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At least 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Elemental abundances in corotating events

Large, persistent solar-wind streams in 1973 and 1974 produced corotating interaction regions which accelerated particles to energies of a few MeV/nucleon. The proton to helium ratio (H/He) was remarkably constant at a value (22 + or 5) equal to that in the solar wind (21 + or - 3), suggesting that particles were being accelerated directly out of the solar wind. Preliminary results were presented from a similar study approximately 11 years (i.e., one solar cycle) later. Corotating events have been identified by surveying the solar wind data, energetic particle time-histories and anisotropies. This data was all obtained from the ISEE-3/ICE spacecraft. These events also show H/He ratios similar to that in the solar wind. It is flund that in these cases there is evidence for H/He ratios which are significantly different from that of the solar wind but which are consistent with the range of values found in solar flare events.

Vonrosenvinge, T. T.↗
NASA NTRS1986

Elemental abundances in corotating events

Large, persistent solar-wind streams in 1973 and 1974 produced corotating interaction regions which accelerated particles to energies of a few MeV/nucleon. The proton to helium ratio (H/He) reported was remarkably constant at a value (22 + or - 5) equal to that in the solar wind (32 + or - 3), suggesting that particles were being accelerated directly out of the solar wind. Preliminary results from a similar study approximately 11 years (i.e., one solar cycle) later are reported. Corotating events were identified by surveying the solar wind data, energetic particle time-histories and anisotropies. This data was all obtained from the ISEE-3/ICE spacecraft. These events also show H/He ratios similar to that in the solar wind. In addition, other corotating events were examined at times when solar flare events could have injected particles into the corresponding corotating interaction regions. It was found that in these cases there is evidence for H/He ratios which are significantly different from that of the solar wind but which are consistent with the range of values found in solar flare events.

Vonrosenvinge, T. T.↗
NASA NTRS1988

Porous wind tunnel corrections for counterrotation propeller testing

Wind tunnel interference corrections have direct impact on measured propeller efficiency. A systematic series of wind tunnel tests was done in the porous-wall NASA Lewis 8- by 6-Foot Wind Tunnel to determine the wind tunnel interference corrections to the NASA Lewis counterrotation propeller test data. The test results were compared with calculations from a potential flow code to determine the interference corrections. At a Mach number of 0.8, the interference corrections resulted in a -0.008 Mach number correction which reduced the counterrotation propeller net efficiency data by 0.46 percent at the reduced Mach number. Additional wind tunnel tests were done to measure the effect of propeller thrust on wind tunnel wall interference. No wall interference corrections due to propeller thrust were found necessary for the high speed counterrotation propeller data obtained in the porous wall NASA Lewis 8- by 6-Foot Wind Tunnel.

Stefko, George L.↗
NASA NTRS1988

Porous wind tunnel corrections for counterrotation propeller testing

Wind tunnel interference corrections have direct impact on measured propeller efficiency. A systematic series of wind tunnel tests was done in the porous-wall NASA Lewis 8- by 6-Foot Wind Tunnel to determine the wind tunnel interference corrections to the NASA Lewis counterrotation propeller test data. The test results were compared with calculations from a potential flow code to determine the interference corrections. At a Mach number of 0.8, the interference corrections resulted in a -0.008 Mach number correction which reduced the counterrotation propeller net efficiency data by 0.46 percent at the reduced Mach number. Additional wind tunnel tests were done to measure the effect of propeller thrust on wind tunnel wall interference. No wall interference corrections due to propeller thrust were found necessary for the high speed counterrotation propeller data obtained in the porous wall NASA Lewis 8- by 6-Foot Wind Tunnel.

Stefko, George L.↗
NASA NTRS2000

The Breath of Planet Earth: Atmospheric Circulation. Assimilation of Surface Wind Observations

Differences in air pressure are a major cause of atmospheric circulation. Because heat excites the movement of atoms, warm temperatures cause, air molecules to expand. Because those molecules now occupy a larger space, the pressure that their weight exerts is decreased. Air from surrounding high-pressure areas is pushed toward the low-pressure areas, creating circulation. This process causes a major pattern of global atmosphere movement known as meridional circulation. In this form of convection, or vertical air movement, heated equatorial air rises and travels through the upper atmosphere toward higher latitudes. Air just above the equator heads toward the North Pole, and air just below the equator moves southward. This air movement fills the gap created where increased air pressure pushes down cold air. The ,cold air moves along the surface back toward the equator, replacing the air masses that rise there. Another influence on atmospheric. circulation is the Coriolis force. Because of the Earth's rotation, large-scale wind currents move in the direction of this axial spin around low-pressure areas. Wind rotates counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. just as the Earth's rotation affects airflow, so too does its surface. In the phenomenon of orographic lifting, elevated topographic features such as mountain ranges lift air as it moves up their surface.

