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1. The RELAMPAGO Lightning Mapping Array: Overview and Initial Comparison with the Geostationary Lightning Mapper

   https://doi.org/10.1175/JTECH-D-20-0005.1  

   Lang, Timothy J.; Ávila, Eldo E.; Blakeslee, Richard J.; Burchfield, Jeff; Wingo, Matthew; Bitzer, Phillip M.; Carey, Lawrence D.; Deierling, Wiebke; Goodman, Steven J.; Medina, Bruno Lisboa; et al (August 2020, Journal of Atmospheric and Oceanic Technology)

   Abstract During November 2018–April 2019, an 11-station very high frequency (VHF) Lightning Mapping Array (LMA) was deployed to Córdoba Province, Argentina. The purpose of the LMA was validation of the Geostationary Lightning Mapper (GLM), but the deployment was coordinated with two field campaigns. The LMA observed 2.9 million flashes (≥ five sources) during 163 days, and level-1 (VHF locations), level-2 (flashes classified), and level-3 (gridded products) datasets have been made public. The network’s performance allows scientifically useful analysis within 100 km when at least seven stations were active. Careful analysis beyond 100 km is also possible. The LMA dataset includes many examples of intense storms with extremely high flash rates (>1 s−1), electrical discharges in overshooting tops (OTs), as well as anomalously charged thunderstorms with low-altitude lightning. The modal flash altitude was 10 km, but many flashes occurred at very high altitude (15–20 km). There were also anomalous and stratiform flashes near 5–7 km in altitude. Most flashes were small (<50 km2 area). Comparisons with GLM on 14 and 20 December 2018 indicated that GLM most successfully detected larger flashes (i.e., more than 100 VHF sources), with detection efficiency (DE) up to 90%. However, GLM DE was reduced for flashes that were smaller or that occurred lower in the cloud (e.g., near 6-km altitude). GLM DE also was reduced during a period of OT electrical discharges. Overall, GLM DE was a strong function of thunderstorm evolution and the dominant characteristics of the lightning it produced. 

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2. Huntsville Alabama Marx Meter Array 2: Upgrade and Capability

   https://doi.org/10.1029/2020EA001111  

   Zhu, Yanan; Bitzer, Phillip; Stewart, Michael; Podgorny, Scott; Corredor, David; Burchfield, Jeff; Carey, Lawrence; Medina, Bruno; Stock, Michael (April 2020, Earth and Space Science)

   Abstract The Córdoba Argentina Marx Meter Array (CAMMA), consisting of 10 second‐generation Huntsville Alabama Marx Meter Array (HAMMA 2) sensors, operated at Córdoba, Argentina, during the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign in late 2018. Initial results obtained from the campaign demonstrate that the new sensor is able to provide a significantly more detailed depiction of various lightning processes than its first generation. The lightning flashes mapped by the CAMMA and a colocated Lightning Mapping Array (LMA) were compared. The overall flash structures mapped by the CAMMA and the LMA look similar for most of the flashes. However, comparisons at smaller time scale show that the majority of CAMMA and LMA sources are not concurrent, indicating that unmatched sources were possibly due to different physical processes in leader propagation dominating different frequencies and differences in data processing and location techniques. 

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3. Characterizing Charge Structure in Central Argentina Thunderstorms During RELAMPAGO Utilizing a New Charge Layer Polarity Identification Method

   https://doi.org/10.1029/2021EA001803  

   Medina, Bruno L.; Carey, Lawrence D.; Lang, Timothy J.; Bitzer, Phillip M.; Deierling, Wiebke; Zhu, Yanan (August 2021, Earth and Space Science)

   Abstract A new automated method to retrieve charge layer polarity from flashes, named Chargepol, is presented in this paper. Using data from the NASA Lightning Mapping Array (LMA) deployed during the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign in Cordoba, Argentina, from November 2018 to April 2019, this method estimates the polarity of vertical charge distributions and their altitudes and thicknesses (or vertical depth) using the very‐high frequency (VHF) source emissions detected by LMAs. When this method is applied to LMA data for extended periods of time, it is capable of inferring a storm's bulk electrical charge structure throughout its life cycle. This method reliably predicted the polarity of charge within which lightning flashes propagated and was validated in comparison to methods that require manual assignment of polarities via visual inspection of VHF lightning sources. Examples of normal and anomalous charge structures retrieved using Chargepol for storms in Central Argentina during RELAMPAGO are presented for the first time. Application of Chargepol to five months of LMA data in Central Argentina and several locations in the United States allowed for the characterization of the charge structure in these regions and for a reliable comparison using the same methodology. About 13.3% of Cordoba thunderstorms were defined by an anomalous charge structure, slightly higher than in Oklahoma (12.5%) and West Texas (11.1%), higher than Alabama (7.3%), and considerably lower than in Colorado (82.6%). Some of the Cordoba anomalous thunderstorms presented enhanced low‐level positive charge, a feature rarely if ever observed in Colorado thunderstorms. 

