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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Performance Evaluation of Weather@home2 Simulations over West African Region

Weather and climate forecasting, using climate models, have become essential tools and life-savers in the West African region; in spite of the fact that climate models do not fully comply with attributes of forecast qualities—RASAP: reliability, association, skill, accuracy, and precision. The objective of this paper is to quantitatively evaluate, in comparison to CRU and ERA5 datasets, the RASAP compliance-level of the weather@home2 modeling system (w@h2). Findings from some statistical evaluations show that, to a moderately significant extent, w@h2 model provides useful information during the monsoon seasons; skills to capture the Little Dry Season over the Guinea zone; predictive skills for the onset season; ability to reproduce all the annual characteristics of the surface maximum air temperature over the region; as well as skill to detect heat waves that usually ravage West Africa during the boreal spring. The model displays traces of attributes that are needed for seasonal climate predictions and applications. Deficiencies in the quantitative reproducibility point to the facts that the model does provide a reliability akin to that of regional climate models. This paper further furnishes a prospective user with information on whether the model might be “useful or not” for a particular application.

West Africa↗
DOE OSTI2023

Carbon cycle extremes accelerate weakening of the land carbon sink in the late 21st century

Increasing surface temperature could lead to enhanced evaporation, reduced soil moisture availability, and more frequent droughts and heat waves. The spatiotemporal co-occurrence of such effects further drives extreme anomalies in vegetation productivity and net land carbon storage. However, the impacts of climate change on extremes in net biospheric production (NBP) over longer time periods are unknown. Using the percentile threshold on the probability distribution curve of NBP anomalies, we computed negative and positive extremes in NBP. Here we show that due to climate warming, about 88% of global regions will experience a larger magnitude of negative NBP extremes than positive NBP extremes toward the end of 2100, which accelerate the weakening of the land carbon sink. Our analysis indicates the frequency of negative extremes associated with declines in biospheric productivity was larger than positive extremes, especially in the tropics. While the overall impact of warming at high latitudes is expected to increase plant productivity and carbon uptake, high-temperature anomalies increasingly induce negative NBP extremes toward the end of the 21st century. Using regression analysis, we found soil moisture anomalies to be the most dominant individual driver of NBP extremes. The compound effect of hotness, dryness, and fire caused extremes at more than 50% of the total grid cells. The larger proportion of negative NBP extremes raises a concern about whether the Earth is capable of increasing vegetation production with a growing human population and rising demand for plant material for food, fiber, fuel, and building materials. The increasing proportion of negative NBP extremes highlights the consequences not only of reduction in total carbon uptake capacity but also of conversion of land to a carbon source.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Systematically tracking the hourly progression of large wildfires using GOES satellite observations

Abstract. In the western United States, prolonged drought, a warming climate, and historical fuel buildup have contributed to larger and more intense wildfires as well as to longer fire seasons. As these costly wildfires become more common, new tools and methods are essential for improving our understanding of the evolution of fires and how extreme weather conditions, including heat waves, windstorms, droughts, and varying levels of active-fire suppression, influence fire spread. Here, we develop the Geostationary Operational Environmental Satellites (GOES)-Observed Fire Event Representation (GOFER) algorithm to derive the hourly fire progression of large wildfires and create a product of hourly fire perimeters, active-fire lines, and fire spread rates. Using GOES-East and GOES-West geostationary satellite detections of active fires, we test the GOFER algorithm on 28 large wildfires in California from 2019 to 2021. The GOFER algorithm includes parameter optimizations for defining the burned-to-unburned boundary and correcting for the parallax effect from elevated terrain. We evaluate GOFER perimeters using 12 h data from the Visible Infrared Imaging Radiometer Suite (VIIRS)-derived Fire Event Data Suite (FEDS) and final fire perimeters from the California's Fire and Resource Assessment Program (FRAP). Although the GOES imagery used to derive GOFER has a coarser resolution (2 km at the Equator), the final fire perimeters from GOFER correspond reasonably well to those obtained from FRAP, with a mean Intersection-over-Union (IoU) of 0.77, in comparison to 0.83 between FEDS and FRAP; the IoU indicates the area of overlap over the area of the union relative to the reference perimeters, in which 0 is no agreement and 1 is perfect agreement. GOFER fills a key temporal gap present in other fire tracking products that rely on low-Earth-orbit imagery, where perimeters are available at intervals of 12 h or longer or at ad hoc intervals from aircraft overflights. This is particularly relevant when a fire spreads rapidly, such as at maximum hourly spread rates of over 5 km h−1. Our GOFER algorithm for deriving the hourly fire progression using GOES can be applied to large wildfires across North and South America and reveals considerable variability in the rates of fire spread on diurnal timescales. The resulting GOFER product has a broad set of potential applications, including the development of predictive models for fire spread and the improvement of atmospheric transport models for surface smoke estimates. The resulting GOFER product has a broad set of potential applications, including the development of predictive models for fire spread and the improvement of atmospheric transport models for surface smoke estimates (https://doi.org/10.5281/zenodo.8327264, Liu et al., 2023).