Atlas, Robert↗
NASA NTRS2008

Relationship of Interplanetary Shock Micro and Macro Characteristics: A Wind Study

The non-linear least squared MHD fitting technique of Szabo 11 9941 has been recently further refined to provide realistic confidence regions for interplanetary shock normal directions and speeds. Analyzing Wind observed interplanetary shocks from 1995 to 200 1, macro characteristics such as shock strength, Theta Bn and Mach numbers can be compared to the details of shock micro or kinetic structures. The now commonly available very high time resolution (1 1 or 22 vectors/sec) Wind magnetic field data allows the precise characterization of shock kinetic structures, such as the size of the foot, ramp, overshoot and the duration of damped oscillations on either side of the shock. Detailed comparison of the shock micro and macro characteristics will be given. This enables the elucidation of shock kinetic features, relevant for particle energization processes, for observations where high time resolution data is not available. Moreover, establishing a quantitative relationship between the shock micro and macro structures will improve the confidence level of shock fitting techniques during disturbed solar wind conditions.

Szabo, Adam↗
NASA NTRS2002

Satellite-Based Assessment of Sediment Transport, Distribution and Resuspension Associated with the Atchafalaya River Discharge Plume

Tbe Atchafalaya River discharges over 80 x 10(exp 6) tons of sediment annually onto the broad shallow continental shelf of central and western Louisiana. Satellite imagery from the NOAA AVHRR and Terra MODIS are used in this paper to quantify suspended sediment concentrations and to assess sediment transport processes along the Louisiana shelf under varying conditions of river discharge and wind forcing. The image data reveal the maim sources of sediment, direction of transport amd regional extent of wind-wave resuspension. The prevailing easterly winds transport much of the suspended sediments westward toward the Chernier Plain in a well-defined mud stream. Westerly flow rates of 25-50 cm/s (21-43 km per day) have been measured, yielding a transit time of about 1.5-2.5 days from the mouth of Atchafalaya Bay to the Chernier Plain. Progradation rates along the Chernier Plain coast reach 50 m per year. The westward-flowing Atchafalaya "mud stream" is rapidly disrupted by westerly winds and northerly winds, which accompany frequent winter storms and less frequent tropical storms or hurricanes. During these events, the coastal current reverses and sediments are rapidly transported out of Atchafalaya Bay and offshore where substantial sedimentary deposits can also be found. Offshore sediment fluxes during storm events, in combination with wind-wave resuspension, can result in surface sediment "plumes" extending 70 km offshore and 150 km alongshore. Field measurements of suspended sediment concentrations, current and wind velocities, and directions are used to assess sediment transport processes on the shelf. These combined processes are extending the pro-delta deposits of the Atchafalaya-Wax Lake delta complex far onto the continental shelf and supplying sediments for a renewal era of progradation along tbe downdrift Chernier Plain coast.

Walker, Nan↗
DOE OSTI2025

Influence of Lake Ice Biases in Reanalysis Data on Downscaled Climate Simulations over the Great Lakes Region

This data package contains observation-based and model-simulated datasets (all provided in NetCDF format) for evaluating how wintertime lake-ice representation affects regional weather and climate over the Laurentian Great Lakes (freshwater lake ecosystem) during the high–ice-cover winter of 2009. The observational component includes: (1) Stage IV gridded precipitation at 4 km, hourly resolution for January–February 2009 over the Great Lakes region (radar–gauge multisensor precipitation analyses); (2) Great Lakes Surface Environmental Analysis (GLSEA) satellite-derived lake-ice coverage at 1.3 km, daily resolution for the 2009 winter months, providing ice coverage over Lakes Superior, Michigan, Huron, Erie, and Ontario; and (3) in situ measurements at the Standard Rock site on Lake Superior from the Great Lakes Evaporation Network (GLEN) at hourly resolution, including near-surface atmospheric variables and sensible and latent heat fluxes (air–lake exchange) at a fixed point location. The modeling component provides corresponding fields from two simulations, both archived at 4 km, hourly resolution: a standalone Weather Research Forecasting model (WRF) run driven by the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5 (ERA5), and a two-way coupled model using WRF and the Finite Volume Community Ocean Model (WRF-FVCOM, a 3-D hydrodynamic lake model). These outputs include variables relevant to air–lake interaction and lake-effect processes (e.g., near-surface temperature, humidity, wind, precipitation, and surface turbulent fluxes), enabling direct comparison with the observational datasets. Users can analyze and visualize these NetCDF files with common tools such as Python (e.g., xarray, netCDF4, numpy, pandas), NCO/CDO, Panoply, or ncview; NetCDF variables can also be converted to other formats (e.g., CSV, GeoTIFF) using these utilities.

