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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Surface energy fluxes at Central Florida during the convection and precipitation electrification experiment

One of the objectives of CaPE is to better understand the convective process in central and south Florida during the warm season. The energy and moisture exchanges between the surface and the atmosphere are closely related to this process. Some recent studies have shown that the surface energy balance plays an important role in the climatic fields (Shukla and Mintz, 1982; Sud and Smith, 1985; Sato et. al, 1989). Surface energy fluxes and related surface processes such as evapotranspiration and sensible heat transfer directly effect the temperature, humidity, cloud formation and precipitation. For example, mesoscale circulation around a discontinuity in vegetation type were shown to be stronger with wet soil than with dry soil using an evapotranspiration model (Pinty et. al, 1989). In order to better describe the processes in the atmosphere at various scales and improve our ability of modeling and predicting weather related events, it is crucial to understand the mechanism of surface energy transfer in relation to atmospheric events. Surface energy flux measurements are required to fully understand the interactions between the atmosphere and the surface.

Nie, D.↗
NASA NTRS1977

Chatanika observations of the latitudinal structure of electric fields and particle precipitation on November 21, 1975

By using a new multiposition experimental procedure the incoherent scatter radar facility of Chatanika, Alaska, has been used to obtain detailed latitudinal structure of ion velocities and electric fields in the afternoon and midnight sectors during a period of moderate magnetic disturbance. In particular, the latitudinal and local time structure of the Harang discontinuity has been investigated. In agreement with other observations it is found that the convection flow direction changes from westward through south to eastward over a fairly wide local time range (1-2 hours), the highest latitudes displaying the widest region. The Harang discontinuity encounter is accompanied by an abrupt increase in electron precipitation, the most intense part being located slightly east of the center of the discontinuity. It is suggested that this injection is due to processes closely connected with the discontinuity region itself, rather than to a substorm-related energization.

Wedde, T.↗
DOE OSTI2022

Encapsulation of hygroscopic liquids via polymer precipitation in non-aqueous emulsions

Here, encapsulation of ionic liquids (ILs) and phase change materials (PCMs) can overcome limitations associated with bulk materials, e.g., slow mass transfer rates, high viscosities, or susceptibility to external environment. Single step soft-templated encapsulation methods commonly use interfacial polymerization for shell formation, with a multifunctional monomer in the continuous phase and another in the discontinuous phase, and thus do not give pristine core material. We posit that polymer precipitation onto emulsion droplets in non-aqueous emulsions could produce a robust shell without contamination of the core, ideal for the encapsulation of water-sensitive or water-miscible materials. Solutions of commodity polymers were added to the continuous phase of non-aqueous Pickering emulsions stabilized by alkylated graphene oxide (GO) nanosheets such that the change in solubility of the polymer led to formation of robust shells and the production of capsules that could be isolated. We demonstrate that a polymer precipitation approach can produce capsules with pristine core of the IL 1-ethyl-3-methylimidazolium hexafluorophosphate [Emim][PF 6 ] or the salt hydrate PCM magnesium nitrate hexahydrate (MNH) and shell of nanosheets and polystyrene, poly(methyl methacrylate), or polyethylene. The capsules are approximately 80 wt% [Emim][PF 6 ] or >90 wt% MNH, and the core can undergo multiple cycles of solidification and melting without leakage or destruction. This novel, single-step methodology provides a distinct advantage to access capsules with pristine core composition and is amenable to different core and shell, paving the way for tailoring capsule composition for desired applications.

36 MATERIALS SCIENCE↗
NASA NTRS1985

Fine structure and dynamics of the Harang discontinuity - An event study

Two rockets were launched simultaneously from the Andoya Rocket Range in northern Norway into and through a Harang discontinuity region during a small isolated substorm. Each was equipped with an array of instruments for monitoring ionospheric electric fields and auroral particles. Different sized rockets allowed both to traverse a range of 300 km while introducing altitude separations of up to 440 km, and separations between the feet of the magnetic field lines intersecting the payloads of up to 100 km. The data sets, coupled with multi-station ground-based observations, provide information on the structure and dynamics of the Harang discontinuity region. Two boundaries were encountered. The first electric field reversal was observed simultaneously by both payloads in a region of weak precipitation, while the second reversal was associated with an intense auroral band. Since an unambiguous interpretation of these data is not possible, two alternative scenarios are presented. In one the discontinuity becomes realigned during the flight following a decay in the activity. The second involves a triple cell convection system, possibly the result of an eddy in the flow.