Geology↗
DOE OSTI2021

TempestExtremes v2.1: a community framework for feature detection, tracking, and analysis in large datasets

TempestExtremes (TE) is a multifaceted framework for feature detection, tracking, and scientific analysis of regional or global Earth system datasets on either rectilinear or unstructured/native grids. Version 2.1 of the TE framework now provides extensive support for examining both nodal (i.e., pointwise) and areal features, including tropical and extratropical cyclones, monsoonal lows and depressions, atmospheric rivers, atmospheric blocking, precipitation clusters, and heat waves. Available operations include nodal and areal thresholding, calculations of quantities related to nodal features such as accumulated cyclone energy and azimuthal wind profiles, filtering data based on the characteristics of nodal features, and stereographic compositing. This paper describes the core algorithms (kernels) that have been added to the TE framework since version 1.0, including algorithms for editing pointwise trajectory files, composition of fields around nodal features, generation of areal masks via thresholding and nodal features, and tracking of areal features in time. Several examples are provided of how these kernels can be combined to produce composite algorithms for evaluating and understanding common atmospheric features and their underlying processes. These examples include analyzing the fraction of precipitation from tropical cyclones, compositing meteorological fields around extratropical cyclones, calculating fractional contribution to poleward vapor transport from atmospheric rivers, and building a climatology of atmospheric blocks.

58 GEOSCIENCES↗
DOE OSTI2023

Warming of the Willamette River, 1850–present: the effects of climate change and river system alterations

Abstract. Using archival research methods, we recovered and combined data from multiple sources to produce a unique, 140-year record of daily water temperature (Tw) in the lower Willamette River, Oregon (1881–1890, 1941–present). Additional daily weather and river flow records from the 1850s onwards are used to develop and validate a statistical regression model of Tw for 1850–2020. The model simulates the time-lagged response of Tw to air temperature and river flow and is calibrated for three distinct time periods: the late 19th, mid-20th, and early 21st centuries. Results show that Tw has trended upwards at 1.1 ∘C per century since the mid-19th century, with the largest shift in January and February (1.3 ∘C per century) and the smallest in May and June (∼ 0.8 ∘C per century). The duration that the river exceeds the ecologically important threshold of 20 ∘C has increased by about 20 d since the 1800s, to about 60 d yr−1. Moreover, cold-water days below 2 ∘C have virtually disappeared, and the river no longer freezes. Since 1900, changes are primarily correlated with increases in air temperature (Tw increase of 0.81 ± 0.25 ∘C) but also occur due to alterations in the river system such as depth increases from reservoirs (0.34 ± 0.12 ∘C). Managed release of water affects Tw seasonally, with an average reduction of up to 0.56 ∘C estimated for September. River system changes have decreased variability (σ) in daily minimum Tw by 0.44 ∘C, increased thermal memory, reduced interannual variability, and reduced the response to short-term meteorological forcing (e.g., heat waves). These changes fundamentally alter the response of Tw to climate change, posing additional stressors on fauna.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

CLMU Interactions between UHIs and HWs Experiments

User namelist settings, code changes, and driving scripts to set to CLM5 on NERSC for investigating the interactions between urban heat islands (UHI) and heat waves (HWs) at the continental and daily mean scales over the Contiguous United States (CONUS). More details are available in README.md.

Climate Change↗
DOE OSTI2023

Modeling the U.S. Western Electric Interconnection to Understand the Consequences of Hydrometeorological Extremes and Options for Risk Mitigation

Electricity grid operators around the world face a dual challenge; withstanding increasingly severe weather and the longer term impacts of climate change, while simultaneously decarbonizing. Extreme weather events such as heat waves and droughts are rising in both severity and frequency, which is threatening the reliability of electricity grids through increased demand, generation capacity losses, and equipment failures. Consequently, incorporating hydrometeorological stressors into computational power systems analysis is becoming an even more critical tool in long term planning and short term operations. However, there is a general lack of open-source customizable grid simulation software capable of exhaustively stress testing the grid under hydrometeorological uncertainty, and/or examining potential risk mitigation pathways. A related, persistent challenge for power system modelers is striking an appropriate balance between model fidelity (e.g. spatial scale and time resolution) and computational tractability (wall clock run-time). In this study, we are proposing a solution to this problem with open-source software that allows users to seamlessly customize the scale and track the accuracy of grid operations models. Our approach allows users to search over numerous model parameters (network topology, mathematical formulation, economic hurdle rates, and transmission line scaling) to identify model instantiations that accommodate experimental design. Further, we use this approach to demonstrate the importance of including extreme weather events in model validation and model selection. Focusing on the occurrence of heatwaves and droughts in the U.S. Western Interconnection, we examine role of extreme events in balancing tradeoffs between model fidelity and run-time at the model design stage.

