Search NASA⌕ Search

SEARCH · Search NASA

Results for “Environmental variabilities”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Assessment of historical and projected segments of US and world civil and military rotorcraft markets, 1960 - 1990

The geographic climatic, political, economic and demographic environment of 75 countries was analyzed with respect to helicopter procurement history and usage. Key environmental indicators which are variables were projected into strengths and weaknesses of U.S. technology are reviewed. The civil market sensitivity to new technology is forecast with selected premises as to vehicle life, noise standards, fuel costs, GNP expansion and traffic growth. The forecast is based on a scenario of helicopter technology improvements resulting in increased size and performance.

Yates, W. J.↗
NASA NTRS1981

A synoptic analysis of the first AVE-SESAME '79 period

Key features of a severe convection observed during April 10-11, 1979 as part of the Atmospheric Variability Experiment-Severe Environmental Storms and Mesoscale Experiment (AVE-SESAME) are examined. Three-hourly rawinsonde readings from 23 stations were taken, and vertical motion and divergence parameters are considered. The data were converted into a 127 km grid at the surface, and at 50 mb intervals from 900 mb to 100 mb by an objective analysis scheme, while a kinematic method was used to compute vertical motion. A weak upper tropospheric short wave trough was found to propagate from New Mexico into the Texas panhandle, while a jet maximum propagated eastward. The development of a strong wind maximum over Oklahoma and Kansas was associated with a rapid increase in upper-level divergence and the development of a small-scale pressure perturbation in the Texas panhandle, as well as a low-level jet and convergence, which led to rapid changes over the Red River Valley, where stability was decreased.

Moore, J. T.↗
NASA NTRS1990

Fatigue crack propagation in aerospace aluminum alloys

This paper reviews fracture mechanics based, damage tolerant characterizations and predictions of fatigue crack growth in aerospace aluminum alloys. The results of laboratory experimentation and modeling are summarized in the areas of: (1) fatigue crack closure, (2) the wide range crack growth rate response of conventional aluminum alloys, (3) the fatigue behavior of advanced monolithic aluminum alloys and metal matrix composites, (4) the short crack problem, (5) environmental fatigue, and (6) variable amplitude loading. Remaining uncertainties and necessary research are identified. This work provides a foundation for the development of fatigue resistant alloys and composites, next generation life prediction codes for new structural designs and extreme environments, and to counter the problem of aging components.

Gangloff, R. P.↗
NASA NTRS1992

Factors controlling fluxes of volatile sulfur compounds in Sphagnum peatlands

Exchange of DMS and OCS between the surface of Sphagnum peatlands and the atmosphere were measured with dynamic (S-free sweep air) and static enclosures. DMS emission rates determined by both methods were comparable. The dynamic method provided positive OCS flux rates (emission) for measurements performed at sites containing Sphagnum. Conversely, data from the static method indicated that OCS was consumed from the atmosphere. Short and long-term impacts of increased S deposition on fluxes of volatile S compounds (VSC's) from Sphagnum peatlands were investigated in a poor fen (Mire 239) at the Experimental Lakes Area, Ontario, Canada. Additional experiments were conducted in a poor fen (Sallie's Fen in Barrington, NH, USA). At Mire 239, emissions of VSC's were monitored, before and after acidification, at control and experimental sections within two major physiographic areas of the mire (oligotrophic and minerotrophic). DMS was the predominant VSC released from Mire 239 and varied largely with time and space. Sulfur addition did not affect DMS emissions in a period of hours to a few days. DMS emissions in the experimental oligotrophic area of the mire was approximately 3-fold greater than in the control oligotrophic area, and approximately 10-fold greater than in the minerotrophic zones. These differences could be due to a combination of differences in types of vegetation, nutritional status, and S input. At Sallie's Fen, DMS fluxes were not significantly affected by sulfate amendments, while DMS and MSH concentrations increased greatly with time in the top 10 cm of the peat column. The major environmental factors controlling fluxes of DMS in a Sphagnum-dominated peatland were investigated in Sallie's Fen, NH. DMS emissions from the surface of the peatland varied greatly over 24 hours and seasonally. Temperature seemed to be the major environmental factor controlling these variabilities. Concentrations of dissolved VSC's varied with time and space throughout the fen. Dissolved DMS, MSH, and OCS in the surface of the water table were supersaturated with respect to their concentrations in the atmosphere. Sphagnum mosses did not appear to be a direct source of VSC's, however they increase transport of DMS from the peat surface to the atmosphere.

