unique feature of the method is that it utilizes radiative transfer models that simulate the SR measurements using explicit parameters representing the properties of the surface, atmosphere, and clouds. The accuracy of all the results depends primarily on the proper separation of the total radiance distribution into those parts representing clear and cloudy scenes.

Rossow, William B.↗
NASA NTRS2010

Variations on a Theme by Longhi: I, an Analysis of the Thermodynamic Underpinning of Fe, Mn, and Ni Partitioning into Olivine

Longhi et al. [1] have used the D(Ni) vs. D(Mg) parameterizations of Jones [2, 3] in attempting to explain the Ni systematics of lunar differentiation. A key element of the Jones parameterization and the Longhi et al. models is that, at very high temperatures, Ni may become incompatible in olivine. Unfortunately, there is no actual experimental evidence that this is ever the case [1]. To date, all experiments designed to demonstrate such incompatibility have failed. Here I will investigate the thermodynamic foundations of the D vs. D(Mg) trends for olivine/liquid discovered by [2].

Jones, John H.↗
DOE OSTI2020

Gradual polyploid genome evolution revealed by pan-genomic analysis of Brachypodium hybridum and its diploid progenitors

Abstract Our understanding of polyploid genome evolution is constrained because we cannot know the exact founders of a particular polyploid. To differentiate between founder effects and post polyploidization evolution, we use a pan-genomic approach to study the allotetraploid Brachypodium hybridum and its diploid progenitors. Comparative analysis suggests that most B. hybridum whole gene presence/absence variation is part of the standing variation in its diploid progenitors. Analysis of nuclear single nucleotide variants, plastomes and k-mers associated with retrotransposons reveals two independent origins for B. hybridum , ~1.4 and ~0.14 million years ago. Examination of gene expression in the younger B. hybridum lineage reveals no bias in overall subgenome expression. Our results are consistent with a gradual accumulation of genomic changes after polyploidization and a lack of subgenome expression dominance. Significantly, if we did not use a pan-genomic approach, we would grossly overestimate the number of genomic changes attributable to post polyploidization evolution.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1988

Minimal Joule dissipation models of magnetospheric convection

This paper gives a topical review of theoretical models of magnetospheric convection based on the concept of minimal Joule dissipation. A two-dimensional slab model of the ionosphere featuring an enhanced conductivity auroral oval is used to compute high-latitude electric fields and currents. Mathematical methods used in the modeling include Fourier analysis, fast Fourier transforms, and variational calculus. Also, conformal transformations are introduced in the analysis, which enable the auroral oval to be represented as a nonconcentric, crescent-shaped figure. Convection patterns appropriate to geomagnetic quiet and disturbed conditions are computed, the differentiating variable being the relative amount of power dissipated in the magnetospheric ring current. When ring current dissipation is small, the convection electric field is restricted to high latitudes (shielding regime), and when it is large, a significant penetration of the field to low latitudes occurs, accompanied by an increase in the ratio of the region I current to the region 2 current.

Barbosa, D. D.↗
NASA NTRS1994

Measurement of diurnal and semidiurnal rotational variations and tidal parameters of Earth

We discuss the determination of diurnal and semidiurnal variations in the rotation rate and the direction of rotation axis of Earth from the analysis of 8 years of very long baseline interferometry (VLBI) data. This analysis clearly show that these variations are largely periodic and tidally driven; that is, the periods of the variations correspond to the periods of the largest lunar and solar tides. For rotation rate variations, expressed in terms of changes in universal time (UT), the tidal lines with the largest observed signals are O1 (amplitude 23.5 microseconds in time (microseconds), period 25.82 solar hours); KL (18.9 microseconds, 23.93 hours); M2 (17.9 microseconds, 12.54 hours); and S2 (8.6 microseconds, 12.00 hours). For variations in the direction of the rotation axis (polar motion), significant signals exist in the retrograde semidiurnal band at the M2 and S2 tides (amplitudes 265 and 119 microarc seconds (microarc seconds, respectively); the prograde diurnal band at the O1, K1, and P1 tides (amplitudes 199, 152, and 60 microarc seconds, respectively); and the prograde semidiurnal band at the M2 and K2 tides (amplitudes 58 and 39 microarc seconds, respectively). Variations in the retrograde diurnal band are represented by corrections with previous estimates except that a previously noted discrepancy in the 13.66-day nutation (corresponding to the O1 tide) is largely removed in this new analysis. We estimate that the standard deviations of these estimates are 1.0 microseconds for the UT1 variations and 14-16 microarc seconds for the polar motion terms. These uncertainties correspond to surface displacements of approximately 0.5 mm. From the analysis of atmospheric angular momentum data we conclude that variations in UT1 excited by the atmosphere with subdaily periods are small (approximately 1 microsecond). We find that the average radial tidal displacements of the VLBI sites in the diurnal band are largely consistent with known deficiencies in current tidal models, i.e., deficiencies of up to 0.9 mm in the treatment of the free core nutation resonance. In the semidiurnal band, our analysis yields estimates of the second-degree harmonic radial Love number h(sub 2) at the M2 tide of 0.604 + i0.005 +/- 0.002. The most likely explanation for the rotational variations are the effects of ocean tides, but there may also be some contributions from atmospheric tides, the effects of triaxiality of Earth, and the equatorial second-degree-harmonic components of the core- mantle boundary.