Economics↗
NASA NTRS1973

Theoretical understanding of chromospheric inhomogeneities

Detailed theoretical studies of chromospheric inhomogeneities consider dynamics as well as radiative transfer of mass flow as a consequence of energy deposition. It is shown that pressure is exerted by the heating waves, especially in inhomogeneous structures, where they can be defracted. A dynamical model is formulated that depicts the inhomogeneous structure of the chromosphere-corona transition region through mass flow regimes.

Delache, P.↗
NASA NTRS1978

A solar wind experiment for the solar probe mission

Electron and ion plasma measurements on Solar Probe are important, especially to elucidate the role of coronal holes as sources of the solar wind and to resolve the long debated question of the importance of wave heating within 20 solar radii to the acceleration of the solar wind. Adaptable instruments are required to cover the large dynamic range of parameters between 1 AU and 4 solar radii. The baseline mission would be improved, in some respects, by the addition of a second spacecraft, following the first by a distance of several solar radii. A spinning spacecraft would be satisfactory, but not essential, for the present objectives. Attention should be paid to having the heat shield electrically conducting. An instrument for ion and electron (but no composition) measurements would have a mass of approximately 10 kg, require 8 w of power, and generate data at a maximum rate of approximately 2 kbits/sec.

Ogilvie, K. W.↗
NASA NTRS1977

Mass and energy flow in the solar chromosphere and corona

The work reviews some investigations into the mass and energy flow in the solar chromosphere and corona; the objective of these investigations is the development of a physical model that will not only account for the physical conditions in the outer atmosphere of the sun, but can also be applied to the study of the outer atmospheres of other stars. Particular attention is given to mass and energy flow in regions with weak and strong magnetic fields, to observational evidence for wave heating and systematic mass flows, and to heating mechanisms. Consideration is given throughout to mechanisms of energy input and energy loss.

Withbroe, G. L.↗
NASA NTRS1977

Spontaneous emission from ScF in a supersonic mixing flame

An investigation was conducted of the two reactions: Sc + F2 yields ScF(asterisk) + F and Y + Cl2 yields YCl(asterisk) + Cl. Experiments were designed for studying the reactions under the relatively high pressure conditions (5-20 torr) appropriate for chemical laser operation. A shock tube was used to provide a short duration flow through a supersonic nozzle array. Shock wave heating is used to dissociate the ScCl3 or YCl3 at temperatures of about 6000 K, before the gases are accelerated and expanded through the supersonic nozzle array. The expanded primary flow is then mixed with a secondary flow of F2 introduced through slots at the trailing edge of each nozzle blade. Graphs show the temporal behavior of the visible spontaneous emission over the range from 3000 to 9000 A for a typical test condition, a microdensitometer tracing of the visible emission over the range from 4000 to 7000 A, and the spontaneous emission from ScF(asterisk) obtained by computer image processing of intensity data.

Fischell, D. R.↗
NASA NTRS1981

X-ray emission from supernova remnants near gamma-ray sources

It is noted that the imaging proportional of the Einstein Observatory has been used to search for X-ray emission from eight radio supernova remnants which are near three of the Cos-B unidentified gamma-ray sources: 2CG 311-01, CG 327-0, and CG 333+0. Emissions are observed from three of the remnants and upper limits on the remainder which are consistent with the luminosity expected from a simple blast-wave heated plasma model of the process. Thus none of the remnants are superluminous as might be expected if the pattern of the Crab Nebula were followed. It is thought that the remnant RCW 103 may be Vela-like. It is noted that another of the remnants, Kes 27, has centrally peaked X-ray emission which is unlike the shell-like emission seen for many remnants and which does not correlate well with its asymmetric radio emission.