Egeland, A.↗
NASA NTRS1993

Coupled land surface/hydrologic/atmospheric models

The topics covered include the following: prototype land cover characteristics data base for the conterminous United States; surface evapotranspiration effects on cumulus convection and implications for mesoscale models; the use of complex treatment of surface hydrology and thermodynamics within a mesoscale model and some related issues; initialization of soil-water content for regional-scale atmospheric prediction models; impact of surface properties on dryline and MCS evolution; a numerical simulation of heavy precipitation over the complex topography of California; representing mesoscale fluxes induced by landscape discontinuities in global climate models; emphasizing the role of subgrid-scale heterogeneity in surface-air interaction; and problems with modeling and measuring biosphere-atmosphere exchanges of energy, water, and carbon on large scales.

Pielke, Roger↗
DOE OSTI2021

An uncertainty-focused database approach to extract spatiotemporal trends from qualitative and discontinuous lake-status histories

Changes in lake status are often interpreted as palaeoclimate indicators due to their dependence on precipitation and evaporation. The Global Lake Status Database (GLSDB) has since long provided a standardised synopsis of qualitative lake status over the last 30,000 14C years. Potential sources of uncertainty however are not recorded in the GLSDB. Here we present an updated and improved relational-database framework that incorporates uncertainty in both chronology and the interpretation of palaeoenvironmental data. The database uses peer-reviewed palaeolimnological studies to produce a consensus on qualitative lake-status histories, whose chronologies are revised and standardized through the recalibration of radiocarbon dates and the application of Bayesian age-depth modelling for stratigraphic archives. Quantitative information on absolute water-level elevation is preserved if available from geomorphological sources. We also propose a new probabilistic analytical framework that accounts for these uncertainties to reconstruct synoptic, integrated environmental signals. The process is based on a Monte Carlo algorithm that iteratively samples individual lake-status histories within the limits of their uncertainties to produce many possible scenarios. We then use Recursively-Subtracted Empirical Orthogonal Function analysis to extract dominant patterns of lake-status variability from these scenarios. As a proof of concept, we apply this framework to 67 sites in eastern and southern Africa whose lake-status histories cover part of the late Pleistocene and/or Holocene. We show that, despite the sometimes large temporal and interpretation uncertainties, and the inclusion of highly discontinuous lake-status time series, identifying the major known millennial-scale climatic phases during the last 20,000 years is possible. Our framework was also able to identify an antiphased response between the lake basins in eastern and interior southern Africa to these changes. Here, we propose that our new database and methodology framework serves as a template for efficient lake-status data synthesis, encourages the incorporation of lake-status data in palaeoclimate syntheses, and expands the possibilities for the use of such data in the evaluation of climate models.

58 GEOSCIENCES↗
NASA NTRS1985

Electrodynamics of the westward traveling surge

It is shown that the global convection pattern, the ionospheric current, and the field-aligned current associated with the westward traveling surge in the asymptotic state can be modeled quantitatively as consequences of a blockage of the Hall current from closure in the magnetosphere via field-aligned currents. The conductivity is allowed to increase self-consistently with increasing upward field-aligned current in the model. This inclusion of the self-consistent enhanced ionospheric conductivity due to discrete auroral precipitations is found to generate a localized intense westward electrojet on the poleward side of the Harang discontinuity. The westward electrojet is also found to rotate counterclockwise, merging into the eastward electrojet around the leading edge of the surge. Thus the major features of the westward traveling surge can be reproduced reasonably well in the model.