Herring, Thomas A.↗
DOE OSTI2020

Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution

3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique – global Very Long Baseline Interferometry (VLBI) at 1.3 mm (230 GHz) – to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable γ-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array (ALMA), at an angular resolution of ∼20 μas (at a redshift of z = 0.536 this corresponds to ∼0.13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation. We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across different imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI “core”. This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet. We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1.3 and ∼1.7 μas day−1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3 mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≲1010 K, a magnitude or more lower than typical values seen at ≥7 mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.Key words: galaxies: active / galaxies: jets / galaxies: individual: 3C 279 / techniques: interferometric⋆ The data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A69 and at https://eventhorizontelescope.org/for-astronomers/data⋆⋆ Deceased.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1974

Variability of the observed temperature, 20-60 km at 80 deg N to 40 deg S

Results are presented for a periodic analysis of atmospheric temperature variations at heights of from 20 to 60 km between 80 deg N and 40 deg S. The analysis is based on Meteorological Rocket Network temperatures not corrected for solar radiation or aliasing by the diurnal tide, and the frequencies examined include the long-term mean, the quasi-biennial oscillation (QBO), and the first six harmonics of the annual wave. Amplitudes are plotted for the long-term mean and QBO as well as for the annual, semiannual, and terannual components. The results show two distinct annual oscillations (the high-latitude one and another above the tropical stratopause) and a polar semiannual wave with two centers of large amplitude that are 90 deg out of phase and separated by a zone of minimum amplitude near 45 km.

Nastrom, G. D.↗
NASA NTRS2000

Improving Global Reanalyses and Short Range Forecast Using TRMM and SSM/I-Derived Precipitation and Moisture Observations

Global reanalyses currently contain significant errors in the primary fields of the hydrological cycle such as precipitation, evaporation, moisture, and the related cloud fields, especially in the tropics. The Data Assimilation Office (DAO) at the NASA Goddard Space Flight Center has been exploring the use of tropical rainfall and total precipitable water (TPW) observations from the TRMM Microwave Imager (TMI) and the Special Sensor Microwave/ Imager (SSM/I) instruments to improve short-range forecast and reanalyses. We describe a "1+1"D procedure for assimilating 6-hr averaged rainfall and TPW in the Goddard Earth Observing System (GEOS) Data Assimilation System (DAS). The algorithm is based on a 6-hr time integration of a column version of the GEOS DAS, hence the "1+1"D designation. The scheme minimizes the least-square differences between the observed TPW and rain rates and those produced by the column model over the 6-hr analysis window. This 1+lD scheme, in its generalization to four dimensions, is related to the standard 4D variational assimilation but uses analysis increments instead of the initial condition as the control variable. Results show that assimilating the TMI and SSM/I rainfall and TPW observations improves not only the precipitation and moisture fields but also key climate parameters such as clouds, the radiation, the upper-tropospheric moisture, and the large-scale circulation in the tropics. In particular, assimilating these data reduce the state-dependent systematic errors in the assimilated products. The improved analysis also provides better initial conditions for short-range forecasts, but the improvements in forecast are less than improvements in the time-averaged assimilation fields, indicating that using these data types is effective in correcting biases and other errors of the forecast model in data assimilation.