EARTH SCIENCE > ATMOSPHERE > ATMOSPHERIC TEMPERATU↗
DOE OSTI2020

Test of a Novel, Commercial-Scale Wave Energy Direct-Drive Rotary Power Take-Off at the NREL National Wind Technology Center (CRADA CRD-14-571 Final Report)

The National Renewable Energy Laboratory (NREL) will work with Columbia Power Technologies [C-Power] to support work under US DOE DE-EE-0006399, “Build and Test of a Novel, Commercial-Scale Wave Energy Direct-Drive Rotary Power Take-Off Under Realistic Open-Ocean Conditions.” Work will include a review of their design for a novel wave energy direct drive generator. After review, the system will be prototyped and tested in the NREL National Wind Technology Center (NWTC) 5MW dynamometer and data will be recorded and analyzed. Conclusions from data analysis will be used to improve the design prior to completing a version of the system for ocean deployment. Additionally, NREL will work with Columbia Power Technologies [C-Power] to quantify the system levelized cost of energy (LCOE) and analyze the system in agreement with US DOE System Performance Advancement (SPA) goals 1 and 2.

16 TIDAL AND WAVE POWER↗
NASA NTRS1985

Development of large, horizontal-axis wind turbines

A program to develop large, horizontal-axis wind turbines is discussed. The program is directed toward developing the technology for safe, reliable, environmentally acceptable large wind turbines that can generate a significant amount of electricity at costs competitive with those of conventional electricity-generating systems. In addition, these large wind turbines must be fully compatible with electric utility operations and interface requirements. Several ongoing projects in large-wind-turbine development are directed toward meeting the technology requirements for utility applications. The machines based on first-generation technology (Mod-OA and Mod-1) successfully completed their planned periods of experimental operation in June, 1982. The second-generation machines (Mod-2) are in operation at selected utility sites. A third-generation machine (Mod-5) is under contract. Erection and initial operation of the Mod-5 in Hawaii should take place in 1986. Each successive generation of technology increased reliability and energy capture while reducing the cost of electricity. These advances are being made by gaining a better understanding of the system-design drivers, improving the analytical design tools, verifying design methods with operating field data, and incorporating new technology and innovative designs. Information is given on the results from the first- and second-generation machines (Mod-OA, - 1, and -2), the status of the Department of Interior, and the status of the third-generation wind turbine (Mod-5).

Baldwin, D. H.↗
NASA NTRS2007

Lidar and Mission Parameter Trade Study of Space-Based Coherent Wind Measurement Centered on NASA's 2006 GWOS Wind Mission Study Parameters

The global measurement of vertical profiles of horizontal vector winds has been highly desired for many years by NASA, NOAA and the Integrated Program Office (IPO) implementing the National Polar-orbiting Operational Environmental Satellite Systems (NPOESS). Recently the global wind mission was one of 15 missions recommended to NASA by the first ever NRC Earth Sciences Decadal Survey. Since before 1978, the most promising method to make this space-based measurement has been pulsed Doppler lidar. The favored technology and technique has evolved over the years from obtaining line-of-sight (LOS) wind profiles from a single laser shot using pulsed CO2 gas laser technology to the current plans to use both a coherent-detection and direct-detection pulsed Doppler wind lidar systems with each lidar employing multiple shot accumulation to produce an LOS wind profile. The idea of using two lidars (hybrid concept) entails coherent detection using the NASA LaRC-developed pulsed 2-micron solid state laser technology, and direct detection using pulsed Nd:YAG laser technology tripled in frequency to 355 nm wavelength.

