NH1.5
Orals: Mon, 24 Apr | Room M2
The ground-level potential gradient atmospheric electric field, the air conductivity, and concentration of cloud condensation nuclei have been recorded at Stanislaw Kalinowski Geophysical Observatory in Świder, Poland (52°07' N, 21°14' E), for several decades. A new digitisation project of Świder atmospheric electric data published in the observatory year books provides an opportunity to review the results of studies of the long-term variation of the electric parameters. New results of an analysis of both short-term and long-term variations in the positive conductivity and related component of the air-Earth current density are presented, and implications for the Global Electric Circuit studies using the Świder dataset are discussed. This work is supported by Poland National Science Centre grant no 2021/41/B/ST10/04448.
How to cite: Odzimek, A., Pawlak, I., and Kępski, D.: Analysis of long-term variations in fair-weather PG, the positive air conductivity and conduction current density at Geophysical Observatory in Świder, Poland, and implications for the Global Electric Circuit, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-977, https://doi.org/10.5194/egusphere-egu23-977, 2023.
Measurements of atmospheric electricity have been made at many sites over a long time, with the vertical Potential Gradient (PG) the most commonly observed quantity. In general, the PG responds to local influences from weather, aerosol effects on charge exchange, and variability in the global atmospheric electric circuit. Different methods have been used to classify PG data, for example through identifying days when conditions were considered relatively undisturbed, or by using meteorological information to identify days on which weather-related variability was negligible. Nevertheless, local effects can persist, especially in data obtained at continental sites. Hence, if long term changes in the global atmospheric electric circuit are to be investigated, the local effects need first to be reduced or, ideally, removed.
Recent work has demonstrated a close relationship between the PG at some sites and ocean temperatures modulated by the El Niño Southern Oscillation, through the associated changes in the global atmospheric electric circuit ([1],[2], [3]). The expectation of such a relationship can be used to test methods of removing and reducing local effects in PG data. A method based on the Carnegie curve – the hourly variation known to be present in the global circuit – is discussed here. Through comparison of hourly PG data from a site with the Carnegie curve, outlier values lying beyond the usual range of global circuit changes can be identified and removed. The remaining data can then be used to construct new daily or monthly averages with reduced local variability, evaluated by comparison with global circuit changes associated with the El Niño Southern Oscillation.
References
[1] R.G. Harrison, K.A. Nicoll, M. Joshi, E. Hawkins: Empirical evidence for multidecadal scale Global Atmospheric Electric Circuit modulation by the El Niño-Southern Oscillation Environ Res Lett 17, 124048 (2022) https://iopscience.iop.org/article/10.1088/1748-9326/aca68c
[2] N.N. Slyunyaev, N.V.I lin, , E.A. Mareev,.G. Price: A new link between El Nino - Southern Oscillation and atmospheric electricity, Environ. Res. Lett., 16, (2021) https://doi.org/10.1088/1748-9326/abe908
[3] R.G. Harrison, M. Joshi, K. Pascoe: Inferring convective responses to El Niño with atmospheric electricity measurements at Shetland Environ Res Lett 6 (2011) 044028 http://iopscience.iop.org/1748-9326/6/4/044028/
How to cite: Harrison, R. G., Nicoll, K., Joshi, M., and Hawkins, E.: Removing local variability from Potential Gradient data – the Carnegie filter, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14440, https://doi.org/10.5194/egusphere-egu23-14440, 2023.
Observed responses of the AC and DC parts of the Global Electric Circuit (GEC) to the large eruption of the Hunga Tonga - Hunga Ha’apai (HT-HH) volcano on 15 January, 2022 are presented. The AC-related investigation is based on Schumann resonance (SR) measurements from the Nagycenk Geophysical Observatory (NCK), Hungary as well as from distant stations on the globe belonging to the HeartMath Institute (https://www.heartmath.org/gci/). The DC-related investigation is based on atmospheric electric potential gradient measurements (PG) from six recording stations in Europe and in the USA. The GLD360 and the WWLLN lightning detection networks were used to characterize lightning activity in the vicinity of the HT-HH island on the investigated day. The peak lightning stroke rate reached 80/s (5000/minute), whereas the average global rate is ~44/s. Lightning discharges occurred in rings around the vent of the volcano. Peak currents and the diameter of the ring of positive and negative polarity lightning strokes varied differently in the main phase of the eruption. At its peak, negative lightning dominated the electric activity in the volcanic cloud.
A global intensification of SR is apparent in connection with the enhanced lightning activity caused by the eruption. The SR data together with the global network observations indicate that the lightning activity in the eruption dominates the naturally occurring global activity for a period of at least one hour. The highly localized increase in lightning activity over HT-HH provides a unique point source of excitation for the SR.
In contrast with the dramatic response of the AC global circuit, the response of the DC GEC to this exceptional eruption is not readily unambiguous in the PG measurements. The observations suggest that impulse-like charging of the GEC by ~15% via -CG lightning strokes took place two times during the eruption. A time constant of 7 or 8 minutes has been inferred for near-surface electric field changes from these enhancements. This could be the first direct measurement of the time constant of the GEC near the Earth’s surface, as well as the first observation of the direct charging of the DC GEC by a single atmospheric electrified source.
How to cite: Bór, J., Bozóki, T., Sátori, G., Williams, E. R., Behnke, S. A., Rycroft, M., Buzás, A., Silva, H. G., Kubicki, M., Said, R., Vagasky, C., Steinbach, P., Szabone André, K., and Atkinson, M.: Immediate effects of the Hunga Tonga - Hunga Ha’apai volcanic eruption on the AC and DC Global Electric Circuits, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6148, https://doi.org/10.5194/egusphere-egu23-6148, 2023.
Existing literature indicates that volcanic lightning occurs during a devastating volcano eruption. However, it is still limited to understanding the volcanic electrification mechanism in nature because of the rarity of the explosive volcano eruption and visible spectrum obstacles from plumes full of dirty ashes. The eruption of the Hunga Tonga–Hunga Haʻapai (HT-HH) submarine volcanoes in the Lau Basin, South Pacific, had an extremely violate surtseyan type eruption on January 15th and generated numerous volcanic lightning. This eruption event provides a great opportunity to explore the electrification and evolution of volcanic lightning.
In this work, more than 40,000 lightning events were detected by the World Wide Lightning Location Network (WWLLN) during the primary eruption on January 15th. At the first stage of the eruption, the geographic distribution of lightning strikes expanded rapidly and isotropically while the eruption column reached a specific altitude. Then a lightning tranquility period occurred subsequently, implying explosive erupting was intermittent. Several explosive sub-eruptions were detected from 04:00Z to 07:00Z, and sub-eruptions' timestamps are highly consistent with seismic data analysis from IRIS. Lightning footprint provided evidence that the HT-HH eruption was a surtseyan eruption unsteady with several quiescent phases separating the explosive stages.
HT-HH is one of the most powerful eruptions of the 21st century and provides a favorable environment for volcanic lightning research. The result of this work can track the immediate eruption by using lightning activities. Moreover, volcanic lightning has a different charging mechanism than general tropospheric lightning. Therefore, many interesting issues can be discussed, such as the volcano eruption's contribution to global electrical circuits or whether volcanic lightning can generate other atmospheric electricity events like TLEs or TGFs.
How to cite: Lin, Y.-C. and Chen, A.: Characteristics of Volcanic Lightning Distribution Generated by Hunga Tonga–Hunga Haʻapai on January 15th, 2022, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4714, https://doi.org/10.5194/egusphere-egu23-4714, 2023.
The three years of IITM LLN lightning observation data are used to determine the seasonal and spatial (over different geographical locations) distribution of the ratio of intra-cloud lightning (IC) to cloud-to-ground lightning (CG) in thunderstorms over the Indian sub-continent. The ratio is high (8-10) in the north-western parts and low (0.3-3) in the north-eastern parts. There is not a prominent latitudinal variation of IC and CG ratio, but a climatological seasonal variability exists all over the regions. In the Pre-monsoon (March to May), the mean ratio is observed at 3.87 with a standard deviation of 0.74, and during Monsoon (June to September), that is 3.01 with a standard deviation of 0.52. Pre-monsoon thunderstorm exhibits more IC discharge comparatively monsoonal thunderstorms; hence IC:CG ratio is also high in pre-monsoon. We have observed that CG lightning is approximately 20% of total lightning in pre-monsoon whereas 25% of total lightning in monsoon all over the Indian region. High CAPE associated with a stronger vertical updraft enhances the cold cloud depth and expands the mixed phase region, which can broaden and uplift the size of the upper positive charge center inside a thunderstorm while the middle negative charge center remains at the same temperature level. Therefore it enhances the occurrence of IC discharge between the upper positive charge center and middle negative charge center, hence increasing the IC:CG ratio of a thunderstorm. The implication of these observed results has the importance of separating CG lightning flash from total and can be used in the numerical model to give a proper prediction of CG lightning in hazard mitigation.