Demello, William Zamboni↗
NASA NTRS1992

Environmental factors controlling fluxes of dimethyl sulfide in a New Hampshire fen

The major environmental factors controlling fluxes of dimethyl sulfide (DMS) in a Sphagnum-dominated peatland were investigated in a poor fen in New Hampshire. DMS emissions from the surface of the peatland varied greatly over 24 hours and seasonally. Maximum DMS emissions occurred in summer with minima in the late fall. Temperature was the major environmental factor controlling these variabilities. There was also some evidence that the changes in water table height might have contributed to the seasonable variability in DMS emission. The influence of the water table was greater during periods of elevated temperature. DMS and MSH were the most abundant dissolved volatile sulfur compound (VSC) in the surface of the water table. Concentrations of dissolved VSC's varied with time and space throughout the fen. Dissolved MDS, MSH, and OCS in the surface of the water table were supersaturated with respect to their concentrations in the atmosphere suggesting that the peat surface was a source of VSC's in the peatland. VCS in peatlands seemed to be produced primarily by microbial processes in the anoxic surface layers of the peat rich in organic matter and inorganic sulfide. Sphagnum mosses were not a direct source of VSC's. However, they increased transport of DMS from the peat surface to the atmosphere.

Demello, William Zamboni↗
NASA NTRS2021

Assessing Cyanobacterial Frequency and Abundance at Surface Waters Near Drinking Water Intakes Across the United States

This study presents the first large-scale assessment of cyanobacterial frequency and abundance of surface water near drinking water intakes across the United States. Public water systems serve drinking water to nearly 90% of the United States population. Cyanobacteria and their toxins may degrade the quality of finished drinking water and can lead to negative health consequences. Satellite imagery can serve as a cost-effective and consistent monitoring technique for surface cyanobacterial blooms in source waters and can provide drinking water treatment operators information for managing their systems. This study uses satellite imagery from the European Space Agency’s Ocean and Land Colour Instrument (OLCI) spanning June 2016 through April 2020. At 300-m spatial resolution, OLCI imagery can be used to monitor cyanobacteria in 685 drinking water sources across 285 lakes in 44 states, referred to here as resolvable drinking water sources. First, a subset of satellite data was compared to a subset of responses (n = 84) submitted as part of the U.S. Environmental Protection Agency’s fourth Unregulated Contaminant Monitoring Rule (UCMR 4). These UCMR 4 qualitative responses included visual observations of algal bloom presence and absence near drinking water intakes from March 2018 through November 2019. Overall agreement between satellite imagery and UCMR 4 qualitative responses was 94% with a Kappa coefficient of 0.70. Next, temporal frequency of cyanobacterial blooms at all resolvable drinking water sources was assessed. In 2019, bloom frequency averaged 2% and peaked at 100%, where 100% indicated a bloom was always present at the source waters when satellite imagery was available. Monthly cyanobacterial abundances were used to assess short-term trends across all resolvable drinking water sources and effect size was computed to provide insight on the number of years of data that must be obtained to increase confidence in an observed change. Generally, 2016-2020 was an insufficient time period for confidently observing changes at these source waters; on average, a decade of satellite imagery would be required for observed environmental trends to outweigh variability in the data. However, five source waters did demonstrate a sustained short-term trend, with one increasing in cyanobacterial abundance from June 2016 to April 2020 and four decreasing.

remote sensing↗
NASA NTRSDate not supplied

Grand Valley Ecological Forecasting II: Forecasting Trends in Pinyon-Juniper and Sagebrush Habitat Relative to Wildfire, Drought, Beetle Disturbance, and Treatment Impact for Management Planning

Disturbances and landcover change in pinyon-juniper and sagebrush ecosystems are exacerbated by environmental conditions such as variability in climate characteristics. Our DEVELOP team partnered with the National Park Service (NPS) in Colorado National Monument and the Bureau of Land Management (BLM) in McInnis Canyons and Dominguez-Escalante National Conservation Areas to investigate disturbances to land cover. NPS partners were interested in identifying areas at risk of pinyon-juniper die-off or encroachment by invasive species. The BLM partners prioritized identifying areas suitable for fire reduction and prevention treatment. To address these concerns, we forecasted landcover change in the Grand Valley region of Colorado using NASA Earth observation data from Landsat 5 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper (ETM+), Landsat 8 Operational Land Imager (OLI), and Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra and Aqua. We collected and analyzed these data in conjunction with Term I of this project. We found that the primary drivers of forecasted landcover change in the study area were aspect and elevation. Our forecasted land cover maps, created using the Idrisi TerrSet Land Change Modeler, indicated that by 2040, ecosystems within partner management areas will likely see tree encroachment on shrublands. These maps addressed the needs of our partners by showing potential habitat suitability trends, which will inform management planning.

