Decadal prediction of observed and simulated sea surface temperatures
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Timothy DelSole↗
SEARCH · Engineering Papers
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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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Comparing Observed Stellar Kinematics and Surface Densities in a Low-latitude Bulge Field to Galactic Population Synthesis Models
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Sean K. Terry↗
Synergy of Satellite Radiation, Precipitation, and Other Meteorological Variable Observations for Global Mean Sea Surface Turbulent Heat Flux Estimation
Sea surface turbulent heat flux is one of the key components in global freshwater and energy balances and plays an important role in atmospheric dynamics, thermodynamics and general circulation. This turbulent heat flux is dominantly decided by sea surface latent heat release with some contribution from sensible heat exchange. The flux and its anomaly could significantly affect ocean heat storage and ocean circulation. They are part of and have great impacts on climate variability. Though the turbulent heat flux is extremely important for the climate and weather systems, only very limited ship and buoy observations of the flux are available over open oceans. There are no global, operational, direct measurements of this crucial meteorological variable. Global estimates are, basically, indirectly calculated from bulk turbulent flux parameterization with a combination of satellite column water vapor, sea surface water temperature, and wind speed observations. Critical parameters such as sea surface air temperature and humidity are estimated from empirical relations of theses variables with the water vapor and sea surface water temperature, respectively. Lacking accurate knowledge on surface air temperature and humidity, uncertainties in the parameterization and potential changes in the non-linear turbulent processes with long-term climate variations could cause large errors in estimated long-term turbulent fluxes from the indirect method as shown in current global sea surface turbulent flux datasets. This study uses synergized data of satellite global radiation, precipitation, and other meteorological variable observations to estimate sea surface turbulent heat fluxes. The radiation observations are made by the satellite Clouds and the Earth’s Radiant Energy System (CERES) sensors, while the global precipitation data is from NASA’s satellite Global Precipitation Climatology Project (GPCP). Other data includes satellite sea surface water temperature and wind speed observations. These datasets are obtained from a wide range of space sensors from passive to active instruments and from visible and near infrared to thermal infrared and microwave spectral sounders. One significant feature of these datasets is that they have multi-decades long climate records. Top-of-atmosphere (TOA) radiation and its anomaly represents the net heat energy input to the climate system, and the oceanic precipitation and ocean-land moisture transport can be used to quantify sea surface latent heat release. Based on the synergized datasets and the principle of global water and energy balances, global mean turbulent heat fluxes are estimated. The turbulent heat anomalies for the first two decades of the 21st century are, then, obtained mainly from global CERES radiation and GPCP precipitation anomalies, along with CERES derived ocean-land heat transports. Analysis indicates that the uncertainties in the estimated turbulent flux anomalies may be reduced considerably. The results suggest a strong needs in synchronized and synergized observations of atmospheric radiation, precipitation, and oceanic meteorological variables for long-term climate studies.
Bing Lin↗
Evidence for the 3D Radiative Effects of Boundary-Layer Clouds From Observations of Direct and Diffuse Surface Solar Fluxes
Numerical experiments have revealed the importance of horizontal transport of light in the presence of clouds (“3D effects”), with consequences for climate, weather, and solar resource availability predictions. Yet, analysis of 3D effects from observations remain sparse because of the difficulty to isolate the effect of horizontal transport in radiation measurements. In this study, we provide observational evidence for 3D effects based on the direct-diffuse partition of surface solar fluxes. It is compared to outputs from the ecRad radiative transfer scheme run on retrieved cloud profiles. Furthermore, the direct-beam calculation takes careful account of the field-of-view of the pyrheliometer to ensure consistency between observed and modeled direct fluxes. Only the solver that accounts for 3D effects is able to reproduce the observed mean direct-diffuse partition as a function of solar zenith angle and cloud cover, in particular at large solar zenith angles where cloud sides intercept most of the direct beam.