Kan, J. R.↗
DOE OSTI2021

Geophysical and Environmental Monitoring Data, Lower Watershed, Teller Road Mile Marker 27, Seward Peninsula, Alaska, 2017-2019

This data set contains geophysical and environmental monitoring data acquired between September 2017 and 2019 at the lower Teller watershed, Seward Peninsula, Alaska. Geophysical data comprises processed resistivity data, acquired daily between Spring and Fall of 2018 and 2019, and a baseline measurement of Fall 2017. The environmental monitoring data comprises depth resolved, distributed soil moisture and soil temperature data. These measurements were obtained used Decagon 5TE sensors placed at 0.1 m, 0.2 m , 0.3 m, and 0.4 m depth. In addition, temperature data at 0.5 m, 1.0 m, and 1.5 m were acquired using Hobo temperature sensors. Data were collected to improve our understanding of the hydrological response of discontinuous permafrost systems, in particular focusing on multi-annual dynamics and short term disturbances, such as snowmelt or precipitation events. The electrical resistivity tomography (ERT) monitoring data are included as processed resistivity models, with model cells x dimension equal to the distance along the profile, and model z dimension being elevation. The start and end point of the transect are (UTM Zone 3N): E 454881.66 m, N 7178949.45 m, and E 454772.60, N 7178885.81. Locations of the soil moisture and temperature sensors are provided in the data package. This dataset is discussed in detail in the Uhlemann, S. et al 2021 paper listed in the references. This dataset includes one *.pdf user guide and 315 *.csv data files included within four zipped files.The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research.The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska.Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2010

A Modeling and Verification Study of Summer Precipitation Systems Using NASA Surface Initialization Datasets

One of the most challenging weather forecast problems in the southeastern U.S. is daily summertime pulse-type convection. During the summer, atmospheric flow and forcing are generally weak in this region; thus, convection typically initiates in response to local forcing along sea/lake breezes, and other discontinuities often related to horizontal gradients in surface heating rates. Numerical simulations of pulse convection usually have low skill, even in local predictions at high resolution, due to the inherent chaotic nature of these precipitation systems. Forecast errors can arise from assumptions within parameterization schemes, model resolution limitations, and uncertainties in both the initial state of the atmosphere and land surface variables such as soil moisture and temperature. For this study, it is hypothesized that high-resolution, consistent representations of surface properties such as soil moisture, soil temperature, and sea surface temperature (SST) are necessary to better simulate the interactions between the surface and atmosphere, and ultimately improve predictions of summertime pulse convection. This paper describes a sensitivity experiment using the Weather Research and Forecasting (WRF) model. Interpolated land and ocean surface fields from a large-scale model are replaced with high-resolution datasets provided by unique NASA assets in an experimental simulation: the Land Information System (LIS) and Moderate Resolution Imaging Spectroradiometer (MODIS) SSTs. The LIS is run in an offline mode for several years at the same grid resolution as the WRF model to provide compatible land surface initial conditions in an equilibrium state. The MODIS SSTs provide detailed analyses of SSTs over the oceans and large lakes compared to current operational products. The WRF model runs initialized with the LIS+MODIS datasets result in a reduction in the overprediction of rainfall areas; however, the skill is almost equally as low in both experiments using traditional verification methodologies. Output from object-based verification within NCAR s Meteorological Evaluation Tools reveals that the WRF runs initialized with LIS+MODIS data consistently generated precipitation objects that better matched observed precipitation objects, especially at higher precipitation intensities. The LIS+MODIS runs produced on average a 4% increase in matched precipitation areas and a simultaneous 4% decrease in unmatched areas during three months of daily simulations.

