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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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24 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

GOES-R AWG GLM Val Tool Development

We are developing tools needed to enable the validation of the Geostationary Lightning Mapper (GLM). In order to develop and test these tools, we have need of a robust, high-fidelity set of GLM proxy data. Many steps have been taken to ensure that the proxy data are high quality. LIS is the closest analog that exists for GLM, so it has been used extensively in developing the GLM proxy. We have verified the proxy data both statistically and algorithmically. The proxy data are pixel (event) data, called Level 1B. These data were then clustered into flashes by the Lightning Cluster-Filter Algorithm (LCFA), generating proxy Level 2 data. These were then compared with the data used to generate the proxy, and both the proxy data and the LCFA were validated. We have developed tools to allow us to visualize and compare the GLM proxy data with several other sources of lightning and other meteorological data (the so-called shallow-dive tool). The shallow-dive tool shows storm-level data and can ingest many different ground-based lightning detection networks, including: NLDN, LMA, WWLLN, and ENTLN. These are presented in a way such that it can be seen if the GLM is properly detecting the lightning in location and time comparable to the ground-based networks. Currently in development is the deep-dive tool, which will allow us to dive into the GLM data, down to flash, group and event level. This will allow us to assess performance in comparison with other data sources, and tell us if there are detection, timing, or geolocation problems. These tools will be compatible with the GLM Level-2 data format, so they can be used beginning on Day 0.

Bateman, Monte↗
NASA NTRS2012

Flash Detection Efficiencies of Long Range Lightning Detection Networks During GRIP

We flew our Lightning Instrument Package (LIP) on the NASA Global Hawk as a part of the Genesis and Rapid Intensification Processes (GRIP) field program. The GRIP program was a NASA Earth science field experiment during the months of August and September, 2010. During the program, the LIP detected lighting from 48 of the 213 of the storms overflown by the Global Hawk. The time and location of tagged LIP flashes can be used as a "ground truth" dataset for checking the detection efficiency of the various long or extended range ground-based lightning detection systems available during the GRIP program. The systems analyzed included Vaisala Long Range (LR), Vaisala GLD360, the World Wide Lightning Location Network (WWLLN), and the Earth Networks Total Lightning Network (ENTLN). The long term goal of our research is to help understand the advantages and limitations of these systems so that we can utilize them for both proxy data applications and cross sensor validation of the GOES-R Geostationary Lightning Mapper (GLM) sensor when it is launched in the 2015 timeframe.

Mach, Douglas M.↗
NASA NTRS2017

Terrestrial Gamma Ray Flashes due to Particle Acceleration in Tropical Storm Systems

Terrestrial gamma ray flashes (TGFs) are submillisecond flashes of energetic radiation that are believed to emanate from intracloud lightning inside thunderstorms. This emission can be detected hundreds of kilometers from the source by space-based observatories such as the Fermi Gamma-ray Space Telescope (Fermi). The location of the TGF-producing storms can be determined using very low frequency (VLF) radio measurements made simultaneously with the Fermi detection, allowing additional insight into the mechanisms which produce these phenomena. In this paper, we report 37 TGFs originating from tropical storm systems for the first time. Previous studies to gain insight into how tropical cyclones formed and how destructive they can be include the investigation of lightning flash rates and their dependence on storm evolution. We find TGFs to emanate from a broad range of distances from the storm centers. In hurricanes and severe tropical cyclones, the TGFs are observed to occur predominately from the outer rainbands. A majority of our sample also show TGFs occurring during the strengthening phase of the encompassing storm system. These results verify that TGF production closely follows when and where lightning predominately occurs in cyclones. The intrinsic characteristics of these TGFs were not found to differ from other TGFs reported in larger samples. We also find that some TGF-producing storm cells in tropical storm systems far removed from land have a low number of WWLLN sferics. Although not unique to tropical cyclones, this TGF/sferic ratio may imply a high efficiency for the lightning in these storms to generate TGFs.

Roberts, O. S.↗
DOE OSTI2020

Analysis of Electric and Magnetic Lightning-Generated Wave Amplitudes Measured by the Van Allen Probes

Herein we provide a statistical analysis of both electric and magnetic field wave amplitudes of very low frequency lightning-generated waves (LGWs) based on the equivalent of 11.5 years of observations made by the Van Allen Probes encompassing ~24.6 × 10 6 survey mode measurements. We complement this analysis with data from the ground-based World Wide Lightning Location Network to explore differences between satellite and ground-based measurements. LGW mean amplitudes are found to be low compared with other whistler mode waves (1 ± 1.6 pT and 19 ± 59 μV/m). Extreme events (1/5,000) can reach 100 pT and contributes strongly to the mean power below $L$ = 2. We find excellent correlations between World Wide Lightning Location Network-based power and wave amplitudes in space at various longitudes. We reveal strong dayside ionospheric damping of the LGW electric field. LGW amplitudes drop for $L$ < 2, contrary to the Earth's intense equatorial lightning activity. We conclude that it is difficult for equatorial LGW to propagate and remain at $L$ < 2.

Electric wave power↗
DOE OSTI2021

CAPE Threshold for Lightning Over the Tropical Ocean

Here, we investigate the relationship between convective available potential energy (CAPE), precipitation, the number and size of storms and overshooting tops, and lightning stroke density ($\mathcal{f}$) over the Central America region. While $\mathcal{f}$ increases almost linearly with CAPE 1/2 over land, $\mathcal{f}$ is nearly muted over the ocean when CAPE is small. In the high-CAPE regime, on the contrary, oceanic storms produce as many lightning flashes as land storms. We show that individual oceanic storms are smaller and contain fewer overshooting tops compared to land storms, although the difference exists across low- and high-CAPE regimes. While $\mathcal{f}$ increases as individual storm size increases, the storm size required to produce lightning appears to be disproportionately high in the low-CAPE regime, likely due to the stronger entrainment effect. The entrainment effect on $\mathcal{f}$ in the low-CAPE regime appears to be much weaker over land. Applying the CAPE threshold for lightning over the ocean to the CAPE-based lightning parameterization scheme of Romps et al. (2014), https://doi.org/10.1126/science.1259100 improves its performance, in particular, at representing the land-sea contrast in $\mathcal{f}$.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Interactions Between Lightning and Ship Traffic

It is important to understand connections between society and the natural environment for anticipating hazards and anthropogenic effects on the Earth system. In this study, we conduct a detailed exploration of interactions between oceanic thunderstorms and maritime traffic. Shipping traffic produces aerosols that perturb the otherwise “clean” ocean environment. Prior work proposed these aerosol effects as the cause of increased lightning over certain shipping lanes. However, introducing tall grounded objects into a high electric field environment might also facilitate lightning discharges, as we see with upward lightning over land. We consider both possibilities. Our analyses of the thunderstorms responsible for enhanced lightning activity over the shipping lane with the clearest anthropogenic signal indicate that the enhancement results from an increased frequency of lightning-producing storms. Observed variations in thunderstorm microphysics between the shipping lane and nearby oceans are small compared to natural factors such as the Indian monsoon, and are on the same scale as the local variability in the data. By contrast, matching lightning stroke data with ship transponder events in oceanic regions where public data are available reveals a strong signal from direct ship interactions. Lightning is 15× (66×) more likely to occur at a ship location compared to 2 km (25 km) away. These results highlight the central role of direct ship interactions in explaining lightning enhancements over shipping lanes. We also document the frequency of these direct lightning interactions across various categories of vessels and on individual ships present in the public data.

54 ENVIRONMENTAL SCIENCES↗