How to cite: Ghosh, R., Pawar, S. D., Hazra, A., and Wilkinson, J.: Seasonal and regional distribution of lightning fraction over Indian Sub-continent, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-58, https://doi.org/10.5194/egusphere-egu23-58, 2023.
Over the last few decades, lightning has been one of the fatal extreme weather phenomena in the Indian subcontinent. Aerosols which act as cloud condensation nuclei (CCN) and ice nuclei (IN) can modify the cloud properties and alter the thermodynamic processes within the deep convective clouds in a way that eventually affects the lightning flash rates associated with thunderstorms. Long-term satellite observations suggest that a maximum number of lightning strikes (40-45 flashes/km2) occur during the pre-monsoon (March-May) and monsoon (June-September) seasons over the Indian subcontinent. We analyzed the lightning data available from satellite observations over two distinctly different climatological regions namely, northeast India and western India. In this study, we evaluate the performance of a numerical weather research and forecasting model (WRF) in reproducing the lighting characteristics over these two regions and further try to understand the sensitivity of simulated lightning flash rates to aerosol characteristics and aerosol-cloud interactions considered in the model.
Two severe lightning episodes which occurred on 5-6 May 2013 and 16 April 2019 over northeast India and western India respectively are chosen as case studies for our model sensitivity experiments. We used Morrison, NSSL & SBM microphysics schemes to understand the capability of bulk and bin schemes in simulating these events. Our results show that SBM (bin) scheme affects lightning flash events more accurately than the other two bulk schemes. Increasing aerosol concentrations, increases the cloud droplet number concentrations, thus influences the collision-coalescence processes thereby increase lightning activity over both regions. To further understand the influence of aerosol size, we used a spectral bin microphysics method with a dry radius range of (0.7nm-12µm), which modified the cloud microphysical features. Changing the number concentration and default size of aerosols also influenced the meteorology and hence the deep convection and thunderstorms occurring over the two selected case study regions. More results with greater details will be presented.
How to cite: Ghoshal Chowdhury, S., Ganguly, D., and Dey, S.: A modeling study on the role of aerosols in modulating the lightning flash rates over two different climatological regions of India, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6397, https://doi.org/10.5194/egusphere-egu23-6397, 2023.
Lightning has been declared as a new Essential Climate Variable by the World Meteorological Organization. Schumann resonance is a valuable parameter to monitor the global lightning activity, thus, the Atmospheric Observation Panel for Climate accepted Schumann resonance (SR) measurements as an emerging tool for studying lightning-related large-scale processes in the atmosphere. Previous studies showed a clear extraterrestrial influence on the SR parameters at different time scales (e.g., solar cycle). For all these reasons, a growing new interest arises in the scientific community to exploit the potential of SR better in gaining more information on electrodynamic coupling mechanisms taking place in the atmosphere. This has motivated the installation of new instruments worldwide to monitor SR measurements.
We performed a multi-station spectral analysis of the SR parameters (frequency and intensity) by using wavelet transformation. SR records from different monitoring sites around the globe were analyzed simultaneously for the first time: Hornsund (~12 years of data) and Belsk (~7 y.) managed by Poland, Rovaniemi and Ivalo in Finland (~16 y.), Eskdalemuir in Scotland (~10 y.), Nagycenk in Hungary (~22 y.), Boulder Creek in USA (~4 y.) and Shillong in India (~9 y.). For all SR sites, the periodicities of 0.5, 1, ~180 and 365-day appeared both in the frequency and the intensity of SR modes. Evidence was also found for the ~27- and ~45-day periods at specific time intervals. Cross-wavelet transform and wavelet coherence analyses were made between SR frequencies and the Kp index, and between SR intensities and Madden-Julian Oscillation index. Time periods of highly coherent 27-day as well as 45-day periodicities were found in the time series of these parameters intermittently. These preliminary results suggest that these periodicities are likely related to the solar rotation and Madden-Julian Oscillation, respectively. A detailed analysis about our findings will be presented and discussed.
How to cite: Tacza, J., Bozóki, T., Satori, G., Bór, J., Neska, A., Raita, T., Beggan, C., Atkinson, M., Kumar Sinha, A., and Rawat, R.: Multi-station observation of periodic variations in long-term Schumann resonance records, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-657, https://doi.org/10.5194/egusphere-egu23-657, 2023.
Lightning acts as a natural antenna radiating electromagnetic (EM) waves in a wide frequency range. In the extremely low frequency (ELF) band (3 Hz - 3 kHz), lightning-induced EM waves suffer very weak attenuation while they propagate in the waveguide formed by the Earth’s surface and the lowest part of the ionosphere. These EM waves can travel around the Earth several times before losing most of their energy. This allows ELF-transients generated by powerful lightning discharges from around the globe to be detected at any observation site. We developed an algorithm that identifies ELF-transients in the broadband recordings at Hylaty, Poland (sampling frequency: 3004.81 Hz, antenna bandwidth: 0.02 Hz to 1.1 kHz) and finds their most probable source lightning discharge in the lightning database of the Word Wide Lightning Location Network (WWLLN) based on the technique described by Bór et al. (2022).
Between July 2020 and April 2021 about 270,000 ELF-transients were found in the records from Hylaty. The most probable source of 160,000 transients was identified in the WWLLN database. Using this data set, we show that the propagation speed of broadband ELF-transients differ significantly when the propagation path is on the dayside or on the nightside of the Earth. It is also demonstrated that for lightning discharges close to Hylaty (d<2Mm), the timing and location accuracy of WWLLN has a large impact on the identification of the lightning source and on the inferred propagation speed. A convolutional neural network, trained with ELF-transients of known source location, was used to determine the distance to the lightning source in cases where the source lightning discharge could not be found in the WWLLN database. The average accuracy of the distance provided by the neural network is 700 km. No significant difference can be seen between the distribution of distances obtained by matching the source lightning stroke in the WWLLN database and that obtained using the neural network-based approach.
Reference:
Bór, J., Szabóné André, K., Bozóki, T., Mlynarczyk, J., Steinbach, P., Novák, A., and Lemperger, I. (2022): Estimating the Attenuation of ELF-Band Radio Waves in the Earth’s Crust by Q-Bursts. IEEE Transactions on Antennas and Propagation, 70, 8. https://doi.org/10.1109/TAP.2022.3161504
How to cite: Bozoki, T., Młynarczyk, J., Bor, J., Kubisz, J., Bozso, I., Horvath, A., Kuslits, L., and Timko, M.: ELF-transients detected in the broadband recordings at the Hylaty station in Poland, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-17102, https://doi.org/10.5194/egusphere-egu23-17102, 2023.
Cirrus clouds provide a significant radiative forcing on the Earth's climate system. The net cloud radiative forcing for cirrus clouds results a warming of the climate. More/less cirrus clouds result in more/less warming of the planet. The moisture for the formation of cirrus clouds in the upper atmosphere is transported there in large part via deep convective storms, many associated with lightning activity and hence defined as thunderstorms. An increasing in cirrus clouds in a warmer atmosphere will amplify the initial warming. This paper looks at the connection in space and time between monthly mean lightning activity observed from the Lightning Imaging Sensor on board the International Space Station (LIS-ISS), and the global monthly mean cirrus cloud cover obtained from the MERRA-2 reanalysis product. The correlation coefficient between the global monthly mean cloud optical thickness (COT) of the cirrus clouds (clouds at altitudes above the 400hPa pressure levels) with the monthly mean lightning flash counts is 0.84, implying that monthly mean lightning can explain 70% of monthly variability of the global high cloud optical thickness. In addition, lightning amount explains nearly 60% of the monthly mean global area coverage of cirrus clouds. Given these statistically significant connections between lightning and cirrus clouds, we propose using global lightning data as an additional tool for monitoring monthly variability of cirrus clouds.
How to cite: Saha, J., Price, C., and Guha, A.: The Role of Global Thunderstorm Activity in Modulating Global Cirrus Clouds, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13197, https://doi.org/10.5194/egusphere-egu23-13197, 2023.