Jonathan L. Case↗
NASA NTRS1991

Advanced electromagnetic methods for aerospace vehicles

The Advanced Helicopter Electromagnetics is centered on issues that advance technology related to helicopter electromagnetics. Progress was made on three major topics: composite materials; precipitation static corona discharge; and antenna technology. In composite materials, the research has focused on the measurements of their electrical properties, and the modeling of material discontinuities and their effect on the radiation pattern of antennas mounted on or near material surfaces. The electrical properties were used to model antenna performance when mounted on composite materials. Since helicopter platforms include several antenna systems at VHF and UHF bands, measuring techniques are being explored that can be used to measure the properties at these bands. The effort on corona discharge and precipitation static was directed toward the development of a new two dimensional Voltage Finite Difference Time Domain computer program. Results indicate the feasibility of using potentials for simulating electromagnetic problems in the cases where potentials become primary sources. In antenna technology the focus was on Polarization Diverse Conformal Microstrip Antennas, Cavity Backed Slot Antennas, and Varactor Tuned Circular Patch Antennas. Numerical codes were developed for the analysis of two probe fed rectangular and circular microstrip patch antennas fed by resistive and reactive power divider networks.

Balanis, Constantine A.↗
DOE OSTI2020

Contrasting stream nitrate and sulfate response to recovery from experimental watershed acidification

Improvements in air quality have led to ecosystem recovery from acidic deposition, but the mechanisms and trajectories of this recovery are not fully understood. Here, we present long-term stream response and recovery data for paired watersheds at the Bear Brook Watershed in Maine (BBWM) during declining ambient SO 4 and NO 3 in precipitation. East Bear (EB) received ambient deposition from 1989 to 2018; West Bear (WB) received artificially elevated N+S from 1989 to 2016. The WB treatment was discontinued after 2016, the beginning of the recovery from both the experimental N+S and ambient decline. Stream SO 4 in WB gradually declined after the treatment ended, from ~147 µeq L -1 in 2010-16 to ~126 µeq L -1 in 2017-18. The declining S inputs induced desorption of SO 4 from soil phase surfaces, with stream loss far exceeding precipitation input. At the current rate of recovery, it will be many decades before the WB stream returns to pre-treatment SO 4 concentrations. In contrast, NO 3 is only weakly adsorbed in soil, and WB stream NO 3 concentrations rapidly declined from ~39 µeq L -1 in 2010-16 to ~5 µeq L -1 in 2017-18, comparable to the N-limited EB stream. The acid anions are strongly coupled to base cation chemistry in streams, and there was a distinct hysteretic response of Ca and Mg to the chronic acidification, as (Ca+Mg) increased rapidly during the initial years, followed by declining values due to depletion of the soil exchange complex. This 30-year monitoring study (1989-2019) provides insights into recovery mechanisms from acidic deposition and highlights the role of abiotic processes in soil that mediate nutrient cycling and retention. Finally, documenting the rapid response of N alongside the slower recovery for S identifies the temporal resolution necessary for other whole-watershed recovery studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Electrical monitoring of saline tracers to reveal subsurface flow pathways in a flat ditch-drained field

Time-lapse electrical resistivity imaging (ERI) combined with salt tracers can enhance our understanding of subsurface flow and transport in ditch-drained agroecosystems. In a nearly level field adjacent to a drainage ditch, we installed 192 electrodes in a 72-m2 plot along with five hydrometric stations to enable time-lapse ERI monitoring during storms. Immediately prior to a wintertime rainstorm, we applied 5 kg of KBr to a shallow trench located roughly 11 m upgradient from the ditch. Antecedent conditions prior to the storm were wet, assuring a hydrologically connected state that favored tracer dissolution and movement in the subsurface. We monitored the evolution of the tracer plume with ERI over a seven-day period. Four-dimensional (4D) delineation of precipitation and tracer transport using time-lapse ERI showed that the tracer plume moved preferentially downward through a discontinuity in the argillic horizon within the first 57 hrs. Over the following 79 hrs, the tracer plume exhibited steady, lateral movement towards the drainage ditch within a more permeable sandy horizon situated just below the argillic. A spatial moment analysis of logarithmic changes in conductivity in the sand layer revealed seepage velocities ranging from 0.0027 to 0.0482 m d-1; these values were positively correlated with hydraulic gradients, suggesting laminar flow processes typical of sandy aquifers. Increasing groundwater velocities with hydraulic gradients suggest that solute transfers from groundwater to ditch are likely to be faster in storms, especially during wet periods. Even so, predominantly slow lateral transport within the sandy horizon, even during storms, indicates that critical source areas of pollutant loss are likely within a few meters of the ditch.

