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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Eastern Equatorial Pacific Warming Delayed By Aerosols and Thermostat Response to Co2 Increase

Understanding the tropical Pacific response to global warming remains challenging. Here, we use a range of CMIP6 greenhouse warming experiments to assess the recent and future evolution of the equatorial Pacific east-west temperature gradient and corresponding Walker circulation. In abrupt CO2-increase scenarios many models generate an initial strengthening of this gradient resembling an ocean thermostat (OT), followed by a small weakening; other models generate an immediate weakening that becomes progressively stronger establishing a pronounced eastern equatorial Pacific (EP) warming pattern. The initial response in these experiments is a strong predictor for the future EP pattern simulated in both abrupt and realistic warming scenarios, but not in historical simulations showing no multi-model trend. The likely explanation is that the recent CO2-driven changes in the tropical Pacific are masked by aerosol effects and a potential OT-related delay, while the EP warming pattern will emerge as greenhouse gases overcome aerosol forcing.

Climate and Earth system modelling↗
NASA NTRSDate not supplied

Timing and Geochemical Evolution of Triassic and Jurassic Magmatism during the Break-up of Pangea along the Eastern North American Margin

While our understanding of continental break-up has seen dramatic advances over the past decades, the impact of syn-rift melt generation on the transition from mechanical stretching to seafloor spreading remains enigmatic. Early Mesozoic continental break-up along the U.S. Eastern North American Margin (ENAM) is characterized by protracted Triassic lithospheric stretching and syn-rift deposition interrupted by voluminous Central Atlantic Magmatic Province (CAMP) magmatism. This magmatic phase is followed by ~50 Myr of protracted rifting prior to steady-state seafloor spreading. Mesozoic magmatism recognized in outcrop and aeromagnetic datasets along the ENAM has been summarily attributed to CAMP, although extensive regional dikes preserved in the ENAM proximal rift domain remain largely undated. This study provides new constraints on the timing, duration, and geochemical evolution of syn-rift ENAM magmatism using in-situ apatite U-Pb geochronology and whole-rock geochemistry and integrates these data into a tectonic model. We present in-situ apatite U-Pb ages and whole-rock geochemical data for 16 diabase dikes and sills from NJ, PA, VA, NC, and SC. A Palisades Sill sample yielded an age of 201 ± 8 Ma and agrees with previous 40 Ar/39 Ar and U-Pb ages. Our new in-situ apatite U-Pb ages fall into three clusters and suggest three main pulses of magmatism along the ENAM, with an initial pulse of magmatism at ~205-195 Ma attributed to CAMP. Whole-rock geochemistry of this pulse shows silica (46-53 wt.%), total alkalis (2-4 wt.%), and enrichment of LREEs relative to HREEs, comparable to previously reported geochemical data for CAMP-related rocks along the ENAM. A second magmatic pulse occurred between ~181-175 Ma and shows slightly higher silica and total alkalis, compared to the older CAMP-age phase. The third pulse between ~166-145 Ma generally shows slightly higher silica and total alkalis. LOI and Sr/Yb values of the two younger pulses are similar to CAMP-age samples suggesting no post-crystallization alteration. These new data demonstrate long-lived syn-rift off-axis magmatism persisted ~50 Myr after the onset of CAMP. This post-CAMP off-axis magmatism is likely related to slow magma-limited spreading during the protracted transition to symmetric seafloor spreading along the ENAM.

Z. Foster-Baril↗
NASA NTRS2023

Changing Nature of High-Impact Snowfall Events in Eastern North America

Snowstorms cause substantial disruption in the eastern United States and Canada each winter. While reductions in annual snowfall are projected over most of this region due to anthropogenic global warming, daily snowfall extremes that have the greatest impact may not decrease in the same manner. We examine changes to two extreme snowfall metrics: the 95th percentile of daily snowfall (SF95, cm) and the number of events during which 10% of the mean annual snowfall is exceeded during a single day (TC10, events yr−1). We explore changes to these metrics in two ensembles of the fifth-generation Canadian Regional Climate Model (CRCM5), including four 0.22° ( ≈ 25 km) simulations driven by different coupled general circulation models as well as the higher-resolution (0.11°, ≈ 12 km) ClimEx ensemble, driven by 50 members of a large initial-condition ensemble of one global model. We find that while mean annual snowfall is projected to decrease over our domain, SF95 is projected to remain relatively constant, suggesting that the most extreme daily snowfalls currently observed are likely to occur even in a warmer future climate. The region of the largest TC10 values exhibits a northward shift, with a larger percentage of annual snowfall occurring during a few large events along the U.S.-Canada border. These projected changes to the nature of snowfall events may have important socioeconomic consequences in this densely populated region of North America.