Sea ice in the Arctic grows during each hemisphere’s winter and it retreats in the summer. The highly reflective white surface of sea ice reflects solar energy, cooling the planet. When it melts, the darker ocean absorbs more heat, reinforcing the cycle of melting sea ice. Sea ice plays a critical role in regulating Earth’s climate, and it influences global weather patterns and ocean circulations. One essential feedback in the Arctic is the rise in upper tropospheric water vapor (UTWV) or the specific humidity (SH) that acts as an intense greenhouse gas trapping in additional heat released from the Earth's surface. While temperature change is driven by increasing greenhouse gases, the interannual variability in sea ice can be explained by changes in the UTWV (ASO) at 400mb in the Arctic. Where is this increase in UTWV (400mb) coming from in the Arctic? Thunderstorm activity appears to be increasing in the Arctic in the last decades, and could be a source of the increasing UTWV, and hence the decrease in Arctic sea ice.
How to cite: Guha, A., Saha, J., and Price, C.: Increase in Lightning and Upper Tropospheric Water Vapour Over the Arctic Circle, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14579, https://doi.org/10.5194/egusphere-egu23-14579, 2023.
During the last few years, DWD has developed a pioneering nowcasting procedure (NCS-A) for thunderstorms and strong convection based on intelligent combination of lightning data, satellite information and Numerical Weather Prediction. The atmospheric motion vectors needed for the nowcasting are derived with the optical flow method TV-L1. Version 1 of the method NCS-A is operated 24/7 by DWD, covers the complete geostationary ring and has been very well received by aviation customers. The current developments of the nowcasting method focus on the analysis of life cycles in order to be able to improve the prediction of formation and decay of thunderstorms. This includes analysis of lightning activity. Further, work is also being done to seamlessly extend the forecast times by up to 6-8 hours through ensemble analysis of the Lightning Potential Index, provided by the DWD NWP model ICON. In addition to the mentioned developments of physical methods, research is being also carried out on AI-based methods (neural networks) in cooperation with the University of Mainz. The presentation will start with an overview of the current 24/7 thunderstorm nowcasting. This will be followed by a presentation and discussion of the current developments at DWD aimed at providing accurate 6-8 hour forecasts of thunderstorms. Links for further readings and software will be provided as well.
References:
Müller R, Haussler S, Jerg M. The Role of NWP Filter for the Satellite Based Detection of Cumulonimbus Clouds. Remote Sensing. 2018; 10(3):386. https://doi.org/10.3390/rs10030386
Urbich I, Bendix J, Müller R. Development of a Seamless Forecast for Solar Radiation Using ANAKLIM++. Remote Sensing. 2020; 12(21):3672. https://doi.org/10.3390/rs12213672.
Müller R, Haussler S, Jerg M, Heizenreder D. A Novel Approach for the Detection of Developing Thunderstorm Cells. Remote Sensing. 2019; 11(4):443. https://doi.org/10.3390/rs11040443
Zach, Christopher & Pock, Thomas & Bischof, Horst. (2007). A Duality Based Approach for Realtime TV-L1 Optical Flow. Pattern Recognition. 4713. 214-223. 10.1007/978-3-540-7
Müller, R.; Barleben, A.; Haussler, S.; Jerg, M. A Novel Approach for the Global Detection and Nowcasting of Deep Convection and Thunderstorms. Remote Sens. 2022, 14, 3372. https://doi.org/10.3390/rs14143372
Brodehl, S.; Müller, R.; Schömer, E.; Spichtinger, P.; Wand, M. End-to-End Prediction of Lightning Events from Geostationary Satellite Images. Remote Sens. 2022, 14, 3760. https://doi.org/10.3390/rs14153760
How to cite: Müller, R., Barleben, A., Haussler, S., and Jerg, M.: Short term forecast and monitoring of thunderstorms - status and recent developments at DWD., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1888, https://doi.org/10.5194/egusphere-egu23-1888, 2023.
We study evolution of lightning activity accompanying rapid intensity changes of tropical cyclones worldwide. We use a dataset of 400 tropical cyclones occurring between 2012 and 2017. We use the cyclones tracks from the International Best Track Archive for Clime Stewardship. The lightning data are provided by the World Wide Lightning Location Network (WWLLN). We inspect the lightning activity and median stroke energies accompanying rapid intensifications (RI) of cyclones, defined as increases of the wind speed by more than 30 kt in 24 hours, and their rapid weakenings (RW), defined as decreases of the wind speed by more than 40 kt in 24 hours.
In an area of radial wind maximum (RWM), we observe a stroke density of 15.1 strokes/(100 km)2/hour for RI and 21.8 strokes/(100 km)2/hour for RW, respectively, which is much higher than average RWM density 7.9 strokes/(100 km)2/hour over the duration of the cyclone. A median stroke energy is 0.3 kJ during RI and 0.7 kJ during RW. It means that during rapid intensification of cyclones, there are less strokes with slightly higher energies and during rapid weakening there are more strokes with slightly lower energies. When analyzing the cyclones in both hemispheres separately, we obtain 0.3 kJ for RI and 0.6 kJ for RW in the northern hemisphere, and 0.8 kJ for RI and 0.9 kJ for RW in the southern hemisphere. The difference in the stroke density during RI and RW was observed larger in the northern hemisphere (19.7 vs 34.1 strokes/(100 km)2/hour), when in the southern hemisphere the stroke density is much lower and differs less (4.4 strokes/(100 km)2/hour for RI and 5.1 strokes/(100 km)2/hour for RW).
How to cite: Rosická, K., Kolmašová, I., and Santolík, O.: Evolution of lightning activity observed during rapid intensity changes of tropical cyclones, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6089, https://doi.org/10.5194/egusphere-egu23-6089, 2023.
Knowledge about the occurrence of thunderstorms in polar regions is still limited. Lightning detection systems have varying detection efficiency over time and space, which makes climatological analysis difficult. This is especially problematic in areas where lightning strikes are relatively rare. Traditional observations carried out at weather stations are therefore still a very important source of information about the occurrence of thunderstorms in the polar and circumpolar regions. Scientific studies usually predict that these phenomena will be more frequent in high latitudes in a warmer world. To check whether the number of thunderstorms changes as projected, we summarize SYNOP data from manned World Meteorological Organization (WMO) stations operating in the years 2000-2019 located at latitudes above 60° of both hemispheres. According to this source, the changes in thunderstorm frequency are only visible in certain areas and mostly during the summer months. The regional Kendall test revealed a statistically significant increase in the number of thunderstorm days north of 60°N in Interior Alaska, northwestern Canada, much of Siberia and European Russia. However, a decrease in thunderstorm frequency has also been detected in some regions. This was the case on the shores of the southern Norwegian Sea and seasonally in spring in the northern Urals. The largest increase in thunderstorm days exceeded 5 per decade in the highly continental regions of central Siberia and interior Alaska. For the entire high-latitude area, the change in the number of days with thunderstorms was statistically insignificant. However, the statistically relevant increase in the number of thunderstorm days is visible for inland weather stations located 250 – 1,000 km from the coastline, where it was on average 1 day per decade.
How to cite: Kępski, D. and Kubicki, M.: Changes in thunderstorm activity at high latitudes observed at WMO weather stations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-795, https://doi.org/10.5194/egusphere-egu23-795, 2023.
Far from being a recent development of the Earth System, volcanism has accompanied the Earth, terrestrial planets and countless exoplanets since their origins. Volcanism is a material mechanism whereby planets evolve to their differentiated states that are potentially capable of hosting life. Explosive volcanic eruptions are commonly accompanied by volcanic lightning, modulated by charging and discharging mechanisms within the eruption column. As discharges have been proposed as a potential prebiotic synthesis mechanism for forming first organic molecules, the behaviour of volcanic lightning at early Earth conditions could yield further insights into likely environments for the origin of life.
Earth´s atmosphere has changed significantly in composition and pressure since its early beginnings. Here, we would like to investigate how volcanic lightning might have operated and was influenced by changes in those environmental conditions. For this purpose, we have developed an experimental device, which consists of a gas-tight modification of a shock-tube apparatus, to investigate experimental discharges in decompressed jets of gas and volcanic ash particles under varying atmospheric conditions. The setup acts as a Faraday cage, capable of measuring discharges close to the vent. The gas inside the particle collector tank is sampled by crimp cap bottles and analysed by gas chromatography. We modified the enveloping atmospheric composition and pressure (200 mbar – 4 bar) and the transporting gas phase (argon and nitrogen).
We have tested atmospheres containing carbon dioxide, nitrogen and carbon monoxide to mimic early Earth conditions and obtained discharges with similar magnitude to those achieved in an air atmosphere. We have also varied the atmospheric pressure and observed that decreasing the atmospheric pressure results in less discharges. The results of the experiments demonstrate that it is the coupling between gas and ash particles which largely governs the occurrence and magnitude of discharges close to the jet nozzle. Nitrogen as transporting gas results in fewer discharges compared to argon, emphasizing the importance of the composition of the transporting gas phase in the jet charging and discharging mechanisms. The preliminary results point to active volcanic settings under varying atmospheric conditions as multivariate environment for the emergence of life and thus our experiments continue.