Robinson, Judith L.↗
NASA NTRS2019

The Combined Radar-Radiometer Algorithm — GPM Version 06X

The primary motivation behind the Version 6X (V06X) Combined Radar-Radiometer Algorithm (CORRA) is to utilize high-sensitivity mode (HS) Ka-band data that had been moved to locations in the outer part of the GPM Dual-Frequency Precipitation Radar (DPR) swath on May 21, 2018. Presented at the Precipitation Measurement Missions (PMM) meeting are statistics of CORRA precipitation estimates across both the inner and outer portions of the DPR swath for the purpose of identifying potential discontinuities caused by the new HS data. Although none are found, further investigation reveals possible biases caused by assumptions regarding radar pulse attenuation within the ground clutter of the DPR.

Olson, Bill↗
NASA NTRS1984

Currents in the earth's magnetotail

Currents in the earth's magnetotail are detected with the plasma instrumentation on board the ISEE-1 spacecraft. Field-aligned currents directed into and out of the ionosphere are found in the boundary layer of the plasma sheet. Typical current densities are in the range of 5 x 10-9 to 5 x 10-8 A/m2. These currents are associated with the Region 1 current system that is observed previously at low altitudes. An intense current sheet is shown to exist at a discontinuity in convection electric fields during a period of great magnetic activity. Electron acceleration, similar to that for electron inverted-V precipitation regions at low altitudes, occurs in this current sheet. Examination of the plasma velocity distributions at a neutral-sheet crossing reveals that the neutral sheet current is carried by electrons and protons. The relative directions for the bulk flows of the proton and electron plasmas indicate that the first adiabatic invariant is not conserved for the protons, and quite possibly for the electrons also. These letter findings are in substantial agreement with a neutral sheet model for acceleration of charged particles in the presence of a weak electric field.

Frank, L. A.↗
NASA NTRS2015

A Linearized Prognostic Cloud Scheme in NASAs Goddard Earth Observing System Data Assimilation Tools

A linearized prognostic cloud scheme has been developed to accompany the linearized convection scheme recently implemented in NASA's Goddard Earth Observing System data assimilation tools. The linearization, developed from the nonlinear cloud scheme, treats cloud variables prognostically so they are subject to linearized advection, diffusion, generation, and evaporation. Four linearized cloud variables are modeled, the ice and water phases of clouds generated by large-scale condensation and, separately, by detraining convection. For each species the scheme models their sources, sublimation, evaporation, and autoconversion. Large-scale, anvil and convective species of precipitation are modeled and evaporated. The cloud scheme exhibits linearity and realistic perturbation growth, except around the generation of clouds through large-scale condensation. Discontinuities and steep gradients are widely used here and severe problems occur in the calculation of cloud fraction. For data assimilation applications this poor behavior is controlled by replacing this part of the scheme with a perturbation model. For observation impacts, where efficiency is less of a concern, a filtering is developed that examines the Jacobian. The replacement scheme is only invoked if Jacobian elements or eigenvalues violate a series of tuned constants. The linearized prognostic cloud scheme is tested by comparing the linear and nonlinear perturbation trajectories for 6-, 12-, and 24-h forecast times. The tangent linear model performs well and perturbations of clouds are well captured for the lead times of interest.

Precipitation↗
NASA NTRS1992

Energetic and magnetosheath energy particle signatures of the low-latitude boundary layer at low altitudes near noon