Hou, Arthur Y.↗
NASA NTRS1993

Temporal variations in the termination shock distance

A kinematic analysis is made of solar wind driven temporal variations in the heliospheric termination shock distance. This has become possible because the large-scale dynamics of, and temporal variations in the distant solar wind are now well enough known from a combination of in situ and remote measurements. Conversely, nothing is known of the corresponding properties in the local interstellar medium, and hence these will be ignored. Given specific assumptions for how the termination shock responds to solar wind fluctuations, it is shown that the termination shock is very agile, moving in and out by up to a few AU in a month. This conclusion holds for a broad range of shock response assumptions. Because a spacecraft moves slowly in comparison to the termination shock, the shock will sweep back and forth over the spacecraft once the shock is first encountered.

Suess, S. T.↗
DOE OSTI2024

Effects of Nonequilibrium Atomic Structure on Ionic Diffusivity in LLZO: A Classical and Machine Learning Molecular Dynamics Study

To improve the performance of electrochemical devices, it is essential to understand the effects of nonequilibrium motifs in solids, such as grain boundaries, amorphous phases, and highly strained regions, on atomic-scale transport and stability. Molecular dynamics simulations are used to explore the combined effect of far-from-equilibrium atomic structures and the choice of interatomic potential on ionic diffusivity predictions for Li 7 La 3 Zr 2 O 12 (LLZO), a promising solid electrolyte for all-solid-state batteries. Amorphization and high strain are considered using both classical Buckingham interatomic potentials and machine learning force fields. Here we find that both crystalline expansion and amorphization tend to slow diffusion, although the different physical encodings in the two potentials impact the properties in different ways. We trace these variations to a combination of structural and transport factors, the contributions of which are deconvoluted computationally. Graph-based analysis reveals that the variations for amorphous LLZO arise from the connectivity of diffusion pathways within the predicted structures, which generally correlates with diffusivity and is notably higher for structures generated by the machine learning force fields. Our study provides additional insight into the relationship between atomic structure and diffusivity in LLZO, while also highlighting the need for care in choosing and validating potentials to simulate far from equilibrium structures.

25 ENERGY STORAGE↗
NASA NTRS1999

Improving Global Reanalyses and Short-Range Forecast Using TRMM and SSM/I-Derived Precipitation and Moisture Observations

Global reanalyses currently contain significant errors in the primary fields of the hydrological cycle such as precipitation, evaporation, moisture, and the related cloud fields, especially in the tropics. The Data Assimilation Office (DAO) at the NASA Goddard Space Flight Center has been exploring the use of tropical rainfall and total precipitable water (TPW) observations from the TRMM Microwave Imager (TMI) and the Special Sensor Microwave/ Imager (SSM/I) instruments to improve short-range forecast and reanalyses. We describe a 1+1D procedure for assimilating 6-hr averaged rainfall and TPW in the Goddard Earth Observing System (GEOS) Data Assimilation System (DAS). The algorithm is based on a 6-hr time integration of a column version of the GEOS DAS, hence the 1+1D designation. The scheme minimizes the least-square differences between the observed TPW and rain rates and those produced by the column model over the 6-hr analysis window. This 1+1D scheme, in its generalization to four dimensions, is related to the standard 4D variational assimilation but uses analysis increments instead of the initial condition as the control variable. Results show that assimilating the TMI and SSW rainfall and TPW observations improves not only the precipitation and moisture fields but also key climate parameters such as clouds, the radiation, the upper-tropospheric moisture, and the large-scale circulation in the tropics. In particular, assimilating these data reduce the state-dependent systematic errors in the assimilated products. The improved analysis also provides better initial conditions for short-range forecasts, but the improvements in forecast are less than improvements in the time-averaged assimilation fields, indicating that using these data types is effective in correcting biases and other errors of the forecast model in data assimilation.