How to cite: Springsklee, C., Scheu, B., Seifert, C., Cimarelli, C., Gaudin, D., Dingwell, D. B., and Trapp, O.: Experimental volcanic lightning under conditions relevant to the early Earth: Discharges as a possible prebiotic synthesis mechanism, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1742, https://doi.org/10.5194/egusphere-egu23-1742, 2023.
Traditional long-range lightning detection and location networks use Time-of-Arrival (TOA) differences, and a single timestamp to locate lightning events. For long propagation distances, the amplitude of ground waves decays faster with distance than sky waves as a result of the ground conductivity and the effects of Earth curvature (Caligaris et al., 2008, Cooray, 2009, Hou et al., 2018). This can lead the skywaves to interfere with their large amplitudes when locating lightning.
Coherency, which is short for phase coherency of the analytic signal, is used here, which exhibits lightning characteristics (Bai & Fullekrug, 2022). This work introduces a simulation study to lay the foundation for new lightning location concepts. A novel interferometric method using coherency is presented here, which expands the use of more data points of recorded lightning sferics to map the lightning into an area in a long-range network. In this map, each pixel corresponds to a lightning location with different coherency and time of arrival differences, simulated by shifting the complex lightning waveforms. In long-range networks, the coherency of the 1st skywave is larger than the ground wave, and it is difficult to distinguish them due to the short time delay between them. One solution is to use a small network so that the recorded waveforms are associated with short propagation distances which can eliminate the interferences caused by the first skywave. Another solution is to filter the data such that a lightning waveform is represented by an impulse. In this case, only one maximum coherency area exists for each event at the lightning occurrence time.
In the future, the data collected with a real-time lightning detection network will be analysed to map the lightning events using the complex interferometric method for use in long-range lightning location networks.
References
Bai, X., & Füllekrug, M. (2022). Coherency of Lightning Sferics. Radio Sci., 57(5), e2021RS007347. doi: 10.1029/2021rs007347
Caligaris, C., Delfino, F., & Procopio, R. (2008). Cooray–Rubinstein Formula for the Evaluation of Lightning Radial Electric Fields: Derivation and Implementation in the Time Domain. IEEE Trans. Electromagn. Compat., 50(1), 194-197. doi: 10.1109/temc .2007.913226
Cooray, V. (2009). Propagation Effects Due to Finitely Conducting Ground on Lightning-Generated Magnetic Fields Evaluated Using Sommerfeld’s Integrals. IEEE Trans. Elec-tromagn. Compat., 51(3), 526-531. doi: 10.1109/temc.2009.2019759
Hou, W., Zhang, Q., Zhang, J., Wang, L., & Shen, Y. (2018). A New Approximate Method for Lightning-Radiated ELF/VLF Ground Wave Propagation over Intermediate Ranges. Int. J. Antennas Propag., 2018(6), 1-10. doi: 10.1155/2018/9353294
How to cite: Bai, X. and Fullekrug, M.: Long-range Lightning Interferometry (A Simulation Study), EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6741, https://doi.org/10.5194/egusphere-egu23-6741, 2023.
Lightning is a ubiquitous source of infrasound, and an essential climate variable. Acoustic measurements have been carried out by the CEA over the last ten years to characterize thunder within the framework of the HyMeX project. First, during the fall of 2012 in the south of France in the Cévennes region during the intensive measurement campaign (SOP1) and more recently, in the fall of 2018 in Corsica (France), as part of the EXAEDRE campaign. During both the SOP1 and EXAEDRE campaigns, mini-arrays (“AA” for “Acoustic Array”) of four microphones (respectively disposed on a 50m and a 30m-wide triangle) were used. Lightning information were available thanks to three kinds of electromagnetic detection systems. Firstly, classical Lightning Location Systems (LLS) measured the low frequency range (1-350 kHz), giving the flash emission time and location, as well as its peak current. Secondly, a network of 12 antennas, Lightning Mapping Array (LMA), detecting in the very high frequency range (60-66 MHz) was used. It measured the radiation from leaders and intracloud discharges, which occur mostly inside the thundercloud, providing the 3D location of these discharges. Thirdly, the Charge Moment Change (CMC) was provided by broadband Extremely Low Frequency (< 1.1 kHz) measurements.
Time delays between AA sensors inform on the direction of sound arrival, while the difference between emission time and sound arrival provides the source distance. Combining the two allows a geometrical reconstruction of individual lightning flashes, each viewed as a set of point sound sources. Co-localization of acoustic sources with in-cloud detections provided by the LMA and with ground impacts provided by the LLS shows the efficiency and precision of the method. The measured sound amplitude can also be back-propagated, compensating for absorption and density stratification. This allows to evaluate the acoustical power of each detected source, and then the total power of an individual flash.
In both campaigns, very heterogeneous geometrical distributions of source sound powers within a single flash are frequently observed. Most of the power is frequently located in only one portion of the lightning, most of the time in the return stroke, but also sometimes in the intracloud part. A few homogeneous cases are observed, especially in SOP1. The total acoustical power of the flashes turns out to be also extremely variable, extending over at least 4 orders of magnitude with a median value of 3 MW. It correlates quite good with the peak current or the CMC, and the nature of the correlation differs strongly with the category of lightning considered, either typical return strokes or very energetic positive flashes generating sprites. However, a high dispersion of the data is observed, so that it is not possible to correctly predict any electrical parameter using only the total acoustic power of an event, although a trend is statistically observed. This could be overcome by finding other variables to fully explain the relationship between acoustical and electrical parameters, and improving our propagation model to better account for acoustic variability.
How to cite: Bestard, D., Farges, T., and Coulouvrat, F.: Localization and quantification of the acoustical power of lightning flashes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6342, https://doi.org/10.5194/egusphere-egu23-6342, 2023.
Global lightning location data has long been a critical tool for lightning research and safety. The Earth Networks Total Lightning Network (TLN) incorporates advanced lightning location technology delivering competitive lightning detection efficiency, location accuracy, and classification (intracloud vs cloud-to-ground). It consists of over 1800 wideband sensors deployed in 40+ countries to detect lightning and generate real-time localized storm alerts. TLN is constantly evolving through network expansion, as well as hardware and software development. In this presentation, we will cover some of the recent advances to the TLN hardware and processor. The new TLN sensor has been redesigned to use a dipole sensing element to help reduce the requirements of a strong ground. These new sensors are currently being used operationally and produce comparable waveforms to the previous monopole antenna. New upgrades to the lightning location algorithm have increased the detection efficiency, location accuracy, and classification accuracy of the network. Globally, TLN is locating approximately 50% more pulses than it was before. In moderately remote regions of the world, performance gains can be higher. TLN continues to use data from the World Wide Lightning Location Network (WWLLN), enhanced via raw signals from approximately 200 TLN sensors, to locate lightning in extremely remote regions like the deep oceans. However, how WWLLN data is incorporated into the TLN feed has changed, leading to significantly reduced false alarm rates in some regions. Location accuracy was improved by developing a new propagation model for signals produced by lightning, resulting in a reduction in location error by as much as a factor of 2. As a result of the improved location accuracy, as well as enhancements to the false alarms rates, there is improved clustering of lightning, which directly impacts downstream products such as lightning alerting and Dangerous Thunderstorm Alerts.
How to cite: DiGangi, E., Lapierre, J., Zhu, Y., and Stock, M.: Earth Networks Lightning System Update, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16886, https://doi.org/10.5194/egusphere-egu23-16886, 2023.
Lightning flashes can produce a discharge in which a continuing electrical current flows for more than 40 ms. Such flashes have been proposed to be the main precursors of lightning-ignited wildfires.
In this work, we used lightning measurements provided by the Geostationary Lightning Mapper (GLM) over the continental United States of America during the summer of 2018 to confirm the role of lightning with continuing currents in the ignition of wildfires. We investigated projections in the occurrence of lightning with continuing currents and in the meteorological conditions that favor wildfires over the next century by applying a new parameterization of continuing currents based on the updraft strength. The simulations are performed by using the European Center HAMburg general circulation (ECHAM) / Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model [1]. We found a 41% increase in the occurrence of lightning with continuing currents worldwide. Increases are largest in South America, the western coast of Northern America, Central America, Australia, Southern and Eastern Asia, and Europe, while only regional variations are found in northern polar forests, where wildfires can affect permafrost soil carbon release.
