A new approach is presented in this work to measure the electrical charge carried by precipitation particles and their corresponding fall velocity. The instrument represents an improved version of our previous device, with the primary goal of increasing the sampling rate of charged droplets to improve and make the statistical analysis of charged raindrops more robust. Additionally, the instrument incorporates a computational program for detecting individual raindrop passages, enabling automatic calculation of its electrical charge and fall velocity. To test the new device’s performance, it was simultaneously used with our previous instrument during a storm in Córdoba on November 21, 2023. It was observed that the latest instrument increased the sampling rate nearly fivefold compared to the old one. The results demonstrate a high degree of consistency across different devices, validating the reliability and reproducibility of the new device.

The “Relámpago del Catatumbo” is a striking phenomenon that occurs over Lake Maracaibo, where the most intense lightning activity on the planet takes place. In this work, we extend the study of lightning activity in Lake Maracaibo and its surroundings, evaluating the period from 2014 to 2024. The results show that the hourly distributions of lightning activity are correlated with the variations of deep convective events in the region; the seasonal variations in lightning strikes are correlated with the monthly variations in the mean water temperature of Lake Maracaibo. These findings suggest that the Lake may be providing the water vapor for the development of storm systems that form in the region. It was found that the diurnal and monthly variations of the lightning activity have not changed substantially over the years, as these variations are, very similar to those found in the period 2005–2010 by Bürgesser et al. (2012), https://doi.org/10.1016/j.jastp.2012.01.013 . The interannual analysis of variations in lightning activity suggests a general increase in the stroke number per year per km 2 across the entire study area (latitudes [6–12] N and longitudes [69–75] W). However, the lightning activity over the Lake exhibits high variability, preventing the identification of a systematic trend.

This study presents evidence of spike formation in droplets freezing on small ice crystals, measuring only a few micrometers in size. Spike formation was exclusively observed on columnar ice crystals formed at approximately −6°C, while no such phenomena were detected on hexagonal plate crystals formed at around −22°C. These findings are in agreement with previous research, which indicates that spike formation requires droplet freezing near the melting point. The formation of spikes during the early riming stages holds significant implications, as these structures can eject new ice particles. This study suggests that the Hallett–Mossop mechanism may activate at the onset of riming, challenging the conventional view that millimeter‐sized graupel particles are necessary for splinter ejection. This mechanism has profound implications for amplifying ice particle concentrations in mixed‐phase clouds, potentially influencing precipitation processes, atmospheric dynamics, and global climate systems.

This study investigates the ionospheric variations resulting from thunderstorms that occurred between 00:00 UTC and 08:00 UTC on November 10, 2018, in the central region of Argentina, site of the RELAMPAGO-CACTI Project (Remote sensing of Electrification, Lightning, and Mesoscale/microscale Processes with Adaptive Ground Observations; Clouds, Aerosols, and Complex Terrain Interactions). The data used were the Total Electron Content (TEC), which was computed from Global Navigation Satellite System (GNSS) measurements provided by the Argentinian Continuous Satellite Monitoring Network (RAMSAC by its Spanish acronym) stations and the atmospheric electrical activity data that were provided by the Earth Networks Total Lightning Network (ENTLN). We observed that the generated disturbances have periods less than or equal to 100 minutes and peak-to-peak DVTEC amplitude values reaching up to 1.35 TECU (1 Total electron content unit =1016electrons/m2). We also noted that these atmospheric gravity waves, which show the highest peak-to-peak amplitudes, occur during periods of intense lightning activity. Finally, we found that for a day with Atmospheric Electrical Activity (AEA), the peak-to-peak amplitudes of the waves are approximately 2.91 times greater than the peak-to-peak amplitudes of a day without AEA.

Raindrop size distributions observed with a particle size velocity disdrometer are contrasted with respect to the size distributions of charged raindrops obtained with a special device designed to determine the size and electric charge of raindrops. The measurements were performed for three thunderstorms occurred in the vicinity of Córdoba, Argentina during RELAMPAGO campaign. In general, the results show that more than 66% of the raindrops measured with the optical disdrometer have diameters <1 mm and more than 90% of the charged raindrops have diameters >1 mm. A systematic difference between both raindrops size distributions was observed, which remains during the whole evolution of the storms. Under the hypothesis that the electrically charged raindrops were melted ice hydrometeors, we analyze if the larger raindrops recorded by the disdrometer during these storms may also have been melted ice particles.