The low-latitude boundary layer (LBL) and its separation from the cusp have previously been identified using observations of particle precipitation at magnetosheath energies. Using S3-3 satellite observations, we have determined that these identifications can also be made from energetic particle observations on polar-orbiting satellites. It is found that the equatorward boundary of the LBL is identifiable as an approximately discontinuous decrease in 33-keV electron fluxes from low to high latitudes. Both the energetic ion and electron fluxes decrease discontinuously at the boundary between the LBL and the cusp or polar cap. A distinct LBL is nearly always identifiable in energetic particle measurements in the 10-14 MLT region when counting rates are statistically significant. The identifications obtained using the energetic particle measurements have been compared to those obtained using criteria developed by Newell and Meng (1988, 1989) for magnetosheath energy particle precipitation. In this way, we have evaluated the accuracy of both techniques and used the energetic particle measurements to supplement the identifications obtained using the Newell and Meng criteria. We propose that the Newell and Meng threshold on ion energy flux can be reduced by a factor of 6. This modification provides identification of the LBL for lower ion intensity levels than has previously been thought possible. Source, acceleration, and scattering processes have also been studied within and in the vicinity of the LBL. Observed trapped pitch angle distributions of energetic electrons imply that the LBL is at least partially on closed field lines. Strong scattering of energetic protons is found within and equatorward of the LBL and thus must occur at least partially along closed field lines. Field-aligned electron acceleration by parallel electric fields can be discerned within and poleward of the LBL, but a more detailed analysis is necessary for a statistical study. Conical ion acceleration was seen relatively frequently within the LBL and about half as often poleward of the LBL. Neither acceleration process could be identified anywhere equatorward of the LBL.

Roeder, J. L.↗
NASA NTRS1977

Auroral vector electric field and particle comparisons. I - Preliminary convection topology

Data obtained by Polar 3, launched from northern Norway January 27, 1974, are interpreted. The rocket, which traversed nearly 3 deg of latitude, crossed over a stable IBC II auroral arc in the positive bay region and continued north to a convection boundary which has been identified as the Harang discontinuity. Measurements of the complete electric field vector, of energetic electrons, and of auroral emissions were used to study the convection topology in the premagnetic midnight region. The inverted V nature of the electron precipitations at the convection boundary, compared with the lack of such structure over the arc which was within the positive bay region, is thought to indicate that auroral arcs are likely to be associated with inverted V type precipitation only at or poleward of convection boundaries and their eddy structures.

Maynard, N. C.↗
NASA NTRS2009

Examining the Impacts of High-Resolution Land Surface Initialization on Model Predictions of Convection in the Southeastern U.S.

One of the most challenging weather forecast problems in the southeastern U.S. is daily summertime pulse convection. During the summer, atmospheric flow and forcing are generally weak in this region; thus, convection typically initiates in response to local forcing along sea/lake breezes, and other discontinuities often related to horizontal gradients in surface heating rates. Numerical simulations of pulse convection usually have low skill, even in local predictions at high resolution, due to the inherent chaotic nature of these precipitation systems. Forecast errors can arise from assumptions within physics parameterizations, model resolution limitations, as well as uncertainties in both the initial state of the atmosphere and land surface variables such as soil moisture and temperature. For this study, it is hypothesized that high-resolution, consistent representations of surface properties such as soil moisture and temperature, ground fluxes, and vegetation are necessary to better simulate the interactions between the land surface and atmosphere, and ultimately improve predictions of local circulations and summertime pulse convection. The NASA Short-term Prediction Research and Transition (SPORT) Center has been conducting studies to examine the impacts of high-resolution land surface initialization data generated by offline simulations of the NASA Land Informatiot~ System (LIS) on subsequent numerical forecasts using the Weather Research and Forecasting (WRF) model (Case et al. 2008, to appear in the Journal of Hydrometeorology). Case et al. presents improvements to simulated sea breezes and surface verification statistics over Florida by initializing WRF with land surface variables from an offline LIS spin-up run, conducted on the exact WRF domain and resolution. The current project extends the previous work over Florida, focusing on selected case studies of typical pulse convection over the southeastern U.S., with an emphasis on improving local short-term WRF simulations over the Mobile, AL and Miami, FL NWS county warning areas. Future efforts may involve examining the impacts of assimilating remotely-sensed soil moisture data, and/or introducing weekly greenness vegetation fraction composites (as opposed to monthly climatologies) into ol'fline NASA LIS runs. Based on positive impacts, the offline LIS runs could be transitioned into an operational mode, providing land surface initialization data to NWS forecast offices in real time.

Case, Jonathan L.↗