We obtained a possible increase in the risk of lightning-ignited fires in Europe, Eastern Asia, North America, the Western coast of South America, Central Africa and Australia. In turn, the simulations suggest a decrease in the risk of lightning-ignited wildfires in polar regions of Eurasia and North America. Finally, projections do not show any clear tendency in the Amazon rainforest during the typical fire season.
[1] Pérez-Invernón, F. J., Huntrieser, H., Jöckel, P., and Gordillo-Vázquez, F. J.: A parameterization of long-continuing-current (LCC) lightning in the lightning submodel LNOX (version 3.0) of the Modular Earth Submodel System (MESSy, version 2.54), Geosci. Model Dev., 15, 1545–1565, https://doi.org/10.5194/gmd-15-1545-2022, 2022.
How to cite: Pérez-Invernón, F. J., Gordillo-Vázquez, F. J., Huntrieser, H., and Jöckel, P.: Global occurrence of continuing currents in lightning and lightning-ignited wildfires predicted for the next century, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5302, https://doi.org/10.5194/egusphere-egu23-5302, 2023.
A presence of regular sequences of microsecond-scale pulses has been occasionally reported in the lightning literature for more than forty years. Due to a fine time resolution of modern electromagnetic receivers, the properties of these pulse trains are now well described. Nevertheless, the conditions for their occurrence are still not understood, and the information needed for their proper modelling is not sufficient.
To contribute to this effort, we report for the first time properties of negative recoil stepped leaders accompanied by regular trains of microsecond-scale pulses simultaneously seen by the broadband magnetic loop antenna SLAVIA (Shielded Loop Antenna with a Versatile Integrated Amplifier; 5 kHz-90 MHz), and the radio telescope LOFAR (Low Frequency Array; 30-80MHz). We investigate four pulse trains that occurred during complicated intracloud flashes on 18 June 2021, when heavy thunderstorms hit Netherlands.
The pulses within the trains are unipolar, a few microseconds wide with an inter-pulse interval of about ten microseconds. The pulse trains last from 100 µs to 800 µs. After a careful time alignment of both magnetic field and LOFAR time series, we found that the broadband pulses perfectly match with regularly distributed and relatively isolated bursts of VHF sources localized by the LOFAR impulsive imager. All trains were generated by negative recoil stepped leaders propagating downward (two events) or upward (two events) at altitudes between 5.5 km and 8.5 km. Their tracks were formed by positive leaders occurring within the same flash several hundreds of milliseconds previously. The peak powers of VHF sources seen by the LOFAR electric antennas closest to the investigated discharges were about one order of magnitude higher than the power of signals emitted by normal negative leaders. These stepped recoil leaders propagate at a relatively low speed of about 2-5x10^6 m/s, when similar recoil leaders often reach speeds of 10^7 m/s. The velocity and inter-pulse intervals decrease towards the end of trains.
We show that observed pulse trains are due to stepping recoil leaders. However, we consider this strong pulsing nature of the examined recoil leaders to be quite unusual. The physical mechanism giving rise to the energetic VHF bursts and accompanying regular microsecond-scale pulses remains unclear.
How to cite: Kolmašová, I., Scholten, O., Santolik, O., Hare, B. M., Liu, N. Y., Dwyer, J. R., and Lán, R.: A strong pulsing nature of negative recoil leaders accompanied by regular trains of microsecond-scale pulses , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3801, https://doi.org/10.5194/egusphere-egu23-3801, 2023.
We have used the LOw-Frequency ARray (LOFAR) to search for the growing tip of an intra-cloud (IC) positive leader. LOFAR is an extended astronomical radio telescope consisting of many (thousands antennas arranged is stations operating at very-high frequencies (VHF). For these lightning observations we have used about 170 dual polarized antennas in the Netherlands with baselines up to 100 km.
Even with our most sensitive beamforming method, where we coherently add the signals of all 170 antenna pairs, we were not able to detect any emission from the tip of an IC positive leader. Instead, we put constraints on the emissivity of VHF radiation from the tip at 1 aJ/MHz at 60 MHz, well below the intensity of the galactic background.
We conclude that these IC positive leaders propagate in a continuous process which is in sharp contrast to what is seen to the step-wise propagation seen in some cloud-to-ground positive leaders and for negative leaders.
How to cite: Scholten, O., Hare, B., Dwyer, J., Liu, N., and Sterpka, C.: Searching for the VHF signature of the tip of an intra-cloud positive leader, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11504, https://doi.org/10.5194/egusphere-egu23-11504, 2023.
Orals: Tue, 25 Apr | Room M2
Lightning dart and recoil leaders are difficult to understand, as they have a different (often smoother) propagation mode than stepped leaders, and re-ionize a previously ionized channel. In order to understand them better, we have imaged recoil leaders with the LOFAR radio telescope (30-80 MHz), and will present 3D polarization, speed, and intensity data from multiple recoil leaders. We will show that many recoil leaders with high VHF intensity have VHF polarization that is very parallel to the recoil leader channel, with an opening angle as small as 15 degrees. Recoil leaders with lower VHF intensity have larger polarization opening angles, but it is not clear if this is physical or instrumental. In addition, VHF emission from recoil leaders comes from a sub-meter thin channel. Finally, we will show that the propagation speed and VHF intensity are strongly correlated; almost following a power-law or exponential relationship. These results probe the streamer behavior of recoil leaders, and thus provide significant clues to how recoil and dart leaders propagate. The fact that recoil leaders are very VHF thin is consistent with small polarization opening angles, and demonstrates that recoil leaders have significant streamer activity in their core and their corona sheath is VHF silent. The power-law/exponential relationship between speed and VHF intensity, however, is very difficult to explain.
How to cite: Hare, B., Scholten, O., Buitink, S., Dwyer, J., Liu, N., Sterpka, C., and ter Veen, S.: The propagation and 3D VHF polarization properties of recoil leaders, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12591, https://doi.org/10.5194/egusphere-egu23-12591, 2023.
We delved into the upward negative precursors that occur at the wire tip of the rocket during ascent as well as the initial negative leaders, by analyzing comprehensive data of rocket-triggered positive lightning. Our high vertical resolution current detection identified a significant number of weak current pulses in addition to the typical precursors with peak currents of tens of amperes. These weak pulses could occur as isolated events or could be prior the typical-intensity precursors with a lead time of approximately 20 μs. The typical-intensity precursors created visible discharge channels that can be identified using optical means. The development of those clustered precursors featured step-wise channel extensions that were consistent with the initial sustained upward leaders, with an average 2-D speed of around 105 m/s. The temporal and spatial relationship of adjacent precursor-producing channels was analyzed. After the extinction of the previous precursor channel, a new one formed at the apex of the previous channel as the triggering wire tip arrived there. The study confirmed that the precursors were actually un-sustained leader development, which produced initial leader channel segment at the triggering wire tip but eventually extinguished due to the insufficient conditions. The sustained upward negative leader development signified the successful triggering of the lightning. The leader propagated in distinct step-wise manner with average 2-D velocity of 1.85×105 m/s. For a total of 132 steps captured by the highspeed video camera, the step lengths ranged from 0.8 m to 8.7 m, with an average of 3.9 m. During the initial stage of the upward negative stepped leader, there was a notable impulse feature in both the current and electromagnetic field. The equivalent linear charge density of a single step was 118.5 µC/m. The branching of the leader channel typically occurred in connection with the stepping process in two ways. The first involved creating multiple connections between clustering space stems/space leaders and the leader head within a single step. This resulted in a multi-peak current waveform with a peak interval of roughly 2-3 µs (up to 6-7 µs). The second involved reactivating previously extinguished space stems/space leaders and connecting them to the lateral surface of the channel.
How to cite: Jiang, R., Qie, X., Liu, M., Zhang, H., Sun, Z., Yuan, S., Chen, R., Ren, Y., and Liu, K.: Characteristics of upward negative precursor and initial leader development in rocket-triggered positive lightning , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-17026, https://doi.org/10.5194/egusphere-egu23-17026, 2023.
Negative streamers play an important part in propagation of a negative stepped leader. They are emitted from the tip of a space stem or, as a streamer burst, from the tip of the space leader right after its attachment to the main leader.
In the laboratory conditions, it was shown that negative streamers need a significantly higher voltage for inception than positive streamers [e.g., Briels et al, 2008, doi:10.1088/0022-3727/41/23/234004]. The higher negative threshold is in agreement with the higher field measured inside streamer channels, namely 13±2 kV/cm for negative streamers versus 5 kV/cm for positive streamers.