Homogeneous freezing nucleation occurs in supercooled liquid water by the formation of critical-sized ice embryos. Molecular Dynamics simulations were performed 'sowing' a solid embryo into liquid and monitoring the subsequent system evolution. The size of critical ice embryos and the activation energy barrier associated with the incorporation of molecules into the germ were estimated using the TIP5P-E water model for three different temperatures: 237, 240 and 244 K. The results show how MD simulations provide reliable outcomes for the study of both parameters.

Abstract The electrical charge carried by raindrops provides significant information about thunderstorm electrification mechanisms, since the charge acquired by hydrometeors is closely related to the microphysical processes that they undergo within clouds. Investigation of charges on raindrops was conducted during the Remote sensing of Electrification, Lightning, And Meso‐scale/micro‐scale Processes with Adaptive Ground Observations field campaign. A newly designed instrument was used to determine simultaneously the fall velocity and charge for precipitating particles. Hydrometeor size and charge were measured in Córdoba city, Argentina, during electrified storms. Temporal series of size‐charge of single raindrops were recorded for two storms, which were also monitored with a Parsivel disdrometer and Lightning Mapping Array. The results show that the magnitude of the electric charges range between 1 and 50 pC and more than 90% of the charges are mainly carried by raindrops >1 mm, even though most of the raindrops are smaller than 1 mm. Furthermore, the measurement series show charged hydrometeors of both signs all the time. A correlation between the sizes and the charges carried by the raindrops was found in both storms.

This article aims to study the variations that occur in the ionosphere as a consequence of a thunderstorm. For this purpose, we started by analyzing the thunderstorms of November 10 at night in the central region of Argentina, the place and time when the RELAMPAGO-CACTI Project was developed. The data used were The Total electron Content (TEC) which was computed from Global Navigation Satellite System (GNSS) measurements provided by Argentine Continuous Satellite Monitoring Network (RAMSAC by its Spanish acronym) stations and the atmospheric electrical activity data which were provided by the Earth Network Total Lightning Network (ENTLN). We found that thunderstorms generated some oscillations in the vertical total electron content (VTEC). Some variations showed oscillations with periodicities of 25–30 minutes and amplitudes greater than 0.3 total electron content units (TECU). While in other cases oscillatory variations were observed with periods of about 4 minutes and amplitudes around 0.1 TECU. The former could be related to gravity waves, while the latter could be considered acoustic waves.

This article provides an overview of the experimental design, execution, education and public outreach, data collection, and initial scientific results from the Remote Sensing of Electrification, Lightning, and Mesoscale/Microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign. RELAMPAGO was a major field campaign conducted in the Córdoba and Mendoza provinces in Argentina and western Rio Grande do Sul State in Brazil in 2018–19 that involved more than 200 scientists and students from the United States, Argentina, and Brazil. This campaign was motivated by the physical processes and societal impacts of deep convection that frequently initiates in this region, often along the complex terrain of the Sierras de Córdoba and Andes, and often grows rapidly upscale into dangerous storms that impact society. Observed storms during the experiment produced copious hail, intense flash flooding, extreme lightning flash rates, and other unusual lightning phenomena, but few tornadoes. The five distinct scientific foci of RELAMPAGO—convection initiation, severe weather, upscale growth, hydrometeorology, and lightning and electrification—are described, as are the deployment strategies to observe physical processes relevant to these foci. The campaign’s international cooperation, forecasting efforts, and mission planning strategies enabled a successful data collection effort. In addition, the legacy of RELAMPAGO in South America, including extensive multinational education, public outreach, and social media data gathering associated with the campaign, is summarized.

A phenomenon that occurs regularly during explosive volcanic eruptions is the presence of lightning associated with the development of the volcanic plume. Remote detection of these electrical discharges can be helpful in volcanic monitoring. In recent years, the Geostationary Operational Environmental Satellite (GOES-16) satellite has provided information on recorded electrical discharges through its sensor, the Geostationary Lightning Mapper (GLM). This information is in addition to the detection of lightning strokes by ground stations that was already being used for this purpose. In this work we propose to use the data provided by the GLM and the Earth Networks Total Lightning Network (ENTLN) to analyze the electrical activity that occurred during the eruption of the Volcan de Fuego on June 3, 2018

