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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Graupel and Hail Identification Algorithm for the Dual-frequency Precipitation Radar (DPR) on the GPM Core Satellite

Precipitation consists of many types of hydrometeors, such as raindrops, ice crystals, graupel, and hail. Due to their impacts, graupel and hail (GH) have received particular attention in the literature. Global Precipitation Measurement (GPM) dual-frequency radar (DPR) has proved to be a very reliable system for global precipitation retrievals. This paper aims to develop a GH identification algorithm for GPM DPR. This algorithm is constructed using a precipitation type index (PTI) defined for DPR. The PTI is effective in separating hydrometeor types and is calculated using measurements of reflectivity, dual-frequency ratio, and storm top height data. The output of the algorithm is a Boolean product representing the existence of graupel or hail along with the vertical profile for each Ku- and Ka-band matched footprint. Cross validation is performed with the Weather Service Radar (WSR-88D) network over continental United States as well as during the Remote sensing of Electrification, Lightning, and Mesoscale/Microscale Processes with Adaptive Ground Observations (RELAMPAGO) experiment. Evaluation of the GH identification algorithm is performed on a global basis, which illustrates promising comparisons with the global lightning and hail precipitation maps generated using radar and radiometer.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1990

Lightning observations from space shuttle

The experimental program of the Earth Sciences and Applications Division at NASA/MSFC includes development of the Lightning Imaging Sensor (LIS) for the NOAA Earth Observing System (EOS) Polar Platform. The research plan is to use existing lightning information to generate simulated data for the LIS experiment. Navigation algorithms were used to transform pixel locations to latitude and longitude values. The simulated data would then be used to test and develop algorithms for the analysis of LIS data. Individual frames of video imagery obtained from Space Shuttle Missions provide the raw data for the simulation. Individual video frames were digitized to get the pixel locations of lightning flashes. The pixel locations will be used to locate the geographical position of the event. Because of a lack of detailed knowledge of camera orientation with respect to the Space Shuttle, video scenes that contain identifiable city lights were chosen for analysis. A method for locating the payload bay camera axis was developed and tested. Two measurements are needed: the pixel location of the apparent horizon and a timed siting of a known location passing the principal line of the image. Individual video frames were navigated and lightning illuminated clouds were located on the map. Satisfactory agreement in location was achieved for cities and LLP lightning locations. Ground truth measurements were compared to satellite observations. A vertical lightning event was identified on the horizon. Very low frequency (VLF) transmission on this particular occassion shows a strong response to negative cloud to cloud flashes.

Boeck, William L.↗
NASA NTRS1984

Lightning activity and severe storm structure

Space-time mapping of VHF sources from four severe storms on June 19, 1980 reveals that lightning processes for cloud-to-ground (CG) and large intracloud (IC) flashes are confined to an altitude below about 10 km and closely associated with the central regions of high reflectivity. Another class of IC flashes produces a splattering of sources within the storms' main electrically active volumes and also within the large divergent wind canopy aloft. There is no apparent temporal association between the small high altitude IC flashes that occur almost continuously and the large IC and CG flashes that occur sporadically in the lower portions of storms.

Taylor, W. L.↗
DOE OSTI2021

Combined Optical and Radio-Frequency Measurements of a Lightning Megaflash by the FORTE Satellite

The optical and VHF instrumentation on the Fast On-Orbit Recording of Transient Events (FORTE) satellite is used to document the combined phenomenology evolution of a lightning “megaflash” – mesoscale lightning that propagates laterally over exceptional distances. We identify a FORTE flash whose maximum extent was 82 km and inferred length over multiple distinct branches exceeded 100 km. This flash lasted 1.2 s and produced 250 optical and 591 RF events. We find that the channel development mapped by FORTE’s pixelated lightning imager (LLS) occurred at a typical speed of 2.6x10 5 m s -1 and was accompanied by sustained periods of VHF emission that could individually exceed 100 ms in duration. The impulsive IC events generated by the flash indicate that this development occurred at altitudes between 3 and 8 km. Four +CG strokes were identified in the VHF waveform data that are responsible for two of the three highly-radiant LLS groups (two of the +CGs were not as optically bright as the others). These strokes occurred at different locations throughout the flash footprint with the most distant strokes separated by approximately 50 km. These space-based observations match previous observations of megaflashes as well as ground-based measurements of negative leader development during “spider” lightning, suggesting that FORTE is sensing the same phenomena.