Kavaya, Michael J.↗
NASA NTRS1990

Triton's streaks as windblown dust

Explanations for the surface streaks observed by Voyager 2 on Triton's southern hemisphere are discussed. It is shown that, despite Triton's tenuous atmosphere, low-cohesion dust trains with diameters of about 5 micron or less may be carried into suspension by aeolian surface shear stress, given expected geostrophic wind speeds of about 10 m/s. For geyser-like erupting dust plumes, it is shown that dust-settling time scales and expected wind velocities can produce streaks with length scales in good agreement with those of the streaks. Thus, both geyserlike eruptions or direct lifting by surface winds appear to be viable mechanisms for the origin of the streaks.

Sagan, Carl↗
NASA NTRS2023

Multi-Spacecraft Observations of Shocklets at an Interplanetary Shock

Interplanetary (IP) shocks are fundamental building blocks of the heliosphere, and the possibility to observe them in situ is crucial to address important aspects of energy conversion for a variety of astrophysical systems. Steepened waves known as shocklets are known to be important structures of planetary bow shocks, but they are very rarely observed related to IP shocks. We present here the first multi-spacecraft observations of shocklets observed by upstream of an unusually strong IP shock observed on 3 No v ember 2021 by several spacecraft at L1 and near-Earth solar wind. The same shock was detected also by radially aligned Solar Orbiter at 0.8 AU from the Sun, but no shocklets were identified from its data, introducing the possibility to study the environment in which shocklets developed. The Wind spacecraft has been used to characterize the shocklets, associated with pre-conditioning of the shock upstream by decelerating incoming plasma in the shock normal direction. Finally, using the Wind observations together with ACE and DSCOVR spacecraft at L1, as well as THEMIS B and THEMIS C in the near-Earth solar wind, the portion of interplanetary space filled with shocklets is addressed, and a lower limit for its extent is estimated to be of about 110 R E in the shock normal direction and 25 R E in the directions transverse to the shock normal. Using multiple spacecraft also reveals that for this strong IP shock, shocklets are observed for a large range of local obliquity estimates (9° –64°).

plasmas↗
NASA NTRSDate not supplied

Aeroacoustic Study of a Subscale Large Civil Transport (STAR) Model – Part 1: Simulations

Results from a computational aeroacoustic study of the Subsonic Transport Aeroacoustic Research (STAR) model are presented. The model, a 26%-scale semispan Boeing 777-200 aircraft, was an inceptive configuration in a comprehensive simulation campaign to accurately predict the airframe noise of a full-scale, large civil transport during landing. The lengthy process of obtaining a high-fidelity, CFD-ready, vetted, digital representation of the model is described in detail. The simulations were performed with the STAR model installed in the NASA Ames 40- by 80-foot full-scale wind tunnel to enable direct comparisons with aerodynamic and acoustic measurements of the model, presented separately in Part 2 of the study. Two versions of the wind tunnel test section were considered. The entire test section was used to simulate the aerodynamic behavior of the model; an open-wall representation of the section was adopted during the acoustic simulations to eliminate wall reflections. To preserve the aerodynamic equivalency of the model for the two simulated tunnel configurations, the open-wall computations were executed at an angle-of-attack one degree higher than that of the corresponding closed-wall tunnel. The effect on aerodynamic behavior of several minor geometry alterations necessary to con-form the simulated to the tested model was assessed – the modifications considerably altered the strength and extent of a flow separation zone on the inboard segment of the flap. Also evaluated was the impact of spatial resolution on aerodynamic and acoustic characteristics of the model – in general, medium resolution was sufficient to establish convergence trends for averaged surface pressure behavior and proper localization of noise sources. After the aeroacoustic characteristics of the baseline configuration were predicted, a toboggan-shaped fairing designed to reduce main landing gear noise was evaluated computationally. Far-field noise spectra for the baseline and toboggan-equipped STAR model were calculated via a Ffowcs-Williams and Hawkings integral approach, with flow quantities on a permeable data surface enclosing the source regions used as input. Results from the simulations indicated that, while the fairing reduced gear noise in the near-field, it had a negligible effect on the far-field noise signature of the model. This trend agreed with previously published experimental results obtained during sub-scale, isolated gear tests and full-scale flight tests