Bill Curtiss↗
NASA NTRS2022

Grand Valley Ecological Forecasting II: Forecasting Trends in Pinyon-Juniper and Sagebrush Habitat Relative to Wildfire, Drought, Beetle Disturbance, and Treatment Impact for Management Planning

Disturbances and landcover change in pinyon-juniper and sagebrush ecosystems are exacerbated by environmental conditions such as variability in climate characteristics. Our DEVELOP team partnered with the National Park Service (NPS) in Colorado National Monument and the Bureau of Land Management (BLM)in McInnis Canyons and Dominguez-Escalante National Conservation Areas to investigate disturbances to land cover. NPS partners were interested in identifying areas at risk of pinyon-juniper die-off or encroachment by invasive species. The BLM partners prioritized identifying areas suitable for fire reduction/prevention treatment. To address these concerns, we forecasted landcover change in the Grand Valley region of Colorado using NASA Earth observation data from Landsat 5 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper (ETM+), Landsat 8 Operational Land Imager (OLI), and Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra and Aqua. We collected and analyzed these data in conjunction with Term I of this project. We found that the primary drivers of forecasted landcover change in the study area were aspect and elevation. Our forecasted landcover change maps, created using the Idrisi TerrSet Land Change Modeler, addressed the needs of our partners by showing potential habitat suitability trends, which will inform management planning. Forecasted landcover maps indicated that by 2040, ecosystems within partner management areas will likely see tree encroachment on shrublands.

William Curtiss↗
DOE OSTI2022

Release Timing and Duration Control the Fate of Photolytic Compounds in Stream-Hyporheic Systems

Predicting environmental fate requires an understanding of the underlying, spatiotemporally variable interaction of transport and transformation processes. Photolytic compounds, for example, interact with both time-variable photolysis and the perennially dark hyporheic zone, generating potentially unexpected dynamics that arise from time-variable reactivity. This interaction has been found to significantly impact environmental fate but is commonly oversimplified in predictive models. Our primary objective was to explore how time-variable photolysis and hyporheic storage interact across a range of photolysis rates to control the fate and transport of photolytic solutes in stream-hyporheic systems. In this study, we released a photolytic compound in a natural system at different times of day and simulated variable release timing and durations of photolytic compounds spanning half-lives ranging from about 2 min to 900 hr. To contextualize these results, we simulated five photolytic compounds with varied half-lives to systematically study the interaction between release timing, duration, and reactivity. We found that the environmental fate and transport of photolytic compounds are highly variable as a function of release timing, which controls when, where, and for how long solute is stored in the hyporheic zone or exposed to in-channel photolysis. Finally, this knowledge can be used to improve predictions for photolytic compounds or assess potential impacts for an anticipated discharge or treatment.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1973

User's instructions for the cardiovascular Walters model

The model is a combined, steady-state cardiovascular and thermal model. It was originally developed for interactive use, but was converted to batch mode simulation for the Sigma 3 computer. The model has the purpose to compute steady-state circulatory and thermal variables in response to exercise work loads and environmental factors. During a computer simulation run, several selected variables are printed at each time step. End conditions are also printed at the completion of the run.

Croston, R. C.↗
DOE OSTI2024

Perennializing marginal croplands: going back to the future to mitigate climate change with resilient biobased feedstocks

Managing annual row crops on marginally productive croplands can be environmentally unsustainable and result in variable economic returns. Incorporating perennial bioenergy feedstocks into marginally productive cropland can engender ecosystem services and enhance climate resiliency while also diversifying farm incomes. We use one of the oldest bioenergy-specific field experiments in North America to evaluate economically and environmentally sustainable management practices for growing perennial grasses on marginal cropland. This long-term field trial called 9804 was established in 1998 in eastern Nebraska and compared the productivity and sustainability of corn (Zea mays L.)—both corn grain and corn stover—and switchgrass (Panicum virgatum L.) bioenergy systems under different harvest strategies and nitrogen (N) fertilizer rates. This experiment demonstrated that switchgrass, compared to corn, is a reliable and sustainable bioenergy feedstock. This experiment has been a catalyst for other bioenergy projects which have also expanded our understanding of growing and managing bioenergy feedstocks on marginal cropland. We (1) synthesize research from this long-term experiment and (2) provide perspective concerning both the knowledge gained from this experiment and knowledge gaps and how to fill them as well as the role switchgrass will play in the future of bioenergy.