54 ENVIRONMENTAL SCIENCES↗
Martian mesoscale circulations induced by variations in surface optical and thermal characteristics: A numerical study
According to Mariner 9 and Viking observations the surface albedo and the thermal inertia of Mars' surface vary substantially, and fairly large gradients also occur. The Syrtis Major region is bounded in the west by high-albedo cratered terrain and in the east by Isidis Planitia, a high-albedo plateau. Sinus Meridiani, centered at 0 degrees W 5 degrees S, is almost surrounded by higher albedo regions with sharp boundaries, and Acidalia Planitia, between 10 and 50 degrees W and north of 35 degrees N, has sharp albedo boundaries to the east and west. Observational and modeling studies, e.g., on Australian dry salt lake coasts, have shown that discontinuities and gradients in surface properties can induce mesoscale circulations. We have used a version of the DMUH mesoscale model to simulate atmospheric circulations induced by variations in the reflectivity and in the thermal inertia of the martian surface.
Siili, Tero↗
Venus - Global surface radio emissivity
Observations of thermal radio emission from the surface of Venus, made by the Pioneer Venus radar mapper at a wavelength of 17 cm, show variations that are dominated by changes in surface emissivity. The regions of lowest emissivity (0.54 + or - 0.05 for the highland areas of Aphrodite Terra and Theia Mons) correspond closely to regions of high radar reflectivity reported earlier. These results support the inference of inclusions of material with high electrical conductivity in the surface rock of these areas.
Ford, P. G.↗
Formation and Destruction of Ozone in Ices Relevant to Planetary and Satellite Surfaces
Ozone, O3, has been observed on the surfaces of Ganymede and the Saturnian satellites Dione and Rhea. It is generally accepted that in each case the O3 is formed by the magnetospheric irradiation of oxygen, O2, within water-rich icy surfaces. Carbon dioxide ice, which has been detected on a number of planetary-satellite surfaces, is another possible source of O3 after irradiation. Laboratory work to date has focused on O3 formation from irradiated O2 at 10 K using < 1O eV and 5 keV electrons and 100 keV protons. The temperature-dependent formation of O3 in solid O2 from 11 to 30 K using 5 keV electrons also has been examined. The objectives of the present laboratory study are (1) to compare O3 formation in O2 and CO2 ices using MeV proton and 10 keV electron bombardment at different temperatures, and (2) to examine ozone's thermal stability in different icy matrices (O2, CO2, H2O) during warming. Our results will aid in the understanding of these possible abiotic ozone sources, which is necessary when assessing O3 as a potential biomarker.
Moore, Marla H.↗
Ubiquitous strong electron–phonon coupling at the interface of FeSe/SrTiO 3
The observation of replica bands in single-unit-cell FeSe on SrTiO 3 (STO)(001) by angle-resolved photoemission spectroscopy (ARPES) has led to the conjecture that the coupling between FeSe electrons and the STO phonons are responsible for the enhancement of T c over other FeSe-based superconductors. However the recent observation of a similar superconducting gap in single-unit-cell FeSe/STO(110) raised the question of whether a similar mechanism applies. Here we report the ARPES study of the electronic structure of FeSe/STO(110). Similar to the results in FeSe/STO(001), clear replica bands are observed. We also present a comparative study of STO(001) and STO(110) bare surfaces, and observe similar replica bands separated by approximately the same energy, indicating this coupling is a generic feature of the STO surfaces and interfaces. Lastly, our findings suggest that the large superconducting gaps observed in FeSe films grown on different STO surface terminations are likely enhanced by a common mechanism.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports
The interfacial electronic structure of various size-selected metal oxide nanoclusters (M 3 O x ; M = Mo, Nb, Ti) on Cu(111) and a thin film of Cu 2 O supports were investigated in this paper by a combination of experimental methods and density functional theory (DFT). These systems explore electron transfer at the metal–metal oxide interface which can modify surface structure, metal oxidation states, and catalytic activity. Electron transfer was probed by measurements of surface dipoles derived from coverage dependent work function measurements using two-photon photoemission (2PPE) and metal core level binding energy spectra from X-ray photoelectron spectroscopy (XPS). The measured surface dipoles are negative for all clusters on Cu(111) and Cu 2 O/Cu(111), but those on the Cu 2 O surface are much larger in magnitude. In addition, sub-stoichiometric or “reduced” clusters exhibit smaller surface dipoles on both the Cu(111) and Cu 2 O surfaces. Negative surface dipoles for clusters on Cu(111) suggest Cu → cluster electron transfer, which is generally supported by DFT-calculated Bader charge distributions. For Cu 2 O/Cu(111), calculations of the surface electrostatic potentials show that the charge distributions associated with cluster adsorption structures or distortions at the cluster–Cu 2 O–Cu(111) interface are largely responsible for the observed negative surface dipoles. Changes observed in the XPS spectra for the Mo 3d, Nb 3d, and Ti 2p core levels of the clusters on Cu(111) and Cu 2 O/Cu(111) are interpreted with help from the calculated Bader charges and cluster adsorption structures, the latter providing information about the presence of inequivalent cation sites. Finally, the results presented in this work illustrate how the combined use of different experimental probes along with theoretical calculations can result in a more realistic picture of cluster–support interactions and bonding.