Peterson, Michael Jay↗
NASA NTRS1991

A system for mapping sources of VHF and electric field pulses from in-cloud lightning at KSC

The literature concerning VHF radiation and wideband electric fields from in-cloud lightning is reviewed. VHF location systems give impressive radio images of lightning in clouds with high spatial and temporal resolution. Using systems based on long and short baseline time-or-arrival and interferometry, workers have detected VHF sources that move at speeds of 10(exp 5) to 10(exp 8) m/s. The more slowly moving sources appear to be associated with channel formation but the physical basis for the higher speeds is not clear. In contrast, wideband electric fields are directly related to physical parameters such as current and tortuosity. A long baseline system is described to measure simultaneously VHF radiation and wideband electric fields at five stations at Kennedy Space Center. All signals are detected over remote, isolated ground planes with fiber optics for data transmission. The modification of this system to map rapidly varying dE/dt pulses is discussed.

Thomson, Ewen M.↗
DOE OSTI2023

Insights Into Lightning K‐Leader Initiation and Development From Three Dimensional Broadband Interferometric Observations

Abstract We report detailed observations of K‐leaders and the activity between them with the three‐dimensional Broadband Interferometric Mapping and Polarization system (BIMAP‐3D) at Los Alamos National Laboratory. It is found that K‐leaders have a general propagation trend of initial acceleration and then gradual deceleration, and the corresponding very high frequency (VHF) radiation power is exponentially correlated with the leader speed. Based on the 3D development and simultaneous electric field change measurement, some simple K‐leaders can be modeled with time‐evolving point charges at the propagating leader tip and at the stationary origin. We found that the charge magnitude increases during the initial acceleration stage and stays relatively constant for the rest of the development. K‐leaders are observed to interact with other branches; the branches affect the leader's propagation speed, and may affect the charge transfer. After the occurrence of a K‐leader, VHF emissions are quenched for several milliseconds. VHF sources then reappear in an impulsive and scattered manner as “twinkling,” and these sources are found not uniquely on the so‐called needles, but also on the main channel. These twinkling sources start near the apparent positive leader tip, and extend back toward the direction of the flash origin at about 10 5 m/s, while the apparent positive tip continues to extend forward at about 10 4 m/s. The twinkling extending toward the direction of flash origin appears to initiate the following K‐leader, although it may be interrupted by a K‐leader along a different branch, or simply die out without more K‐leader activity.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Estimating the Electric Fields Driving Lightning Dart Leader Development With BIMAP‐3D Observations

Abstract In this paper, a numerical dart leader model has been implemented to understand the leader's development and the corresponding electric field changes observed by the 3D broadband mapping and polarization (BIMAP‐3D) system. The model assumes the extending leader channel is equipotential and has a linear charge distribution induced by an ambient electric field. The charge distribution induced by the ambient field can be used to model the electric field change at the ground. We then find the ambient electric field which best fits the field change measurements at the two BIMAP stations. The estimated ambient electric field decreases in the direction of dart leader propagation. Our observations and modeling results are consistent with our earlier hypothesis that dart leader speed is proportional to the electric field at the leader tip. The model also supports our earlier analysis that leader speed variations near branch junctions were due to previous charge deposits near the junctions. The modeled tip electric field is generally lower than the breakdown field unless the pre‐dart‐leader channel has a significant temperature of 3,000 K. This is consistent with the fact that dart leaders typically do not form new branches into the virgin air. Furthermore, the tip field is generally close to the negative streamer stability field at ambient temperatures, explaining the nature of the narrow and well‐defined channel structure. In addition to the charge distribution and the ambient and tip electric field, the development of the channel potential and current distribution are also presented.

3D lightning mapping↗
NASA NTRS1978

Doppler radar observation of thunderstorm circulation in the 1977 trip program

Storm data obtained on August 1, 1977 are examined in an attempt to interpret the relationship between lightning occurrence and the thunderstorm inner dynamics and precipitation processes. Horizontal maps are presented which indicated the position of radiation sources detected by the Lightning Detection and Ranging (LDAR) network, together with the horizontal motion fields and radar reflectivity data. Detailed inspection of these fields showed that, although radiation sources are found in the vicinity of precipitation cells, they are not located in the heavy precipitation areas, but rather on their rear side in regions where the configuration of the wind fields suggests the presence of updrafts.

Lhermitte, R. M.↗
NASA NTRS1986

Plotting Lightning-Stroke Data

Data on lightning-stroke locations become easier to correlate with cloudcover maps with aid of new graphical treatment. Geographic region divided by grid into array of cells. Number of lightning strokes in each cell tabulated, and value representing density of lightning strokes assigned to each cell. With contour-plotting routine, computer draws contours of lightning-stroke density for region. Shapes of contours compared directly with shapes of storm cells.