We obtain the conditions for propagation of negative streamers using the Streamer Parameter Model (SPM) [Lehtinen, 2021, doi:10.1007/s11141-021-10108-5]. In this model, we calculate various streamer parameters from relationships between them, with the assumption of maximization of streamer velocity. This model, in the positive streamer case, was shown to agree well with both experimental measurements and hydrodynamic simulation results [Lehtinen and Marskar, 2021, doi:10.3390/atmos12121664]. In the negative streamer case, we show that the parameter equations have no solution below certain background electric fields. The threshold at which the negative streamer appears is around 12-14 kV/cm for 5-10 cm streamer length, which agrees with the experimental data. We also perform hydrodynamic simulations of negative streamers as another way to calculate the conditions for negative streamer propagation.
There is an important difference from positive streamers, for which the propagation threshold is determined by the rate of free electron removal from the streamer channel (i.e., attachment): namely, we find that the negative streamer threshold field is finite even in the absence of the electron removal.
How to cite: Lehtinen, N.: Conditions for inception and propagation of negative streamers, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5529, https://doi.org/10.5194/egusphere-egu23-5529, 2023.
ELVES are transient ring-shaped emissions occurring in the ionosphere above thunderstorms. Multi-ELVES are events consisting of two and up to four rings of light separated temporally by tens of microseconds. The Fluorescence Detector (FD) at the Pierre Auger Observatory has been detecting ELVES with a dedicated trigger since 2013. The high temporal resolution of 100 ns of the FD allows us to record the phototraces of the events in great detail. From the improved processing of the phototraces, we have observed ELVES with double and triple peaks. In fact, during the period 2014-20, about 27% of the events detected at Auger are multi-ELVES. The origin of multi-ELVES is still not fully understood, therefore in this work, we tested two models: the first one relates the temporal difference between two peaks (ΔT) to the rise (tr) and fall (tf) times of the current density pulse of the source beam; the second one relates the height of the intra-cloud lightning source (hb) to ΔT and is used to study events with three or more peaks. From the first model, we can obtain combinations of tr and tf where ΔT tends to zero, i.e. the origin of the simple ELVES can also be explained. For this analysis, we compare the ELVES parameters measured in Auger with the lightning properties detected by Earth Networks, i.e. the location, waveform, and height of these sources.
How to cite: Vásquez Ramírez, A., Mussa, R., and Núñez, L. A. and the Pierre Auger Collaboration: Study of multiple ELVES at the Pierre Auger Observatory, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7176, https://doi.org/10.5194/egusphere-egu23-7176, 2023.
The presence of transient corona discharges occurring in thunderclouds has been suspected for a long time. Thunderstorm coronas can be observed as Blue LUminous Events (BLUEs) formed by a large number of streamers characterized by their distinct 337 nm light flashes with negligible (or absent) 777.4 nm optical emission (typical of lightning leaders). The Modular Multispectral Imaging Array (MMIA) of the Atmosphere-Space Interaction Monitor (ASIM) has successfully allowed us to map and characterize BLUEs worldwide. The results presented here include a global analysis of key properties of BLUEs such as their characteristic rise times and duration, their depth with respect to cloud tops, vertical length and number of streamers. We present two different global annual average climatologies of BLUEs depending on considerations about the rise time and total duration of BLUEs worldwide [1-3].
We found that around 10 % of all detected BLUEs exhibit an impulsive single pulse 337 nm light curve shape. The rest of BLUEs are unclear (impulsive or not) single, multiple or with ambiguous pulse shapes. BLUEs exhibit two distinct populations with peak power density < 25 μWm−2 (common) and ≥ 25 μWm−2 (rare) with different rise times and durations. The altitude (and depth below cloud tops) zonal distribution of impulsive single pulse BLUEs indicate that they are commonly present between cloud tops and a depth of ≤ 4 km in the tropics and ≤ 1 km in mid and higher latitudes. Impulsive single pulse BLUEs in the tropics are the longest (up to about 4 km height) and have the largest number of streamers (up to approximately 3 × 109).
[1] S. Soler, F. J. Pérez-Invernón, F. J. Gordillo-Vázquez, A. Luque, D. Li, A. Malagón-Romero, T. Neubert, O. Chanrion, V. Reglero, J. Navarro-González, G. Lu, H. Zhang, A. Huang, N. Ostgaard.: "Blue optical observations of narrow bipolar events by ASIM suggest corona streamer activity in thunderstorms" (Editor's Hightlight), Journal of Geophysical Research - Atmospheres, vol. 125, 2020, doi: 10.1029/2020JD032708.
[2] S. Soler, F. J. Gordillo-Vázquez, F. J. Pérez-Invernón, A. Luque, D. Li, T. Neubert, O. Chanrion, V. Reglero, J. Navarro-González, N. Ostgaard.: "Global Frequency and Geographical Distribution of Nighttime Streamer Corona Discharges (BLUEs) in Thunderclouds", Geophysical Research Letters 2021, 48, doi: 10.1029/2021GL094657.
[3] S. Soler, F. J. Gordillo‐Vázquez, F. J. Pérez‐Invernón, A. Luque, D. Li, T. Neubert, O. Chanrion, V. Reglero, J. Navarro-González, N. Østgaard.: "Global distribution of key features of streamer corona discharges in thunderclouds". Journal of Geophysical Research: Atmospheres, vol. 127, 2022, doi: 10.1029/2022JD037535.
How to cite: Gordillo-Vazquez, F. J., Soler, S., Pérez-Invernón, F. J., Luque, A., Li, D., Neubert, T., Chanrion, O., Reglero, V., Pérez-Navarro, J., and Ostgaard, N.: Worldwide distributions and key properties of Blue LUminous Events (BLUEs) as detected by ASIM, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2026, https://doi.org/10.5194/egusphere-egu23-2026, 2023.
The Atmosphere-Space Interactions Monitor (ASIM) on the International Space Station (ISS) observes lightning and Transient Luminous Events (TLEs) above the thunderstorm clouds. ASIM includes three photometers that sample at 100 kHz and two cameras that image at 12 frames per second. The photometers measure part of the far ultraviolet (FUV) and middle ultraviolet (MUV) band at 180 – 300 nm, a line of the second positive system of N2 at 337nm (blue) and an atomic oxygen line at 777.4 nm (red). The cameras measure in the blue and red bands of the photometers with a spatial resolution on the ground around 400 m × 400 m. When ASIM is in a nadir-viewing configuration, photometer signals in the blue and red are sometimes associated with coincident UV signals, indicating that the UV photons originated from lightning discharges at cloud altitudes and not from the TLEs at higher altitudes. Here, we analyse the optical properties of these events by combining data from ASIM, the global lightning network GLD360, Lightning Mapping Arrays (LMAs) and NEXRAD radars. Of the 12 cases identified with such data coverage, 5 are Cloud-to-Ground (CG) and 7 are Intra-Cloud (IC) lightnings. The lightning leaders are located nearby the cloud top boundaries or partly exposed outside the cloud. Both the CG and IC lightnings are associated with the exposed lightning leaders. The 5 CG lightnings are identified as the “bolts from the blue”, and the 7 IC lightnings are “cloud-to-air” lightning. The altitudes of the sources vary from 5 km to 7 km for the CG lightnings and from 7 km to 15 km for the IC lightnings. The optical properties for the events, such as their irradiance, rise time and duration in the different optical bands are summarized and discussed. The results provide information that allows to estimate the global occurrence of “bolts from the blue” and “cloud-to-air” lightning.
How to cite: Li, D., Neubert, T., Chanrion, O., Husbjerg, L. S., Luque, A., Zhu, Y., Østgaard, N., and Reglero, V.: Optical properties of the shallow and exposed lightning discharges observed by ASIM, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9041, https://doi.org/10.5194/egusphere-egu23-9041, 2023.
Elves are produced when electromagnetic pulses from lightning interact with the lower parts of the ionosphere and are observed from space as expanding rings of light in the UV and visible optical bands. Elves are known to be associated with high peak current lightning. Using data from the Modular Multi-spectral Imaging Array (MMIA) instrument of the Atmosphere-Space Interactions Monitor (ASIM) payload, we search for observations of Elves when high peak currents (>70 kA) are detected by the global ground-based lightning detection network GLD360. We identify two types of events; high peak current detections associated with Elves, and high peak current detections not associated with Elves. To understand why some high peak current discharges do not generate observable Elves, we explore the number of lightning discharges and their peak currents leading up to the events. Preliminary results indicate that for current pulses with peak currents below 100 kA we observe a significant number of Elves, but this quantity depends on the lightning activity within 5 minutes before. Current pulses with peak currents above 120 kA nearly always produce Elves, regardless of the preceding lightning activity.
