SEARCH · Engineering Papers

Results for “LiS”

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.

SourceResearch connectionFrom yearThrough year

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

At least 37 records · Page 2

All sources NASA NTRS DOE OSTI

NASA NTRS2007

An Integrated High Resolution Hydrometeorological Modeling Testbed using LIS and WRF

Scientists have made great strides in modeling physical processes that represent various weather and climate phenomena. Many modeling systems that represent the major earth system components (the atmosphere, land surface, and ocean) have been developed over the years. However, developing advanced Earth system applications that integrates these independently developed modeling systems have remained a daunting task due to limitations in computer hardware and software. Recently, efforts such as the Earth System Modeling Ramework (ESMF) and Assistance for Land Modeling Activities (ALMA) have focused on developing standards, guidelines, and computational support for coupling earth system model components. In this article, the development of a coupled land-atmosphere hydrometeorological modeling system that adopts these community interoperability standards, is described. The land component is represented by the Land Information System (LIS), developed by scientists at the NASA Goddard Space Flight Center. The Weather Research and Forecasting (WRF) model, a mesoscale numerical weather prediction system, is used as the atmospheric component. LIS includes several community land surface models that can be executed at spatial scales as fine as 1km. The data management capabilities in LIS enable the direct use of high resolution satellite and observation data for modeling. Similarly, WRF includes several parameterizations and schemes for modeling radiation, microphysics, PBL and other processes. Thus the integrated LIS-WRF system facilitates several multi-model studies of land-atmosphere coupling that can be used to advance earth system studies.

Kumar, Sujay V.↗

NASA NTRS2019

Evaluation Analysis of NASA SMAP L3 and L4 and SPoRT-LIS Soil Moisture Data in the United States

Soil moisture has a critical role in the development, frequency and persistence of climatic and hydrologic extremes such as drought, heat wave and flooding events. In situ soil moisture data are uneven and sparse in time and space. This highlights the need to utilize other soil moisture sources to fill this spatiotemporal gap. The goal of this study is to validate one satellite-based and two model-based soil moisture datasets with in situ data across the United States. Soil moisture information from the Soil Moisture Active Passive (SMAP) enhanced level 3 (L3) (SMAP L3) and modeled level 4 (L4) (SMAP L4) data at 9-km resolution and Short-term Prediction Research and Transition-Land Information System (SPoRT-LIS) modeled at 3-km resolution were selected for evaluation. SPoRT-LIS is a near real-time, high resolution operational land analysis data. Ground-based data were obtained from the North American Soil Moisture Database (NASMD) for 362 stations. Seven statistical indicators including anomaly, Spearman, and Pearson correlation coefficients, the systematic error (Bias), root mean square error (RMSE), unbiased root mean square error (ubRMSE), and normalized standard deviation (SDV) were used to evaluate the satellite- and model-derived soil moisture data. In addition, the triple collocation (TC) error model was used to measure the error among SMAP L4, SPoRT-LIS and ground-based data. This study assesses which satellite or modeled dataset is most appropriate for specific times and locations to use as a surrogate for in situ observations. Temporal and spatial analysis demonstrated that, overall, SMAP L4 performed better than SMAP L3 and SPoRT-LIS. Strong agreement was observed between SMAP L4 and in situ observations (ρ = 0.53, Bias = −0.006) in all seasons and most regions with various land covers, especially in winter and in the central regions of the United States. For croplands, SMAP L4 presented the best agreement with in situ data, analyzing all period (ρ = 0.60) and non-winter period (ρ = 0.61) separately.

Tavakol, Ameneh↗

NASA NTRS1999

Comparison of Ground-Based 3-Dimensional Lightning Mapping Observation with Satellite-Based LIS Observations in Oklahoma

3-dimensional lightning mapping observations were obtained in central Oklahoma during June 1998, using New Mexico Tech's Lightning Mapping Array (LMA). The results have been compared with observations of the discharges from space obtained by NASA's Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) spacecraft. Excellent spatial and temporal correlations were obtained between the two sets of observations. All discharges seen by LIS were mapped by the LMA. Most of the detected optical events were associated with lightning channels that extended into the upper part of the storm. Cloud-to-ground discharges that were confined to mid- and lower-altitudes tended to be detected by LIS at the time of late-stage return strokes. Extensive illumination tended to occur in impulsive bursts toward the end or part way through intracloud discharges and appeared to be produced by energetic K-changes that typically occur at these times.

Thomas, Ronald J.↗

NASA NTRSDate not supplied

The International Space Station Lightning Imaging Sensor (ISS LIS): An Overview of More Than Five Years of Science and Operations, With a Look Toward the Future of Spaceborne Lightning Observations

- ISS LIS is the flight spare of the original Tropical Rainfall Measuring Mission (TRMM) LIS, which was kept in storage since the 1990s. - Modified and then integrated as a hosted payload on DoD Space Test Program-Houston 5 (STP-H5). Launched on SpaceX CRS-10 on February 19, 2017. - LIS measures global lightning (amount, rate, radiant energy) during day and night, with storm-scale resolution, millisecond timing, and high, spatially uniform detection efficiency.