Tatom, F. B.↗
NASA NTRS1982

Maxwell currents under thunderstorms

Time variations observed in thunderstorm electric fields may be interpreted in terms of a total Maxwell current density, varying slowly with time in the intervals between lightning discharges, which can be used to estimate and map thunderstorms. Using the quasi-static behavior of the Maxwell current density, an expression is derived for the field-dependent current density under a thunderstorm during the field recovery following a lightning discharge. Values of air conductivity under the small storm which range from 2 to 6 x 10 to the -13th mho/m are inferred. Data are presented which indicate that the area-average Maxwell current is not usually affected by lightning, and instead varies slowly throughout the evolution of the storm. In light of this, it is suggested that cloud electrification processes probably do not depend on the cloud electric field as much as on the more slowly varying storm dynamics and meteorological structure.

Krider, E. P.↗
NASA NTRS1997

Nitrogen Oxides and Ozone from B-747 Measurements (NOXAR) During POLINAT-2 and SONEX: Overview and Case Studies on Continental and Marine Convection

In the framework of the project POLINAT 2 (Pollution in the North Atlantic Flight Corridor) we measured NO(x) (NO and NO2) and ozone on 85 flights through the North Atlantic Flight Corridor (NAFC) with a fully automated system permanently installed aboard an in-service Swissair B-747 airliner in the period of August to November 1997. The averaged NO(x) concentrations both in the NAFC and at the U.S. east coast were similar to that measured in autumn 1995 with the same system. The patchy occurrence of NO(x) enhancements up to 3000 pptv over several hundred kilometers (plumes), predominately found over the U.S. east coast lead to a log-normal NO(x) probability density function. In three case studies we examine the origins of such plumes by combining back-trajectories with brightness temperature enhanced (IR) satellite imagery, lightning observations from the U.S. National Lightning Detection Network (NLDN) and the Optical Transient Detector (OTD) satellite. We demonstrate that the location of NO(x) plumes can be well explained with maps of convective influence. We show that the number of lightning flashes in cluster of marine thunderstorms is proportional to the NO(x) concentrations observed several hundred kilometers downwind of the anvil outflows. From the fact that in autumn the NO(x) maximum was found several hundred kilometers off the U.S. east coast, it can be inferred that thunderstorms triggered over the warm Gulf Stream current are major sources for the regional upper tropospheric NO(x) budget in autumn.

Jeker, Dominique P.↗
NASA NTRS1985

Optical characteristics of lightning and thunderstorm currents

Researchers determined that lightning can be used to determine the diurnal variations of thunderstorms, i.e., storms that produce audible thunder, and that these variations are also in good agreement with diurnal variations in rainfall and convective activity. Measurements of the Maxwell current density, J sub m, under active thunderstorms show that this physical quantity is quasi-steady between lightning discharges and that lightning does not produce large changes in J sub m. Maps of J sub m show contours of iso-current density that are consistent with the locations of radar echos and the locations of where lightning has altered the cloud charge distribution.

Krider, E. P.↗
DOE OSTI2020

Data for “Lightning Interferometry Uncertainty, “Focused Interferometry”, and Evidence of Lightning being Ignited by a Cosmic-ray Shower” by Shao et al.

This summarizes the data from our broadband RF interferometric mapping and polarization (BIMAP) system used to produce the figures in the revised manuscript “Lightning Interferometry Uncertainty, “Focused Interferometry”, and Evidence of Lightning being Ignited by a Cosmic-ray Shower” that was originally submitted to Journal of Geophysical Research (JGR) for publication. Note that the original manuscript was titled ““Focused Interferometry” and Fine Structure of Lightning-Initiating Fast Positive Streamers” and was released with LA-UR-19-32549. In accordance with JGR’s data policy (https://www.agu.org/Publish-withAGU/Publish/Author-Resources/Policies/Data-policy), it is the intention to make this data publicly available at the time of article submission. The data set includes raw BIMAP RF data and processed results for two lightning flashes. The data is available in two files (“FPS_data_20170606_361.sav” and “Small_IC_20180520_205644_408.sav”) located at “/home/xshao/HEPL/Analysis” which were packaged with IDL save commend. The raw data includes 3 channels of RF data, 2 channels of RF polarization data, and 1 channel of electric field change data. The processed data includes the RF source positions, source position uncertainties, and the polarization analysis.

58 GEOSCIENCES↗
NASA NTRS1988

Planetographic clustering of low-altitude impulsive electric signals in the night ionosphere of Venus

This paper presents maps of the locations of electromagnetic signals, presumably caused by lightning, which were observed at 730 Hz during the first three nighttime observing seasons of Pioneer Venus Orbiter when the spacecraft reached altitudes low enough to detect the signals. The maps show that there are specific 'active regions' of enhanced signal occurrence, and that at least some of these active regions appear to remain fixed in planetographic coordinates from year to year.