How to cite: Bjørge-Engeland, I., Østgaard, N., Marisaldi, M., Luque, A., Mezentsev, A., Lehtinen, N., Chanrion, O., Neubert, T., and Reglero, V.: Detections of high peak current lightning and observations of Elves, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9415, https://doi.org/10.5194/egusphere-egu23-9415, 2023.
The Pierre Auger Observatory, the largest cosmic-ray detector in the world, has been
observing peculiar events which are very likely downward TGFs. Their experimental
signature and their time evolution are very different from those of a shower produced
by an ultra high energy cosmic ray. The TGF-like events happen in coincidence with
lightning and low clouds and their deposited energy at the ground is compatible with
that of a standard downward TGF with the source at few kilometers above the
ground. The surface detector (SD) of the Auger Observatory consists of 1660 water-
Cherenkov detectors (WCDs) spread over 3000 km2 in the Argentinian pampa. The
WCD height of 1.2 m makes them highly sensitive to gamma rays and the large area
covered with SD allows us to sample the TGF beam from different points. The
timing shape of WCD signals can be very important to constrain different TGF source
models. Cold runaway from the high fields near the leader tips or relativistic
feedback produce the same energy spectrum but predict a different rise and fall of the
counts versus time, and they could produce a different angular distribution.
Comparisons between simulations and data will be shown.
Moreover, first results from a preliminary analysis of the available meteorological
data at the time of Auger TGF-like events will be presented. Little is known about the
TGF-producing storms. The characteristics of these thunderstorms are being
investigated by studying meteorological data in coincidence with upward TGFs. A
similar analysis is important to better understand downward TGF production
mechanisms and investigate if are the same as those producing upward TGFs.
How to cite: Colalillo, R., Dwyer, J., Smith, D. M., and Ortberg, J. and the Pierre Auger Collaboration: Studying downward TGFs with the largest ground array of gamma-ray detectors, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15378, https://doi.org/10.5194/egusphere-egu23-15378, 2023.
In the first two years of ASIM operations from June 2018 till the end of 2019 486 TGFs have been observed, with a TGF rate of 0.84 per day. Their geographical distribution is consistent with the three main lightning chimneys Central America, Central Africa, and South East of Asia. Figure 1 displays the ISS footprint positions when the TGFs were detected.
Figure 1: ISS position for the 2018-2019 ASIM TGFs. Red circles marked those within 4 minutes of the previous TGF detected.
If the TGF occurrence follows a stochastic process (each TGF is not related to the next one), the time-difference distribution between a TGF detection and the next one should fit an exponential distribution. For a Δt < 4 minutes the number of TGFs following the exponential distribution is 16. Opposite we got 85 in groups of 2-3 TGFs displayed in Figure 1 in red circles. Analyzing the apparent strong discrepancy in the number of detection in less than 4 minutes (Figure 2) and the number derived from the exponential distribution is one of the motivations of this study.
We build a grid of variable dimension cell size to keep the same ISS observing time for each cell in a Monte Carlo code to simulate the TGF generation that has into account the frequency and the anisotropy distribution of the TGFs over the earth.
To preserve the total number of TGF observed in Δt < 4 minutes we need to add a parameter related to the “Storm Activity” defined as the time in a cell available to generate a TGF. The model fits observations when this parameter is 7%±1%. The good correlation between model/observation is displayed in Figure 2.
Figure 2: The predicted distribution of the TGF pairs (Orange) in 15s bins fits the observations (Blue).
The scope of this work is to check the adopted “Storm Activity” value using WWLLN sferics database as a good indicator of storm activity.
How to cite: Navarro-González, J., Connell, P., Eyles, C., Reglero, V., López, J. A., Montanyà, J., Marisaldi, M., Mezentzev, A., Lindanger, A., Sarria, D., Østgaard, N., Chanrion, O., Christiansen, F., and Neubert, T.: TGFs - "Storm Activity" relationship , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15876, https://doi.org/10.5194/egusphere-egu23-15876, 2023.
The Airborne Lighting Observatory for FEGS and TGFs (ALOFT) is a field campaign focused on observing Terrestrial Gamma-ray Flashes (TGFs) and gamma-ray glows from thunderclouds. ALOFT will be flown on a NASA ER-2 research aircraft, flying at 20 km altitude, and the payload includes:
1) Fly’s Eye GLM Simulator (FEGS), an array of imaging photometers as well as different wavelengths, and electric field change meters.
2) Lightning Instrument Package (LIP), giving three component electric field measurements.
3) Several gamma-ray detectors covering four orders of magnitude dynamic range in flux as well as the full energy range for TGF/gamma-ray glow detection.
ALOFT is scheduled for July 2023, with 50 flight hours based out of Florida. Flying over thunderstorms in Central America and Caribbean, one of the most active TGF regions on the planet during the most optimal season, the ALOFT campaign will help us to answer the questions:
1) How and under what conditions are TGFs produced?
2) How extended in space and time are the gamma-ray glows?
To answer question 1), the ALOFT campaign will be supported by ground based radio measurements from different locations in Central America and Caribbean.
To answer question 2), with realtime downlink of data we will know when the ER-2 encounters gamma-ray glowing thunderclouds, and we will instruct the pilot to have the aircraft perform have repeated overflights over this cloud as long as the glow exists, to answer question 2). This will also help us understand whether gamma-ray glows and TGFs are interrelated.
The full set of observational goals of ALOFT are:
1. Observe TGFs in one of the most TGF-intense regions on the planet.
2. Observe gamma-ray glows in thunderstorms and their relation to TGFs.
3. Perform International Space Station Lightning Imaging Sensor (ISS LIS) and Global Lightning Monitor (GLM) validation using improved suborbital instrumentation (including upgraded FEGS).
4. Evaluate new design concepts for next-generation spaceborne lightning mappers.
5. If relevant instrumentation is available, make measurements useful to advance convection science from a suborbital platform.
In this presentation we will give the status and plans for the ALOFT mission.
How to cite: Ostgaard, N., Marisaldi, M., Ullaland, K., Yang, S., Hasan Qureshi, B., Søndergaard, J., Mezentsev, A., Sarria, D., Lehtinen, N., Lang, T., Christian, H., Quick, M., Blakeslee, R., Grove, J. E., and Shy, D.: The ALOFT mission: a flight campaign for TGF and gamma-ray glow observations over Central America and the Caribbean in July 2023, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3116, https://doi.org/10.5194/egusphere-egu23-3116, 2023.
ELVEs are quickly expanding rings of light emissions excited in the lower ionosphere by the electromagnetic pulse of an electric discharge in a thundercloud. They are commonly observed from space platforms and have been reported in conjunction with other atmospheric-electricity events. One motivation to investigate ELVEs is that their signal may provide insight into the discharge that created them. Until now the modeling of ELVES has either relied on strong simplifications or on the Finite-Difference Time-Domain (FDTD) method to directly solve the Maxwell equations. One limitation of the latter is that non-axisymmetrical discharges (with a slanted channel or a non-vertical magnetic field for example) require computationally expensive, fully three-dimensional meshes, which makes parametric studies of the ELVE features slow and cumbersome. We show here that elementary electromagnetic theory allows one to model ELVEs, even non-axisymmetrical ones, with sufficient accuracy at little computational cost. We then apply our methods to the parametric study of ELVE photometric waveforms as recorded by space-based instruments.
How to cite: Luque Estepa, A., Bjørge-Engeland, I., Li, D., Østgaard, N., and Marisaldi, M.: Investigating ELVE photometric waveforms with elementary electromagnetics, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16046, https://doi.org/10.5194/egusphere-egu23-16046, 2023.
K-changes are step-like electrostatic field changes, which occur during the final part of cloud flashes or between the return strokes in cloud-to-ground discharges. We numerically solve the full set of Maxwell’s equations coupled to the electrostatic Poisson’s equation for a given thundercloud charge structure to model the K-changes. We simulate the K-changes by a sequential increase of conductivity of the decayed vertical channel. This process creates a current pulse which attenuates as it propagates downward. We show how the modeled linear charge densities and electric potentials connected to K-changes evolve in time. We successfully compare our model with the electric field measured by a flat-plate E-change antenna with a sensor having a decay time constant of 1 s, a bandwidth of 0.16 Hz –2.6 MHz, and a sampling rate of 5 MS/s. The experimental data used for comparison with our model were obtained at KSC Florida in 2011.
How to cite: Kaspar, P., Marshall, T., Stolzenburg, M., Kolmasova, I., and Santolik, O.: Electrodynamic model of K-changes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3124, https://doi.org/10.5194/egusphere-egu23-3124, 2023.