Lightning↗

NASA NTRS2009

Climate and Lightning: An updated TRMM-LIS Analysis

The TRMM Lightning Imaging Sensor (LIS) has sampled global tropical and sub-tropical lightning flash densities for approximately 11 years. These data were originally processed and results presented by the authors in the 3rd AMS MALD Conference held in 2007 using both pre and post TRMM-boost lightning data. These data were normalized for the orbit boost by scaling the pre-boost data by a fixed constant based on the different swath areas for the pre and post-boost years (post-boost after 2001). Inevitably, one must question this simple approach to accounting for the orbit boost when sampling such a noisy quantity. Hence we are in the process of reprocessing the entire 11-year TRMM LIS dataset to reduce the orbit swath of the post-boost era to that of the pre-boost in order to eliminate sampling bias in the dataset. Study of the diurnal/seasonal/annual sampling suggests that those biases are already minimal and should not contribute to error in examination of annual trends. We will present new analysis of the 11-year annual trends in total lightning flash density for all latitudinal belts and select regions/regimes of the tropics as related to conventional climate signals and precipitation contents in the same period. The results should enable us to address, in some fashion, the sensitivity of the lightning flash density to subtle changes in climate.

Petersen, Walter A.↗

NASA NTRS2010

Analysis of TRMM-LIS Lightning and Related Microphysics Using a Cell-Scale Database

Previous studies of tropical lightning activity using Tropical Rainfall Measurement Mission (TRMM) Lightning Imaging Sensor (LIS) data performed analyses of lightning behavior over mesoscale "feature" scales or over uniform grids. In order to study lightning and the governing ice microphysics intrinsic to thunderstorms at a more process-specific scale (i.e., the scale over which electrification processes and lightning occur in a "unit" thunderstorm), a new convective cell-scale database was developed by analyzing and refining the University of Utah's Precipitation Features database and retaining precipitation data parameters computed from the TRMM precipitation radar (PR), microwave imager (TMI) and LIS instruments. The resulting data base was to conduct a limited four-year study of tropical continental convection occurring over the Amazon Basin, Congo, Maritime Continent and the western Pacific Ocean. The analysis reveals expected strong correlations between lightning flash counts per cell and ice proxies, such as ice water path, minimum and average 85GHz brightness temperatures, and 18dBz echo top heights above the freezing level in all regimes, as well as regime-specific relationships between lighting flash counts and PR-derived surface rainfall rates. Additionally, radar CFADs were used to partition the 3D structure of cells in each regime at different flash counts. The resulting cell-scale analyses are compared to previous mesoscale feature and gridded studies wherever possible.

Leroy, Anita↗

NASA NTRS2014

Global Patterns of Lightning Properties Derived by OTD and LIS

The satellite instruments Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) provide unique empirical data about the frequency of lightning flashes around the globe (OTD), and the tropics (LIS), which 5 has been used before to compile a well received global climatology of flash rate densities. Here we present a statistical analysis of various additional lightning properties derived from OTD/LIS, i.e. the number of so-called "events" and "groups" per flash, as well as 10 the mean flash duration, footprint and radiance. These normalized quantities, which can be associated with the flash "strength", show consistent spatial patterns; most strikingly, oceanic flashes show higher values than continental flashes for all properties. Over land, regions with high (Eastern US) 15 and low (India) flash strength can be clearly identified. We discuss possible causes and implications of the observed regional differences. Although a direct quantitative interpretation of the investigated flash properties is difficult, the observed spatial patterns provide valuable information for the 20 interpretation and application of climatological flash rates. Due to the systematic regional variations of physical flash characteristics, viewing conditions, and/or measurement sensitivities, parametrisations of lightning NOx based on total flash rate densities alone are probably affected by regional biases.

Beirle, Steffen↗

DOE OSTI2020

Materials Data on LiS by Materials Project

LiS is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Li1+ is bonded to six equivalent S1- atoms to form a mixture of edge and corner-sharing LiS6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Li–S bond lengths are 2.51 Å. S1- is bonded to six equivalent Li1+ atoms to form a mixture of edge and corner-sharing SLi6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on LiS by Materials Project

LiS crystallizes in the tetragonal I-4m2 space group. The structure is three-dimensional. Li1+ is bonded in a 4-coordinate geometry to four equivalent S1- atoms. All Li–S bond lengths are 2.40 Å. S1- is bonded in a 4-coordinate geometry to four equivalent Li1+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on LiS by Materials Project

LiS crystallizes in the tetragonal I-42m space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four equivalent S1- atoms to form distorted corner-sharing LiS4 tetrahedra. There are two shorter (2.42 Å) and two longer (2.72 Å) Li–S bond lengths. In the second Li1+ site, Li1+ is bonded to four equivalent S1- atoms to form distorted corner-sharing LiS4 trigonal pyramids. All Li–S bond lengths are 2.47 Å. S1- is bonded in a 4-coordinate geometry to four Li1+ and one S1- atom. The S–S bond length is 2.13 Å.