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4. Atmospheric Gamma-ray Observations at the Telescope Array Detector

   https://doi.org/10.1088/1742-6596/2398/1/012008  

   Abbasi, R (December 2022, Journal of Physics: Conference Series)

   Abstract Previously in AtmoHead-2018, we reported joint observations by Telescope Array Surface Detector (TASD), Lightning Mapping Array (LMA), sferic sensor and broadband interferometer of particle showers coincident with lightning. These consisted of energetic showers of approximately less than 10 microsecond duration with footprints on the ground of 3-6 kilometers in diameter, originating in the first one to two milliseconds of downward lightning leaders and coincident with high-current processes within the leaders. Scintillator waveform and simulation studies confirmed that these showers must consist primarily of gamma radiation. On September 11, 2021, atmospheric discharges emitting gamma rays were, for the first time, recorded by a high-speed camera and by lightning detectors on the ground simultaneously. The events were detected by the Telescope Array located in the Utah desert and were filmed by the Phantom v2012 camera, set at an acquisition rate of 40,000 frames per second (fps) in conjunction with the Lightning Mapping Array (LMA), an interferometer, a fast antenna, and the National Lightning Detection Network (NLDN). Results from this study reported the new observation of several events of significantly longer duration and higher uence, bridging the gap between the TASD and satellite-based detections. These events further demonstrate the similarity between the upward and downward TGF varieties and the likelihood of a common origin for their production. 

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5. SAETTA: high-resolution 3-D mapping of the total lightning activity in the Mediterranean Basin over Corsica, with a focus on a mesoscale convective system event

   https://doi.org/10.5194/amt-12-5765-2019  

   Coquillat, Sylvain; Defer, Eric; de Guibert, Pierre; Lambert, Dominique; Pinty, Jean-Pierre; Pont, Véronique; Prieur, Serge; Thomas, Ronald J.; Krehbiel, Paul R.; Rison, William (January 2019, Atmospheric Measurement Techniques)

   Abstract. Deployed on the mountainous island of Corsica for thunderstormmonitoring purposes in the Mediterranean Basin, SAETTA is a network of 12 LMA(Lightning Mapping Array, designed by New Mexico Tech, USA) stations thatallows the 3-D mapping of very high-frequency (VHF) radiation emitted by cloud discharges in the60–66 MHz band. It works at high temporal (∼40 ns in each 80 µs time window) and spatial (tens of meters at best) resolutionwithin a range of about 350 km. Originally deployed in May 2014, SAETTA wascommissioned during the summer and autumn seasons and has now been permanentlyoperational since April 2016 until at least the end of 2020. We firstevaluate the performances of SAETTA through the radial, azimuthal, andaltitude errors of VHF source localization with the theoretical model ofThomas et al. (2004). We also compute on a 240 km × 240 km domainthe minimum altitude at which a VHF source can be detected by at least sixstations by taking into account the masking effect of the relief. We thenreport the 3-year observations on the same domain in terms of number oflightning days per square kilometer (i.e., total number of days during whichlightning has been detected in a given 1 km square pixel) and in terms oflightning days integrated across the domain. The lightning activity is firstmaximum in June because of daytime convection driven by solar energy input,but concentrates on a specific hot spot in July just above the intersectionof the three main valleys. This hot spot is probably due to the low-levelconvergence of moist air fluxes from sea breezes channeled by the threevalleys. Lightning activity increases again in September due to numeroussmall thunderstorms above the sea and to some high-precipitation events.Finally we report lightning observations of unusual high-altitude dischargesassociated with the mesoscale convective system of 8 June 2015. Most ofthem are small discharges on top of an intense convective core duringconvective surges. They are considered in the flash classification of Thomaset al. (2003) to be small–isolated and short–isolated flashes. The other high-altitude discharges, much less numerous, are long-range flashes that developthrough the stratiform region and suddenly undergo upward propagationstowards an uppermost thin layer of charge. This latter observation isapparently consistent with the recent conceptual model of Dye and Bansemer (2019) that explains such an upper-level layer of charge in the stratiformregion by the development of a non-riming ice collisional charging in amesoscale updraft. 

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