Electrical discharges are observed in many volcanic eruptions and they have often been used as indicators of such eruptions.Volcanic lightning is remarkably similar to those produced during thunderstorms and is called analogous to thunderstorm-like plume lightning.The WWLLN developed a program called "Ash Cloud Monitor" (ACM), in which alerts are issued for possible volcanic eruptions when lightning strokes are detected around a volcano.The ACM tool has demonstrated to be a very effective technique to be aware of volcanic eruptions.However, most of the alerts released by ACM belong to false alarms of volcanic activity, because, in general, the detected lightning is produced by thunderstorms near the volcano.In order to assess and improve the ACM to detect volcanic eruptions, reducing false alert emissions and improving the quick interpretation of them, we develop a web platform called Georayos-VolcanoAr with a new structure and a modified algorithm, with respect to the algorithm used by ACM, for the classification of alerts.The new algorithm considers an alert system with 3 levels: Red -Yellow -Green, with the Red alert being the highest level and decreasing towards Green.The Red alert was assigned to those volcanoes where only recorded lightning within a radius of 20 km or the lightning detected within a radius of 20 km is at least twice as much as that detected up to 100 km from the vent.The study focused on 32 volcanoes located in the Andes, close to the Argentine-Chilean border, and analyzed the results reported by the ACM network in terms of a climatological study of the lightning activity, thunderstorm days and predominant winds in that region.This analysis serves as a basis for a general recognition of the study zone in order to improve the interpretation of the distribution and generation of false alerts; as well as to help decision makers, among others, to have a reference that allows them to issue the warning.

During November 2018-April 2019, an 11-station very high frequency (VHF) Lightning Mapping Array (LMA) was deployed to Cordoba 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 km(2) 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.

This work reports a new laboratory study of the electric charge separated in collisions between a spherical target of 1 cm in diameter growing by riming and vapor-grown ice crystals, with the objective of studying the charging behavior of the larger ice precipitation particles in thunderstorms in terms of the noninductive mechanism. A series of experiments was conducte d for a wide range of environmental conditions; the measurements were performed for effective liquid water content between 0.5 and 5 gm(-3), for ambient temperatures between -5 and -30 degrees C and at air speed of 11 m s(-1). The magnitude and sign of the electric charge transfer on the ice sphere as a function of the ambient temperature and the effective liquid water content is presented. The results show a charge reversal temperature for the riming target, which is roughly independent of liquid water concentration in the measured range. The simulated graupel charges negatively for temperatures below -15 degrees C, and positively at temperatures above -15 degrees C.

During November 2018 through April 2019, an 11-station NASA lightning mapping array (LMA) was installed in the Cordoba region of Argentina, in support of GOES-16 Geostationary Lightning Mapper (GLM) calibration and validation, as well as the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign. This region of Argentina is well known for frequent, intense thunderstorms and severe weather. The LMA was monitored remotely via the Internet throughout its deployment, but due to bandwidth limitations no real-time data were available. Custom GOES-16 imagery provided by NASA SPoRT assisted with monitoring of thunderstorm cases. Occasional site visits were done to obtain data disks, perform routine maintenance, and troubleshoot problems. During the deployment the network captured lightning in a variety of storm modes, including ordinary and severe multicells, supercells, and mesoscale convective systems. Many examples of normal-polarity thunderstorms, as well as a few examples of anomalously charged thunderstorms, were observed. Long (100+ km) horizontally stratified lightning flashes, as well as lightning in overshooting tops, also were frequently observed. Supporting research radar observations were available through January 2019, with operational radar coverage available after that time. Some cases featured supporting ABI meso scanning. This presentation will report on the LMA deployment in context with the RELAMPAGO field campaign, show results from some representative case studies, and will provide initial comparisons to GLM observations.