36 MATERIALS SCIENCE↗

NASA NTRS1991

Data simulation for the Lightning Imaging Sensor (LIS)

This project aims to build a data analysis system that will utilize existing video tape scenes of lightning as viewed from space. The resultant data will be used for the design and development of the Lightning Imaging Sensor (LIS) software and algorithm analysis. The desire for statistically significant metrics implies that a large data set needs to be analyzed. Before 1990 the quality and quantity of video was insufficient to build a usable data set. At this point in time, there is usable data from missions STS-34, STS-32, STS-31, STS-41, STS-37, and STS-39. During the summer of 1990, a manual analysis system was developed to demonstrate that the video analysis is feasible and to identify techniques to deduce information that was not directly available. Because the closed circuit television system used on the space shuttle was intended for documentary TV, the current value of the camera focal length and pointing orientation, which are needed for photoanalysis, are not included in the system data. A large effort was needed to discover ancillary data sources as well as develop indirect methods to estimate the necessary parameters. Any data system coping with full motion video faces an enormous bottleneck produced by the large data production rate and the need to move and store the digitized images. The manual system bypassed the video digitizing bottleneck by using a genlock to superimpose pixel coordinates on full motion video. Because the data set had to be obtained point by point by a human operating a computer mouse, the data output rate was small. The loan and subsequent acquisition of a Abekas digital frame store with a real time digitizer moved the bottleneck from data acquisition to a problem of data transfer and storage. The semi-automated analysis procedure was developed using existing equipment and is described. A fully automated system is described in the hope that the components may come on the market at reasonable prices in the next few years.

Boeck, William L.↗

NASA NTRS1997

ALDF Data Retrieval Algorithms for Validating the Optical Transient Detector (OTD) and the Lightning Imaging Sensor (LIS)

A linear algebraic solution is provided for the problem of retrieving the location and time of occurrence of lightning ground strikes from in Advanced Lightning Direction Finder (ALDF) network. The ALDF network measures field strength, magnetic bearing, and arrival time of lightning radio emissions and solutions for the plane (i.e.. no Earth curvature) are provided that implement all of these measurements. The accuracy of the retrieval method is tested using computer-simulated data sets and the relative influence of bearing and arrival time data on the outcome of the final solution is formally demonstrated. The algorithm is sufficiently accurate to validate NASA's Optical Transient Detector (OTD) and Lightning Imaging System (LIS). We also introduce a quadratic planar solution that is useful when only three arrival time measurements are available. The algebra of the quadratic root results are examined in detail to clarify what portions of the analysis region lead to fundamental ambiguities in source location. Complex root results are shown to be associated with the presence of measurement errors when the lightning source lies near an outer sensor baseline of the ALDF network. For arbitrary noncollinear network geometries and in the absence of measurement errors, it is shown that the two quadratic roots are equivalent (no source location ambiguity) on the outer sensor baselines. The accuracy of the quadratic planar method is tested with computer-generated data sets and the results are generally better than those obtained from the three station linear planar method when bearing errors are about 2 degrees.

Koshak, W. J.↗

NASA NTRS1999

Land-Ocean Differences in LIS and OTD Tropical Lightning Observations

Significant differences are known to exist on a global scale between continental and oceanic total lightning regional flash rates, suggesting differences in the properties of convective storms in these regimes. Lightning properties observed by the Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) over land and ocean are compared, limited to analysis over the tropics in order to simplify physical interpretation. We find that the mean flash rates of individual storms over tropical land only exceed those over ocean by a factor of 2 (far less than the observed differences in regional flash rates). However, the average nearest neighbor distance of continental thunderstorms in half that over oceans. Cloud-top lightning optical radiance in oceanic storms is also twice as large as over land, suggesting either more energetic flashes over the oceans or less intervening cloud particles.

Boccippio, Dennis J.↗

NASA NTRS1999

Land-Ocean Differences in LIS and OTD Tropical Lightning Observations

Significant differences are known to exist on a global scale between continental and oceanic total lightning regional flash rates, suggesting differences in the properties of convective storms in these regimes. Lightning properties observed by the Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) over land and ocean are compared, limited to analysis over the tropics in order to simplify physical interpretation. We find that the mean flash rates of individual storms over tropical land only exceed those over ocean by a factor of 2 (far less than the observed differences in regional flash rates). However, the average nearest neighbor distance of continental thunderstorms is half that over oceans. Cloud-top lightning optical radiance in oceanic storms is also twice as large as over land, suggesting either more energetic flashes over the oceans or less intervening cloud particles.