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Cloud Properties Derived From GOES-7 for Spring 1994 ARM Intensive Observing Period Using Version 1.0.0 of ARM Satellite Data Analysis Program
This document describes the initial formulation (Version 1.0.0) of the Atmospheric Radiation Measurement (ARM) program satellite data analysis procedures. Techniques are presented for calibrating geostationary satellite data with Sun synchronous satellite radiances and for converting narrowband radiances to top-of-the-atmosphere fluxes and albedos. A methodology is documented for combining geostationary visible and infrared radiances with surface-based temperature observations to derive cloud amount, optical depth, height, thickness, temperature, and albedo. The analysis is limited to two grids centered over the ARM Southern Great Plains central facility in north-central Oklahoma. Daytime data taken during 5 Apr. - 1 May 1994, were analyzed on the 0.3 deg and 0.5 deg latitude-longitude grids that cover areas of 0.9 deg x 0.9 deg and 10 deg x 14 deg, respectively. Conditions ranging from scattered low cumulus to thin cirrus and thick cumulonimbus occurred during the study period. Detailed comparisons with hourly surface observations indicate that the mean cloudiness is within a few percent of the surface-derived sky cover. Formats of the results are also provided. The data can be accessed through the World Wide Web computer network.
Minnis, Patrick↗
Influence of Porosity and Pore Distributions on Strength Properties of Porous Alumina
In this work, strength properties of porous alumina with three different porosities as well as dense one were investigated to clarify porosity effects on strength properties. It was revealed that the strength had a general tendency to decrease drastically as increasing porosity. Spatial and size distributions of pores were characterized by observing specimen surfaces through a laser scanning microscope. Based on the observed pore characteristics, a procedure to estimate porosity effects on strength was newly developed in the framework of fracture mechanics, where a stress intensity factor-based criterion was applied for fracture of porous ceramics. In the procedure, it is assumed that porous ceramics have the same characteristics of crack distribution as those of pore distribution, and pores are presumed to be surrounded by virtual cracks. Monte Carlo simulations by using the procedure were carried out to estimate strength for four respective materials. Simulated strength coincided with experimentally observed one within a scatter band of factor of 2{sup 1/2}. Consequently, the developed procedure was confirmed to be efficient in evaluating effects of bulk porosity and pore distributions on strength of porous alumina.
36 MATERIALS SCIENCE↗
A self-consistent and spatially dependent model of the multiband emission of pulsar wind nebulae
A self-consistent and spatially dependent model is presented to investigate the multiband emission of pulsar wind nebulae (PWNe). In this model, a spherically symmetric system is assumed and the dynamical evolution of the PWN is included. The processes of convection, diffusion, adiabatic loss, radiative loss, and photon–photon pair production are taken into account in the electron’s evolution equation, and the processes of synchrotron radiation, inverse Compton scattering, synchrotron self-absorption, and pair production are included for the photon’s evolution equation. Both coupled equations are simultaneously solved. The model is applied to explain observed results of the PWN in MSH 15–52. Our results show that the spectral energy distributions (SEDs) of both electrons and photons are all a function of distance. The observed photon SED of MSH 15–52 can be well reproduced in this model. With the parameters obtained by fitting the observed SED, the spatial variations of photon index and surface brightness observed in the X-ray band can also be well reproduced. Moreover, it can be derived that the present-day diffusion coefficient of MSH 15–52 at the termination shock is κ{sub 0}=6.6×10{sup 24} cm{sup 2} s{sup −1}, the spatial average has a value of κ-bar =1.4×10{sup 25} cm{sup 2} s{sup −1}, and the present-day magnetic field at the termination shock has a value of B{sub 0}=26.6 μG and the spatial averaged magnetic field is B-bar =14.9 μG. The spatial changes of the spectral index and surface brightness at different bands are predicted.