airframe noise↗
NASA NTRS1998

Spaceborne Simulations of Two Direct-Detection Doppler Lidar Techniques

Direct-detection (or incoherent) lidar is now a proven technique for measuring winds in the atmosphere. Over the last few years, several types of direct-detection lidar have evolved. These methods rely on Fabry-Perot interferometers(also termed etalons) or other narrow-passband filters to provide the required spectral resolution. One method, now called the edge (EDG) technique, uses a sharply-sloping filter and measures changes in the filter transmission caused by Doppler shifting of the laser wavelength. A variation of the EDG method, called the double-edge (DEDG) technique, uses two filters. The molecular DEDG method was first demonstrated by Chanin et al. for stratospheric measurements and more recently Korb et al. successfully demonstrated the aerosol DEDG through the troposphere. A second method, here termed the multi-channel (MC) technique, measures Doppler shifts by observing angular displacement of a Fabry-Perot fringe in a spatially resolving detector. The EDG technique thus employs the Fabry-Perot to convert the frequency shift into an amplitude signal, while the MC technique uses the Fabry-Perot to resolve the spectral signature which is then fitted to determine the centroid. The focus of this presentation is on the DEDG and MC methods because these are viewed as the current state of the art in direct-detection lidar. Successful ground-based demonstrations of direct-detection wind measurements have resulted in proposals for spaceborne systems. With this new emphasis on spaceborne systems comes the need for accurate prediction of spaceborne direct-detection Doppler lidar performance. Previously, the EDG and MC methods have been compared although only for aerosol Doppler systems. A recent paper by McGill and Spinhirne compares the DEDG and MC methods in a non-system specific manner for both the aerosol and molecular Doppler systems. The purpose of this presentation is to extend the previous work of McGill and Spinhirne to examine the performance of spaceborne profiling systems. Particular emphasis will be placed on the molecular systems, as these are viewed as the strength of direct-detection Doppler lidar.

McGill, Matthew J.↗
NASA NTRS1997

A Career in the Solar Wind

This is a personal history of the author's experiences, starting with the earliest direct measurements of the solar wind and continuing through later experiments to investigate the physics of the solar wind and its interaction with comets.

Space Physics↗
DOE OSTI2025

Baltimore Social-Environmental Collaborative (BSEC) Doppler Lidar & Derived Products

This repository contains all processed Doppler‐lidar outputs from the PSU lidar deployed for the Baltimore Social‐Environmental Collaborative (BSEC) project. Vertical Stare Scans (fixed‐beam, vertical profiling): 1 Hz backscatter intensity (m⁻¹ sr⁻¹), signal‐to‐noise ratio (unitless), and Doppler vertical‐velocity (m s⁻¹) on ~30 m range gates, stored as CF-compliant NetCDF. Wind Profiles (horizontal‐wind retrieval): daily NetCDF outputs of retrieved horizontal wind speed (m s⁻¹) and direction (degrees), computed from the angled‐scan returns. Profile Statistics (summary statistics on the vertical velocity): 15 min windows (default) of mean, variance, skewness, kurtosis, high-frequency variance, etc., as a function of height; saved as CF-compliant NetCDF files. Boundary Layer Height (BLH) (fuzzy-logic output): 15 min BLH estimates (m), with lower/upper fuzzy bounds (m) and a quality flag (0–4) indicating data status (e.g., no data, good, below range, ran out of signal, cloud-topped). Cloud Base Height (Haar-gradient detection): 15 min estimates of cloud-base height (m) with a cloud-detection quality flag (0–3: none, low, moderate, high). All five product streams are organized by year and date under their own top-level folders (01_Vertical_Stare_Scans/ through 05_Cloud_Height/). Each folder contains a data_ /YYYY/ subdirectory with daily CF-compliant NetCDF outputs (96 windows per day at 15 min intervals). Global attributes in each file include creation history, version (2.0.0), institution, and source. Instrument & MeasurementsThe PSU Doppler Lidar samples aerosol backscatter (m⁻¹ sr⁻¹), signal-to-noise ratio, and radial velocity at ~1 Hz. Vertical stare scans point the beam straight up; after collecting angled scans through multiple elevation angles, the "Wind Profiles" product contains the fully retrieved horizontal wind speed and direction. Data were collected continuously at ~30 m range resolution, with a typical height ceiling of ~12 km. How to Use Open any NetCDF with Python's xarray, MATLAB, or similar CF-compliant tools. Stare scans and angled-scan retrievals (Wind Profiles) are CF-compliant daily NetCDF files. Profile-Statistics, BLH, and Cloud Height files are daily 15 min summaries (96 time steps per file). Inspect the included variables (e.g., vertical_velocity_variance, wind_speed, BLH, cloud_base_height) for your analyses. Use the quality flags (BLH_flag, cloud_flag) to filter out poor-quality retrievals. For more information or questions about processing methods, please contact:Nicholas E. Prince ⟨nec5299@psu.edu⟩Penn State Department of Meteorology & Atmospheric Science

Air Quality↗