09 BIOMASS FUELS↗
DOE OSTI2022

One Stomatal Model to Rule Them All? Toward Improved Representation of Carbon and Water Exchange in Global Models

Abstract Stomatal conductance schemes that optimize with respect to photosynthetic and hydraulic functions have been proposed to address biases in land‐surface model (LSM) simulations during drought. However, systematic evaluations of both optimality‐based and alternative empirical formulations for coupling carbon and water fluxes are lacking. Here, we embed 12 empirical and optimization approaches within a LSM framework. We use theoretical model experiments to explore parameter identifiability and understand how model behaviors differ in response to abiotic changes. We also evaluate the models against leaf‐level observations of gas‐exchange and hydraulic variables, from xeric to wet forest/woody species spanning a mean annual precipitation range of 361–3,286 mm yr −1 . We find that models differ in how easily parameterized they are, due to: (a) poorly constrained optimality criteria (i.e., resulting in multiple solutions), (b) low influence parameters, (c) sensitivities to environmental drivers. In both the idealized experiments and compared to observations, sensitivities to variability in environmental drivers do not agree among models. Marked differences arise in sensitivities to soil moisture (soil water potential) and vapor pressure deficit. For example, stomatal closure rates at high vapor pressure deficit range between −45% and +70% of those observed. Although over half the new generation of stomatal schemes perform to a similar standard compared to observations of leaf‐gas exchange, two models do so through large biases in simulated leaf water potential (up to 11 MPa). Our results provide guidance for LSM development, by highlighting key areas in need for additional experimentation and theory, and by constraining currently viable stomatal hypotheses.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Coastal Sea Level Observations Record the Twentieth-Century Enhancement of Decadal Climate Variability

Changes in the amplitude of decadal climate variability over the twentieth century have been noted, with most evidence derived from tropical Pacific sea surface temperature records. However, the length, spatial coverage, and stability of most instrumental records are insufficient to robustly identify such nonstationarity, or resolve its global spatial structure. Here, it is found that the long-term, stable, observing platform provided by tide gauges reveals a dramatic increase in the amplitude and spatial coherence of decadal (11–14-yr period) coastal sea level (ζ) variability between 1960 and 2000. During this epoch, western North American ζ was approximately out of phase with ζ in Sydney, Australia, and led northeastern U.S. ζ by approximately 1–2 years. The amplitude and timing of changes in decadal ζ variability in these regions are consistent with changes in atmospheric variability. Specifically, central equatorial Pacific wind stress and Labrador Sea heat flux are highly coherent and exhibit contemporaneous, order-of-magnitude increases in decadal power. These statistical relationships have a mechanistic underpinning: Along the western North American coastline, equatorial winds are known to drive rapidly propagating ζ signals along equatorial and coastal waveguides, while a 1–2-yr lag between Labrador Sea heat fluxes and northeastern United States ζ is consistent with a remotely forced, buoyancy-driven, mechanism. Tide gauges thus provide strong independent support for an increase in interbasin coherence on decadal time scales over the second half of the twentieth century, with implications for both the interpretation and prediction of climate and sea level variability.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Evaluation of short-term initial performance of a “Molekule Air” portable air cleaner

The aim of this project was to evaluate and characterize the performance of a MOLEKULE AIR air cleaner unit. The testing protocol comprised the evaluation of an unused Molekule Air unit operating at maximum (“boost” setting) fan speed setting. The device was tested over initial short-term periods of 70-80 h of continuous operation. The tested air cleaner was challenged in separate experiments with a well-characterized mixture of volatile organic compounds (VOCs), and with ozone. All tests were performed at realistic pollutant levels in a 20-m 3 environmental stainless-steel chamber. Variables controlled and measured in this study included the chamber temperature, relative humidity, the composition and concentration of the challenge VOCs, and the concentrations of ozone. Potential formation of byproducts was also investigated to assess the overall performance.