79 ASTRONOMY AND ASTROPHYSICS↗
Evaluation of long-term Northern Hemisphere snow water equivalent products
Nine gridded Northern Hemisphere snow water equivalent (SWE) products were evaluated as part of the European Space Agency (ESA) Satellite Snow Product Intercomparison and Evaluation Exercise (SnowPEx). Three categories of datasets were assessed: (1) those utilizing some form of reanalysis (the NASA Global Land Data Assimilation System version 2 – GLDAS-2; the European Centre for Medium-Range Weather Forecasts (ECMWF) interim land surface reanalysis – ERA-Interim/Land and ERA5; the NASA Modern-Era Retrospective Analysis for Research and Applications version 1 (MERRA) and version 2 (MERRA-2); the Crocus snow model driven by ERA-Interim meteorology – Crocus); (2) passive microwave remote sensing combined with daily surface snow depth observations (ESA GlobSnow v2.0); and (3) stand-alone passive microwave retrievals (NASA AMSR-E SWE versions 1.0 and 2.0) which do not utilize surface snow observations. Evaluation included validation against independent snow course measurements from Russia, Finland, and Canada and product intercomparison through the calculation of spatial and temporal correlations in SWE anomalies. The stand-alone passive microwave SWE products (AMSR-E v1.0 and v2.0 SWE) exhibit low spatial and temporal correlations to other products and RMSE nearly double the best performing product. Constraining passive microwave retrievals with surface observations (GlobSnow) provides performance comparable to the reanalysis-based products; RMSE over Finland and Russia for all but the AMSR-E products is ∼50 mm or less, with the exception of ERA-Interim/Land over Russia. Using a seven-dataset ensemble that excluded the stand-alone passive microwave products reduced the RMSE by 10 mm (20 %) and increased the correlation from 0.67 to 0.78 compared to any individual product. The overall performance of the best multiproduct combinations is still at the margins of acceptable uncertainty for scientific and operational requirements; only through combined and integrated improvements in remote sensing, modeling, and observations will real progress in SWE product development be achieved.
Northern Hemisphere snow water equivalent (SWE) pr↗
Shapeshifting Nanocatalyst for CO2 Conversion
The conversion of CO2 into high-value chemicals through a photoreduction reaction in water is a promising route to reduce the dependence on fossil fuels. Enhancing selectivity toward hydrocarbons or alcohols can be achieved by Ag-Cu alloys. However, the stabilized surface state created by Ag-Cu interactions is still poorly understood. In this work, multi-modal in situ X-ray experiments reveals underlying mechanisms and the evolution of Ag-Cu nanoparticles under CO2 reduction reaction (CO2RR) conditions. Both morphological and chemical changes of Ag and Cu species induced by diffusion mechanics are tracked during nanocatalyst operation. The initial spheroid Ag-Cu nanoparticles are composed of a Cu-rich shell and Ag-rich core. The reduction treatment promotes Ag migration toward the surface. During photocatalytic CO2 reduction reaction, Cu atoms migrate back to the surface, forming Ag-Cu-O species. The study observes the surface oxidation of Cu(0) to Cu+ and the presence of Ag at the sub-surface region. Furthermore, nanoparticles change their shape, decreasing their specific surface area, driven by Cu diffusion during the CO2 photoreduction reaction. The results provide invaluable insights into the dynamic restructuring of the catalyst under reaction conditions and into the active species responsible for CO2 conversion.