Russel, C. T.↗
NASA NTRS2005

Severe Weather Forecast Decision Aid

This report presents a 15-year climatological study of severe weather events and related severe weather atmospheric parameters. Data sources included local forecast rules, archived sounding data, Cloud-to-Ground Lightning Surveillance System (CGLSS) data, surface and upper air maps, and two severe weather event databases covering east-central Florida. The local forecast rules were used to set threat assessment thresholds for stability parameters that were derived from the sounding data. The severe weather events databases were used to identify days with reported severe weather and the CGLSS data was used to differentiate between lightning and non-lightning days. These data sets provided the foundation for analyzing the stability parameters and synoptic patterns that were used to develop an objective tool to aid in forecasting severe weather events. The period of record for the analysis was May - September, 1989 - 2003. The results indicate that there are certain synoptic patterns more prevalent on days with severe weather and some of the stability parameters are better predictors of severe weather days based on locally tuned threat values. The results also revealed the stability parameters that did not display any skill related to severe weather days. An interactive web-based Severe Weather Decision Aid was developed to assist the duty forecaster by providing a level of objective guidance based on the analysis of the stability parameters, CGLSS data, and synoptic-scale dynamics. The tool will be tested and evaluated during the 2005 warm season.

Bauman, William H., III↗
NASA NTRS1984

Pioneer to Venus - The multiprobe and orbiter missions

The missions of the Pioneer multiprobe and orbiter spacecraft to Venus are surveyed and illustrated with drawings, photographs, maps, and diagrams. The general characteristics of Venus and the pre-Pioneer missions are reviewed; the developmental history of the Pioneer project is traced; the spacecraft and their orbits and deployment are described; and the scientific findings on the planet surface, atmosphere, and ionosphere are summarized. The experiments planned for the extended mission of the orbiter (through reentry in 1992) are briefly characterized, includidng solar-wind-interaction studies, comet detection, ionosphere and aeronomy investigations, global lightning survey, optical observations, gamma-ray-burst detection, radar mapping, gravity measurements, and observations of Halley's Comet during February, 1986.

Craig, R. A.↗
NASA NTRS1999

Nitrogen Oxides and Ozones from B-747 Measurements (NOXAR) during POLINAT 2 and SONEX: Overview and Case-Studies on Continental and Marine Convection

In the framework of the project POLINAT 2 (Pollution in the North Atlantic Flight Corridor) we measured NO(x) (NO and NO2) and ozone on 98 flights through the North Atlantic Flight Corridor (NAFC) with a fully automated system permanently installed aboard an in-service Swissair B-747 airliner in the period of August to November 1997. The averaged NO, concentrations both in the NAFC and at the U.S. east coast were similar to that measured in autumn 1995 with the same system. The patchy occurrence of NO(x), enhancements up to 3000 pptv over several hundred kilometers (plumes), predominately found over the U.S. east coast lead to a log-normal NO(x) probability density function. In three case-studies we examine the origins of such plumes by combining back-trajectories with brightness temperature enhanced (IR) satellite imagery, with lightning observations from the U.S. National Lightning Detection Network (NLDN) or with the Optical Transient Detector (OTD) satellite. For frontal activity above the continental U.S., we demonstrate that the location of NO(x) plumes can be well explained with maps of convective influence. For another case we show that the number of lightning flashes in a cluster of marine thunderstorms is proportional to the NO(x) concentrations observed several hundred kilometers downwind of the anvil outflows and suggest that lightning was the dominant source. From the fact that in autumn the NO, maximum was found several hundred kilometers off the U.S. east coast, it can be inferred that thunderstorms triggered over the warm Gulf Stream current are an important source for the regional upper tropospheric NO(x) budget in autumn.

Jeker, Dominique↗
NASA NTRS1999

An Optimal Relation of Radar Reflectivity to Lightning Rate

Thunderstorms separate charge. Most places they lift positive charge or lower negative, a few places they lift negative or lower positive. The electrical generator is stronger in some parts of the cloud than in others. Our long term goal is to map this generator. Cloud physicists tell us that uncharged ice and water particles become charged by collision, and that the charge transferred depends on size, temperature and humidity. There is still some disagreement about exactly how the charge transferred depends on size, temperature, and humidity. In principle, if we knew this ice physics, and also knew the distribution of particles everywhere in the storm, and the winds everywhere and the temperature and humidity everywhere, then we could compute everywhere the electrical power of the thunderstorm generator. In practice it is difficult to know all these things, particularly the distribution of particles, so it is difficult to use real thunderstorms to falsify cloud electrification theories. We here take one small step towards computing that map of electrical generator power, by relating radar reflectivity profiles of 2000 storms to lightning flash rates of those storms. This small step by itself doesn't falsify any existing electrification theories; it merely places weak constraints on the relation of electric generator power to cloud ice.

Heckman, S.↗