47 OTHER INSTRUMENTATION↗
NASA NTRS1992

Plant growth modeling at the JSC variable pressure growth chamber - An application of experimental design

This paper describes the approach and results of an effort to characterize plant growth under various environmental conditions at the Johnson Space Center variable pressure growth chamber. Using a field of applied mathematics and statistics known as design of experiments (DOE), we developed a test plan for varying environmental parameters during a lettuce growth experiment. The test plan was developed using a Box-Behnken approach to DOE. As a result of the experimental runs, we have developed empirical models of both the transpiration process and carbon dioxide assimilation for Waldman's Green lettuce over specified ranges of environmental parameters including carbon dioxide concentration, light intensity, dew-point temperature, and air velocity. This model also predicts transpiration and carbon dioxide assimilation for different ages of the plant canopy.

Miller, Adam M.↗
NASA NTRS1982

System albedo as sensed by satellites - Its definition and variability

System albedo, an important climatological and environmental parameter, is considered. Some of the problems and assumptions involved in evaluating albedo from satellite data are discussed. Clear-sky and cloud albedos over the United Kingdom and parts of northwest Europe are treated. Consideration is given to the spectral, temporal, and spatial variations and the effect of averaging. The implications of these results for those using and archiving albedo values and for future monitoring of system albedo are discussed. Normalization is of especial importance since this correction alters many albedo values. The pronounced difference in spectral albedo of the two visible channels reemphasizes the problem of attempting to calculate integrated albedo values from meteorological satellite data. The assumption of isotropic reflection is seen to be invalid, hindering the computation of accurate albedo values.

Hughes, N. A.↗
NASA NTRS1976

Control of thermal balance by a liquid circulating garment based on a mathematical representation of the human thermoregulatory system

Test data and a mathematical model of the human thermoregulatory system were used to investigate control of thermal balance by means of a liquid circulating garment (LCG). The test data were derived from five series of experiments in which environmental and metabolic conditions were varied parametrically as a function of several independent variables, including LCG flowrate, LCG inlet temperature, net environmental heat exchange, surrounding gas ventilation rate, ambient pressure, metabolic rate, and subjective/obligatory cooling control. The resultant data were used to relate skin temperature to LCG water temperature and flowrate, to assess a thermal comfort band, to demonstrate the relationship between metabolic rate and LCG heat dissipation, and so forth. The usefulness of the mathematical model as a tool for data interpretation and for generation of trends and relationships among the various physiological parameters was also investigated and verified.

Kuznetz, L. H.↗
DOE OSTI2021

Ontology-Enriched Specifications Enabling Findable, Accessible, Interoperable, and Reusable Marine Metagenomic Datasets in Cyberinfrastructure Systems

Marine microbial ecology requires the systematic comparison of biogeochemical and sequence data to analyze environmental influences on the distribution and variability of microbial communities. With ever-increasing quantities of metagenomic data, there is a growing need to make datasets Findable, Accessible, Interoperable, and Reusable (FAIR) across diverse ecosystems. FAIR data is essential to developing analytical frameworks that integrate microbiological, genomic, ecological, oceanographic, and computational methods. Although community standards defining the minimal metadata required to accompany sequence data exist, they haven’t been consistently used across projects, precluding interoperability. Moreover, these data are not machine-actionable or discoverable by cyberinfrastructure systems. By making ‘omic and physicochemical datasets FAIR to machine systems, we can enable sequence data discovery and reuse based on machine-readable descriptions of environments or physicochemical gradients. In this work, we developed a novel technical specification for dataset encapsulation for the FAIR reuse of marine metagenomic and physicochemical datasets within cyberinfrastructure systems. This includes using Frictionless Data Packages enriched with terminology from environmental and life-science ontologies to annotate measured variables, their units, and the measurement devices used. This approach was implemented in Planet Microbe, a cyberinfrastructure platform and marine metagenomic web-portal. Here, we discuss the data properties built into the specification to make global ocean datasets FAIR within the Planet Microbe portal. We additionally discuss the selection of, and contributions to marine-science ontologies used within the specification. Finally, we use the system to discover data by which to answer various biological questions about environments, physicochemical gradients, and microbial communities in meta-analyses. This work represents a future direction in marine metagenomic research by proposing a specification for FAIR dataset encapsulation that, if adopted within cyberinfrastructure systems, would automate the discovery, exchange, and re-use of data needed to answer broader reaching questions than originally intended.

59 BASIC BIOLOGICAL SCIENCES↗