NASA Marshall Space Flight Center (MSFC) has deployed an electric field meter (EFM) and a Lightning Mapping Array (LMA) to support recent field campaigns. For PISTON (Propagation of Intraseasonal Tropical Oscillations), a ship-based campaign in the Western Pacific Ocean during August-October 2018, NASA MSFC worked in collaboration with Colorado State University (CSU) to deploy an EFM on the R/V Thomas G Thompson (Fig. 1a). This instrument was primarily intended to support intercomparisons with the Carnegie curve, as well as to investigate the role of maritime thunderstorms and electrified shower clouds in maintaining the global electric circuit. Polarimetric C-band weather radar observations were collected along with the EFM observations using the new SEA-POL ship radar developed by CSU. The MSFC LMA is being installed near Cordoba, Argentina (Fig. 1b), in collaboration with University of Alabama in Huntsville (UAH) and the National University of Cordoba (UNC), to support the RELAMPAGO (Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations) campaign, as well as to support ground validation of the Geostationary Lightning Mapper (GLM) instrument. RELAMPAGO is aimed at understanding initiation and upscale growth of convection in Argentina, home to some of the most intense thunderstorms on Earth. The 11-station network will operate during approximately November 2018 through April 2019. Similar to PISTON, the electricity observations will be acquired in the context of multiple radar observations. After all data have been collected and quality controlled, they will be made publicly available on the Internet by NASA MSFC.

RELAMPAGO (Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations) is a National Science Foundation (NSF) field campaign to understand intense and severe convection in central Argentina, near the Sierras de Cordoba mountain range. In order to address RELAMPAGO science goals, as well as to assist with ground validation of the Geostationary Lightning Mapper (GLM) instrument on the GOES-16/17 satellites, NASA Marshall Space Flight Center (MSFC) has installed an 11-station Lightning Mapping Array (LMA) in this region. The LMA supported the Enhanced Observing Period (EOP) of RELAMPAGO, and then is continuing operations until mid-to-late April 2019.

In this work we present the results of experimental measurements of the charge transferred to simulated graupel under wet growth conditions. The range of temperature was between −7 and −18 °C. The speeds of collision employed in the measurements were between 8 and 13 m/s with the goal of representing graupel of different initial densities. The aim of this study was to corroborate the existence of charge transfer under wet growth. The results show the presence of positive charge when graupel reaches partial wet growth, and the magnitude of this charge is comparable to the charge transferred under dry growth conditions. On the other hand, when total wet growth is reached no charge transfer is registered. This leads to the conclusion that the non‐inductive mechanism could be working under partial wet growth conditions when the ice crystals collide with the dry regions of the graupel surface and then bounce off.

This work studies the role of mineral particles collected in the region of Patagonia (Neuquén, Argentina) as ice nuclei particles (INPs) by immersion freezing mode. The particle immersion-freezing ability was analyzed under laboratory conditions by using an established drop-freezing technique. Mineralogical composition was characterized by using X-ray diffraction and electron micro probe analysis. Dynamic light scattering was used to determine the grain size distribution of particles, while the N2 adsorption and methylene blue adsorption methods were applied to determine their specific surface area. Water droplets of different volumes containing different concentrations of particles were cooled until droplets were frozen. For all the analyzed drop volumes, an increase in the freezing temperature of the drops was observed with increasing dust concentration. In the same way, the freezing temperature increased when the drop volume was increased at constant dust concentration. Both behaviors were linked to the availability of active sites in the particles. A plateau in the freezing temperature was observed at high suspension concentration for all the drop volumes. This plateau was related to the aggregation of the particles when the suspension concentration was increased and to the consequent decrease in the number of active sites. The active sites per unit of surface area were calculated and reported. For the studied range of temperature, results are in agreement with those reported for different sites and particles. From the chemical and morphological analysis of the particle components and the results obtained from the literature, it was concluded that even though montmorillonite was the main mineral in the collected sample, the accessory minerals deserve to be analyzed in detail in order to know if they could be responsible for the ability of the collected soil particles to act as INPs. Considering that the region of Patagonia has been identified as an important source of natural mineral particles in the atmosphere, it is important to analyze the ability of these particles to act as INP. As far as we know, this is the first study carrying out this investigation.

In austral spring of 2018, an 11station NASA lightning mapping array (LMA) will be installed in the Cordoba region of Argentina, in support of GOES16/ 17 Geostationary Lightning Mapper (GLM) calibration and validation, as well as the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign. This region of Argentina is well known for frequent, intense thunderstorms and severe weather. Lightning observations in storms that initiate, become severe, and grow upscale are expected to be obtained by GLM and the LMA during the LMA’s multimonth deployment. We hypothesize that, similar to the analogous U.S. High Plains, anomalously charged thunderstorms with frequent inverted lightning at low levels are common in this region, which may have implications for GLM detection efficiency. Deployment logistics and experimental approach will be explained, and some early results from the LMA (including comparison to GLM) will be presented.