heavy snow↗
NASA NTRS2023

Emission Factors for Crop Residue and Prescribed Fires in the Eastern US during FIREX-AQ

Agricultural and prescribed burning activities emit large amounts of trace gases and aerosols on regional to global scales. We present a compilation of emission factors (EFs) and emission ratios (ERs) from the eastern portion of the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign in 2019 in the United States, which sampled burning of crop residues and other prescribed fire fuels. FIREX-AQ provided comprehensive chemical characterization of 53 crop residue and 22 prescribed fires. Crop residues burned at different modified combustion efficiencies (MCE), with corn residue burning at higher MCE than other fuel types. Prescribed fires burned at lower MCE (<0.90) which is typical, while grasslands burned at lower MCE (0.90) than normally observed due to moist, green, growing season fuels. Most non-methane volatile organic compounds (NMVOCs) were significantly anticorrelated with MCE except for ethanol and NMVOCs that were measured with less certainty. We identified 23 species where crop residue fires differed by more than 50% from prescribed fires at the same MCE. Crop residue EFs were greater for species related to agricultural chemical use and fuel composition as well as oxygenated NMVOCs possibly due to the presence of metals such as potassium. Prescribed EFs were greater for monoterpenes (5×). FIREX-AQ crop residue average EFs generally agreed with the previous agricultural fire study in the US but had large disagreements with global compilations. FIREX-AQ observations show the importance of regionally-specific and fuel-specific EFs as first steps to reduce uncertainty in modeling the air quality impacts of fire emissions.

air quality↗
DOE OSTI2014

Eastern Renewable Generation Integration Study Solar Dataset (Presentation)

The National Renewable Energy Laboratory produced solar power production data for the Eastern Renewable Generation Integration Study (ERGIS) including "real time" 5-minute interval data, "four hour ahead forecast" 60-minute interval data, and "day-ahead forecast" 60-minute interval data for the year 2006. This presentation provides a brief overview of the three solar power datasets.

14 SOLAR ENERGY↗
DOE OSTI2015

Building on the Iran Deal: Steps Toward a Middle Eastern Nuclear-Weapon-Free Zone

Approved unanimously by the UN Security Council on July 20, the agreement, formally known as the Joint Comprehensive Plan of Action, aims "to ensure that Iran's nuclear program will be exclusively peaceful" and thus to reduce the risk of nuclear proliferation. Other states in the Middle East, especially Egypt and Saudi Arabia, are planning to establish their own nuclear power programs during the period that the Iran deal is expected to be in force. Furthermore, the Joint Comprehensive Plan of Action provides an unprecedented opportunity for an international effort to make progress toward a Middle Eastern nuclear-weapon-free zone, possibly as part of WMD-free zone in that region. In building on the foundation created by that agreement, the measures proposed here constitute the essential technical steps toward a nuclear-weapon-free zone. Although it is unlikely that such a zone can be established anytime soon, it should be possible to make progress on a number of the building blocks for it.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2016

Gas hydrate characterization from a 3D seismic dataset in the deepwater eastern Gulf of Mexico

Seismic stratigraphic features are delineated using principal component analysis of the band limited data at potential gas hydrate sands, and compared and calibrated with spectral decomposition thickness to constrain thickness in the absence of well control. Layers in the abyssal fan sediments are thinner than can be resolved with 50 Hz seismic and thus comprise composite thin-bed reflections. Amplitude vs frequency analysis are used to indicate gas and gas hydrate reflections. Synthetic seismic wedge models show that with 50Hz seismic data, a 40% saturation of a Plio Pleistocene GoM sand in the hydrate stability zone with no subjacent gas can produce a phase change (negative to positive) with a strong correlation between amplitude and hydrate saturation. The synthetic seismic response is more complicated if the gas hydrate filled sediments overlie gassy sediments. Hydrate (or gas) saturation in thin beds enhances the amplitude response and can be used to estimate saturation. Gas hydrate saturation from rock physics, amplitude, and frequency analysis is compared to saturation derived from inversion at several interpreted gas hydrate accumulations in the eastern Gulf of Mexico.

gas hydrate↗