Boccippio, D. J.↗

NASA NTRS2003

Lightning and Precipitation: Observational Analysis of LIS and PR

Lightning flash rate can identify areas of convective rainfall when the storms are dominated by ice-phase precipitation. Modeling and observational studies indicate that cloud electrification and microphysics are very closely related and it is of great interest to understand the relationship between lightning and cloud microphysical quantities. Analyzing data from the Lightning Image Sensor (LIS) and the Precipitation Radar (PR), we show a quantitative relationship between microphysical characteristics of thunderclouds and lightning flash rate. We have performed a complete analysis of all data available over the Mediterranean during the TRMM mission and show a range of reflective profiles as a function of lightning activity for both convective and stratiform regimes as well as seasonal variations. Due to the increasing global coverage of lightning detection networks, this kind of study can used to extend the knowledge about thunderstorms and discriminate between different regimes in regions where radar measurements are readilly available.

Adamo, C.↗

NASA NTRS2007

Diurnal Lightning Distributions as Observed by the Optical Transient Detector (OTD) and the Lightning Imaging Sensor (LIS)

Data obtained from the OTD (April 1995 to March 2000) and LIS (December 1997 to December 2005) satellites (70 and 35 degree inclination low earth orbits, respectively) are used to statistically determine the number of flashes in the diurnal cycle both as a function of local and universal time. Also included are global flash density maps. The data is further subdivided by season, continental versus oceanic, night time versus day time, northern versus southern hemisphere, and other regions of interest such as the Brazilian rain forest and the Congo. The data includes corrections for detection efficiency and instrument view time. The data was compared with the "Carnegie Curve" and the diurnal global thunderstorm contributions from thunderday statistics fiom different continents as derived by Whipple and Scrase, 1936. Initial results indicate that the northern hemisphere fall (September to November) has a larger amplitude than the northern hemisphere spring (March to May). This may be due to the differences in the contribution of the Brazilian rain forest during these periods (the main lightning peak starts in September and ends in February with a secondary peak in April). For some areas of the world, the peak of the diurnal curve appears to be shifted to later in the evening.

Blakeslee, R. J.↗

NASA NTRS2007

Diurnal Lightning Distributions as Observed by the Optical Transient Detector (OTD) and the Lightning Imaging Sensor (LIS)

Data obtained from the OTD (April 1995 to March 2000) and LIS (December 1997 to December 2005) satellites (70 and 35 degree inclination low earth orbits, respectively) are used to statistically determine the number of flashes in the diurnal cycle both as a function of local and universal time. Also included are global flash density maps. The data are further subdivided by season, continental versus oceanic, night time versus day time, northern versus southern hemisphere, and other regions of interest. The data include corrections for detection efficiency and instrument view time. The data are compared with both the "Carnegie Curve" and the diurnal global thunderstorm contributions from thunderday statistics from different continents, and are found to agree closely in phase and amplitude with the global thunderday statistics. The analysis also indicates that the southern hemisphere spring (September to November) has larger amplitude than the southern hemisphere fall (March to May). This may be due to differences in the contribution from the Brazilian rain forest during these periods. In general, as highlighted by a difference analysis, more lightning is observed in local springtime than the fall for continental locations, while oceanic regions display an opposite effect. For some areas of the world, the peak of diurnal curve appears to be shifted to later in the evening.

Bailey, Jeff C.↗

NASA NTRS2007

Lightning Charge Retrievals: Dimensional Reduction, LDAR Constraints, and a First Comparison w/ LIS Satellite Data

A "dimensional reduction" (DR) method is introduced for analyzing lightning field changes whereby the number of unknowns in a discrete two-charge model is reduced from the standard eight to just four. The four unknowns are found by performing a numerical minimization of a chi-squared goodness-of-fit function. At each step of the minimization, an Overdetermined Fixed Matrix (OFM) method is used to immediately retrieve the best "residual source". In this way, all 8 parameters are found, yet a numerical search of only 4 parameters is required. The inversion method is applied to the understanding of lightning charge retrievals. The accuracy of the DR method has been assessed by comparing retrievals with data provided by the Lightning Detection And Ranging (LDAR) instrument. Because lightning effectively deposits charge within thundercloud charge centers and because LDAR traces the geometrical development of the lightning channel with high precision, the LDAR data provides an ideal constraint for finding the best model charge solutions. In particular, LDAR data can be used to help determine both the horizontal and vertical positions of the model charges, thereby eliminating dipole ambiguities. The results of the LDAR-constrained charge retrieval method have been compared to the locations of optical pulses/flash locations detected by the Lightning Imaging Sensor (LIS).

Koshak, William↗