Lamb, R. C.↗
NASA NTRS1982

Mass loss from cool stars, facts, fads, and fallacies

The accumulation of observational material (ultraviolet spectroscopic measures, quantitative optical spectroscopy, and X-ray photometry) and its use in discerning the presence and character of mass loss across the cool half of the H-R diagram and establishing constraints on theoretical models are discussed. Analogies with closed and open solar magnetic structures are found. Two determinants of atmospheric wind structure, temperature and gravity, may suffice in a most superficial way to define the wind and atmospheric structure in a star, however it is apparent that there is still a missing parameter which may stem from magnetic activity and its particular configuration. Theories that appear successful in reproducing observed line profiles, wind temperatures, and terminal velocities incorporate Alfven wave heating and momentum deposition. Successive observations of an active binary (lambda and G8III-IV) and a supergiant star, alpha Aqr (G2 Ib) revealed that magnetic activity and perhaps mass loss occur on restricted regions of a stellar surface and that long-term structures are present in the wind. These phenomena are present in the solar atmosphere and wind and may be considered a general characteristic of stellar winds.

Dupree, A. K.↗
NASA NTRS1981

Theory of stellar coronae - An interpretation of X-ray emission from non-degenerate stellar sources

It is shown that the acoustic wave heating theory of stellar coronae explains neither Einstein Observatory coronae data nor previous UV and X-ray observations of the sun and other stars, on the evidence of data implying that magnetic fields, stellar rotation rates and convection zone parameters figure in the determination of coronal heating. Einstein Observatory results suggest that O-type star coronae are heated by the interaction of turbulent stellar winds with slowly-decaying primordial magnetic fields or by radiative instabilities in the flow. The apparent absence of coronae in Ap stars is due to the stability of atmospheres in which even weak convection is suppressed by the strong field. Dynamo action is implicated in some normal A-type stars and in F- and later-type dwarfs. Coronal characteristics of dMe and dM stars, close binaries, and K- and M-type giants are also considered.

Linsky, J. L.↗
NASA NTRS1982

Parameterization of IR cooling in a middle atmosphere dynamics model. I - Effects on the zonally averaged circulation

A computationally efficient two-stream parameterization of IR cooling is developed for a middle atmosphere dynamics model. The parameterization combines the monochromatic feature of an emissivity formulation with the computational simplicity of a single spatial integral to evaluate the monochromatic transfer equation. Calculations show strong radiative control of the mesopause region and the need for substantial deceleration of the mean zonal winds. Calculated temperatures show good agreement in the summer hemisphere where planetary wave activity is negligible, but in the polar night of the winter hemisphere they are about 30 K too cold, which suggests planetary wave heating must make up the deficit. With observed ozone densities, globally averaged radiative equilibrium temperatures in the 65-75 km region are too cold and an additional heat source about 1 K/day is required.

Apruzese, J. P.↗
NASA NTRS1983

Theoretical studies of chromospheres and winds in cool stars

The formation of spectral lines in expanding spherical atmospheres was determined in a physically realistic way, taking into account multilevel atomic processes, partial frequency redistribution, and other non-LTE transfer effects that affect the formation of optically thick lines. The formation of MgII and Ca II circumstellar absorption lines in late type giants and supergiants is investigated. The radiative cooling rate as a function of density and temperature was calculated from the results of plane parallel chromospheric models and these results were used to approximate the radiative cooling in an extended wind. The run of temperature was calculated along with the density and velocity profiles. The most important prediction of these models is that a warm zone in the wind must exist as a result of the wave heating. Within this zone, the Ca II and Mg II atoms can be ionized to Ca III and Mg III, so that the gas is transparent in the resonance transitions.

Dupree, A.↗
NASA NTRS1984

Measurement of vacuum space potential by an emissive probe

The use of an electron-emitting probe (Langmuir and Compton, 1931) to measure the space potential in the vacuum between parallel metal plates is demonstrated, extending the inflection-point interpretation technique of Smith et al. (1979) to the vacuum case. Measurements are made at the off half cycle of during half-wave-rectified sine-wave heating of 3-mm-long 30-micron-diameter W probes positioned with 1-mm precision between 18 x 23-cm Al or Cu plates 7.6 cm apart. The results are presented graphically: potentials of up to + or 30 V are measured with accuracy + or - 0.4 V.

Cho, M. H.↗
NASA NTRS1985

The cold solar wind

From 3 to 10 percent of the time, the solar wind has a radial proton temperature between 15,000 K and 3500 K (the lowest recorded temperature). This 'cold' component shows some very important features that make it worthy of special study. It shows a temperature dependence on helicentric distance that is nearly adiabatic. When extrapolated back to 3 R(s), assuming adiabatic cooling, the resulting temperature for this cold component is in good agreement with coronal temperatures near the sonic point. Most importantly, the proton velocities and densities associated with this cold component match those predicted by solar wind models that do not incorporate significant wave heating. It is concluded that this is one solar wind component that fits well with appropriate models.

Freeman, J. W.↗