CO2 reduction reaction↗
Very High-Cycle Fatigue Properties and Residual Stress Relaxation of Micro-shot-Peened EA4T Axle Steel
In this paper, EA4T alloy railway axle steel was shot peened with steel balls and ceramic balls with a diameter of 50 μm, and 10{sup 9}-cycle fatigue tests of unpeened and peened specimens were carried out. The fatigue properties and the surface compression residual stress relaxation processes were investigated. The results of surface fracture observation indicated that all the cracks initiated from the surface, and both peened and unpeened specimens have conventional fatigue limits in the very high-cycle fatigue regime. Moreover, compared with unpeened (UP) specimens, the fatigue limits were improved by 31 and 28% for ceramic shot-peened (CSP) and steel shot-peened (SSP) specimens, respectively. The improvement of fatigue limit is related to the surface compressive residual stresses (SCRS) and the surface-hardened layer. The SCRS and full-width half-maximum (FWHM) values during the relaxation processes have been analyzed. At stress amplitudes lower than the cyclic yield strength, the residual stress of SSP specimens relaxed quickly in the first loading cycle and then remained stable, while the residual stress of CSP specimens relaxed quickly in the first loading cycle and relaxed slowly afterward, then remained stable. For all SSP and CSP specimens with applied stress amplitudes larger than the cyclic yield strength, the residual stress relaxed quickly in the initial cycles, and then remained stable after the first loading cycle.
36 MATERIALS SCIENCE↗
Damage evolution and ductile fracture of commercially-pure titanium sheets subjected to simple tension and cyclic bending under tension
This paper describes a study into the evolution of damage in commercial-purity titanium (CP–Ti) sheets subjected to cyclic bending under tension (CBT) and uniaxial tension (simple tension, ST). Sections were taken from sheets that were strained to various levels under both methods and were imaged using X-ray computed tomography (XCT) to reveal insights into the size, density, and distribution of microvoids in the sheets. Digital image correlation (DIC) was also used to observe the surface strain of CBT and ST sheets during testing. These results showed that elongation to failure (ETF) for CBT deformation is about 2.5× higher than for ST, local longitudinal strains in the bulk of the CBT sample are around 1.3× higher than the peak strain in the ST necked region, and 1.7× higher in the localized region of CBT failure. It was found that the volume-density of voids in both sheets followed a similar exponential increase with strain, reaching nearly 45× higher in the CBT than the ST sheets before the onset of failure, mainly due to the higher strain levels achieved. A higher volume density of voids developed in the center of sheets at high levels of strain, for both processes, with the density in the sheet center becoming approximately double that found near the edges. Scanning electron microscopy (SEM) was used to examine the fracture surface of CBT and ST sheets after failure. The observations are presented and discussed highlighting the CBT process as effective to delay ductile fracture of the CP-Ti sheets.
Commercially pure titanium↗
Elucidating mechanisms of oxide growth and surface passivation on zinc thin film electrodes in alkaline solutions using the electrochemical quartz crystal microbalance
For this study, we utilized electrochemical quartz crystal microbalance to understand electrochemical passivation of the zinc electrode in alkaline media and subsequent oxide growth and stripping. The formation of native zinc oxide on a near pristine Zn surface upon contact with 1 M KOH electrolyte was observed. The surface was seen to roughen with time. During Zn dissolution, the measured mass-charge ratio corresponded to the removal of ZnO and not merely Zn. The mechanism of passivation was determined to be caused by electrochemical etching to form pores. The etching leads to a build-up of solid ZnO and Zn(OH) 2 due to electrochemical reactions on the surfaces of the pores. These reactions functionally close the pores off from the bulk. The cycle of Zn deposition and dissolution develops a porous network, which may be the origin of mossy Zn deposits that plague reversible Zn metal batteries.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
On the relative importance of the different initial conditions that seed the electrothermal instability
Electrothermal instability is responsible for degrading numerous applications of pulsed-power technology, yet the initial conditions from which it grows are not well understood. For the first time, metal surfaces have been tracked from characterization to self-emission. This reveals no clear correlation between non-uniform thermal emissions and surface metallurgical defects or crystallographic grains, while correlations are observed with surface topography for 5N metal but not 6061 metal. Finally, for 5N metal, surfaces with average roughness as small as 5nm still admit thermal perturbations with δT/T >0.1.
42 ENGINEERING↗