Hou, Arthur Y.↗
NASA NTRS2006

Solar Electric Propulsion for Primitive Body Science Missions

This paper describes work that assesses the performance of solar electric propulsion (SEP) for three different primitive body science missions: 1) Comet Rendezvous 2) Comet Surface Sample Return (CSSR), and 3) a Trojan asteroid/Centaur object Reconnaissance Flyby. Each of these missions launches from Earth between 2010 and 2016. Beginning-of-life (BOL) solar array power (referenced at 1 A.U.) varies from 10 to 18 kW. Launch vehicle selections range from a Delta II to a Delta IV medium-class. The primary figure of merit (FOM) is net delivered mass (NDM). This analysis considers the effects of imposing various mission constraints on the Comet Rendezvous and CSSR missions. Specifically, the Comet Rendezvous mission analysis examines an arrival date constraint with a launch year variation, whereas the CSSR mission analysis investigates an Earth entry velocity constraint commensurate with past and current missions. Additionally, the CSSR mission analysis establishes NASA's New Frontiers (NF) Design Reference Mission (DRM) in order to evaluate current and future SEP technologies. The results show that transfer times range from 5 to 9 years (depending on the mission). More importantly, the spacecraft's primary propulsion system performs an average 5-degree plane change on the return leg of the CSSR mission to meet the previously mentioned Earth entry velocity constraint. Consequently, these analyses show that SEP technologies that have higher thrust-to-power ratios can: 1) reduce flight time, and 2) change planes more efficiently.

Witzberger, Kevin E.↗
NASA NTRS2006

SABER (TIMED) and MLS (UARS) Temperature Observations of Mesospheric and Stratospheric QBO and Related Tidal Variations

More than three years of temperature observations from the SABER (TIMED) and MLS WARS) instruments are analyzed to study the annual and inter-annual variations extending from the stratosphere into the upper mesosphere. The SABER measurements provide data from a wide altitude range (15 to 95 km) for the years 2002 to 2004, while the MLS data were taken in the 16 to 55 km altitude range a decade earlier. Because of the sampling properties of SABER and MLS, the variations with local solar time must be accounted for when estimating the zonal mean variations. An algorithm is thus applied that delineates with Fourier analysis the year-long variations of the migrating tides and zonal mean component. The amplitude of the diurnal tide near the equator shows a strong semiannual periodicity with maxima near equinox, which vary from year to year to indicate the influence from the Quasi-biennial Oscillation (QBO) in the zonal circulation. The zonal mean QBO temperature variations are analyzed over a range of latitudes and altitudes, and the results are presented for latitudes from 48"s to 48"N. New results are obtained for the QBO, especially in the upper stratosphere and mesosphere, and at mid-latitudes. At Equatorial latitudes, the QBO amplitudes show local peaks, albeit small, that occur at different altitudes. From about 20 to 40 km, and within about 15" of the Equator, the amplitudes can approach 3S K for the stratospheric QBO or SQBO. For the mesospheric QBO or MQBO, we find peaks near 70 km, with temperature amplitudes reaching 3.5"K, and near 85 km, the amplitudes approach 2.5OK. Morphologically, the amplitude and phase variations derived from the SABER and MLS measurements are in qualitative agreement. The QBO amplitudes tend to peak at the Equator but then increase again pole-ward of about 15" to 20'. The phase progression with altitude varies more gradually at the Equator than at mid-latitudes. A comparison of the observations with results from the Numerical Spectral Model (NSM) reveals that there is qualitative agreement. The NSM generates the QBO extending from the stratosphere into the upper mesosphere, with temperature variations extending to mid latitudes, but the predicted amplitudes are smaller than those observed.

Huang, Frank T.↗
DOE OSTI2020

Enriched East Asian oxygen isotope of precipitation indicates reduced summer seasonality in regional climate and westerlies

Speleothem oxygen isotope records over East Asia reveal apparently large and rapid paleoclimate changes over the last several hundred thousand years. However, what the isotopic variation actually represent in terms of the regional climate and circulation is debated. We present an answer that emerges from an analysis of the interannual variation in amount-weighted annual δ 18 O of precipitation over East Asia as simulated by an isotope-enabled model constrained by large-scale atmospheric reanalysis fields. 18 O-enriched years have reduced summer seasonality both in terms of precipitation isotopes and in the large-scale circulation. Changes occur between June and October, where the δ 18 O of precipitation (δ 18 O p ) transitions from the isotopically heavier winter to the lighter summer regime. For 18 O-enriched years, this transition is less pronounced. Variations in precipitation amount alone are insufficient to explain the amount-weighted annual δ 18 O p between 18 O-enriched and 18 O-depleted years. Reduced summer seasonality is also expressed in the low-level monsoonal southerlies and upper-level westerlies; for the latter, the northward migration across the Tibetan Plateau in the summer is less pronounced. Our result thus implicates the westerlies across the plateau as the proximate cause of East Asian paleomonsoon changes, manifested as a modulation of its summer peak.

54 ENVIRONMENTAL SCIENCES↗