It is not new knowledge that whistler are always present in the ionosphere during the thunderstorms. The terrestrial ionosphere is mainly a plasma region which is very sensitive for different disturbances. A wide range of plasma instabilities can develop in this region, which are often nonlinear processes and leading to the development of plasma turbulence. Turbulence is one of the most universal events phenomena in nature. It plays a crucial role in the dynamics of the space plasma processes. The turbulence appears when some physical parameter exceeds a certain level. It can have place during strong thunderstorms. The ionosphere is sometimes treated as plasma physics laboratory with unique possibility to study fundamental plasma processes. The use of ionospheric satellite gives the chance to perform insitu measurement of plasma parameters during dynamic processes. For our analysis we used set of selected data of the electric and magnetic fields variations in ELF and VLF ranges originating from the all French microsatellite DEMETER which was operating on the circular orbit with inclination of about 800 at altitude of 660 km from July 2004 until December 2010.
The Fourier, wavelet and bispectral analysis of these signals has been performed. The 3 waves processes has been identified during few very strong strokes. In some cases the nonlinear interactions of whistlers with VLF signals of ground based transmitters. The character of spectra suggests the presence of Richardson’s cascade. Our conclusion is that these results are related to whistler turbulence.
How to cite: Blecki, J., Wronowski, R., and Jujeczko, P.: The nonlinear interactions of whistlers in the ionospheric plasma during strong thunderstorms, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9989, https://doi.org/10.5194/egusphere-egu23-9989, 2023.
Terrestrial gamma-ray flashes (TGFs) are bursts of energetic X- and gamma-rays emitted from thunderstorms and observed by the Atmosphere-Space Interactions Monitor (ASIM) mounted onto the International Space Station (ISS) detecting TGFs and optical signatures of lightning. ISS-LIS (Lightning Imaging Sensor) detects lightning flashes allowing for simultaneous measurements with ASIM. Whilst ASIM measures ~300-400 TGFs per year, ISS-LIS detects ~ 106 annual lightning flashes giving a disproportion of four orders of magnitude. Hence, based on the temporal evolution of lightning flashes and their spatial pattern, we present an algorithm to reduce the number of flashes potentially associated with TGFs by ~90%, and we use the ASIM TGF list to ensure that the resulting flashes are those associated with TGFs and thus benchmark our algorithm. We will compare how the radiance, footprint size and the global distribution of lightning flashes of the reduced set relates to the average of all measured lightning flashes. Finally, we will present a parameter study of our algorithm and discuss which parameters can be tweaked to maximize the reduction efficiency whilst keeping those flashes associated to TGFs. In the future, this algorithm will hence facilitate the search for TGFs in a reduced set of lightning flashes.
How to cite: Köhn, C., Heumesser, M., Chanrion, O., Reglero, V., Østgaard, N., Christian, H., Lang, T., Blakeslee, R., and Neubert, T.: Employing Optical Lightning Data to identify lightning flashes associated to Terrestrial Gamma-ray Flashes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1480, https://doi.org/10.5194/egusphere-egu23-1480, 2023.
As part of the Alpbach Summer School, a collaboration between FFG, ESA and ISSI, a team of students developed the F-class CASPER mission concept to investigate Transient Luminous Events (TLEs) and Terrestrial Gamma Ray Flashes (TGFs). These lightning-related plasma phenomena, first detected on Earth in 1989, typically occur in the mesosphere at an altitude between 50-100 km. The UVS instrument onboard the JUNO mission detected several similar events on Jupiter, and they are expected to also occur on other planets.
The CASPER mission consists of two identical spacecraft, each of which will be equipped with three cameras in different wavelengths and four high speed sensors, the latter will function as triggers to start the data acquisition of higher resolution images. A system chosen to combat the transient characteristic of the events (lifetime < 300 ms). While three sensors will be taking measurements of photons, one will quantify the electron flux in order to constrain the role of TLEs and TGFs in the global electric circuit.
The second great area of interest is the vertical structure of TLEs as well as their global distribution and occurrence rates. To achieve this, data will be captured using a two-satellite train in a sun-synchronous low earth orbit. The orbit is inclined at 98° and the satellites are phased at an angle of 5.2° to observe these events from two points of view simultaneously. The operational mission lifetime is five years, with a possible extension.
How to cite: Maurer, M., Byrne, L., Falk-Petersen, U., Hamdoun, A., Hénaff, G., Huber, K., Ilas, A., Reisinger, N., Sinjan, J., Suarez, C., Szilágy-Sándor, A., Tarvus, V., Tsindis, M., and Vaganov, M.: CASPER: A Space Mission Concept to Investigate Transient Luminous Events and Terrestrial Gamma Ray Flashes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12033, https://doi.org/10.5194/egusphere-egu23-12033, 2023.
Posters on site: Mon, 24 Apr, 14:00–15:45 | Hall X4
We present an analysis of the evolution of PG during the course of rain, hail and snow events at the Xanthi site, N. Greece. In particular, using data from eight rain events in 2021, four hail events in the period 2018-2021 and four snow events during the same period, we examine how the PG frequency distribution changes during the progression of these events and discuss potential implications for the charge of the hydrometeors and the clouds that produce them. We also present some first results from measurements of PG and lightning at the high altitude (2340 m ASL) site of Helmos Observatory, Peloponnese, Greece.
How to cite: Kourtidis, K., Misios, S., Karagioras, A., and Kosmadakis, I.: Measurements of PG during rain, hail, snow and lightning, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1492, https://doi.org/10.5194/egusphere-egu23-1492, 2023.
The generation and variation of the atmospheric electric field (hereafter E-field), which exists under all meteorological conditions and drives the charge flow around the Earth globally, and many natural phenomena such as lightning, thunderstorms, and even earthquakes have been observed accompanied by surface E-field disturbances; therefore, E-field observations are also used in disaster warnings. Since 2021, a ground E-field network consisting of three stations using in-house electric field mills has been deployed in the Tainan area, covering two known seismic faults, to monitor the characteristics of the e-field variation caused by diurnal cycle, thunderstorms, and earthquake precursor.
The results indicated that the small-area E-field variation did not follow the Carnegie curve because local effects (aerosols, weather conditions, and environment) masked the variations of the global electrical circuit. In addition, the analysis of the disturbed E-field showed that more than 90% of the single-cell thunderstorms observed in the surface E-field could be classified as mature and dissipating stages. Each disturbance lasted approximately 34 minutes and was accompanied by an average of 1.4 times E-field phase reversals. Among them, the negative reversal of the surface electric field caused by the negative charge layer was relatively strong and frequent. Eventually, triangulation was used to reconstruct the charge structure of four distinctive single-cell thunderstorm events and restore the surface E-field responses during the passage of clouds. The correlation coefficients between the simulation and the observation were higher than 85%, and the trajectory and speed of the thunderclouds is also successfully reproduced by the recorded e-field data. Furthermore, some preliminary conclusions about earthquake precursors were drawn by analyzing the surface E-field.
How to cite: Chen, A. B.-C. and Chuang, C.-W.: The charge structure of thunderstorms revealed by the ground electric field monitoring network deployed in Tainan, Taiwan, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6527, https://doi.org/10.5194/egusphere-egu23-6527, 2023.
The ground-level atmospheric potential gradient (PG) has been measured with a radioactive collector method in Stanislaw Kalinowski Geophysical Observatory in Świder, Poland, for several decades. The observations have been previously analysed by Kubicki et al. (ICAE 2003, ICAE 2007) revealing rather typical behaviour in the diurnal and seasonal variations of the PG of a land station controlled by pollution. Electric field measurements at such station usually show a maximum at local winter months which are mostly affected by anthropogenic pollution. The whole series has been newly analysed to describe the Świder PG variations in greater detail, also in connection with an analysis of simultaneous measurements of cloud condensation nuclei. Fair-weather potential gradient course is calculated in different time scales (annual, seasonal and diurnal) with taking into account local meteorological and air pollution conditions. An attempt is made to calculate the diurnal and seasonal variations at very low cloud condensation nuclei counts. The work is supported by Poland National Science Centre grant no 2021/41/B/ST10/04448.
How to cite: Pawlak, I., Kępski, D., Tacza, J., and Odzimek, A.: New analysis of diurnal and seasonal variations in fair-weather atmospheric potential gradient and cloud condensation nuclei measured in S. Kalinowski Geophysical Observatory in Świder, Poland, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-978, https://doi.org/10.5194/egusphere-egu23-978, 2023.
For almost a decade, ground-based measurements of the electric field (Ez) have been conducted continuously at Tel-Aviv University's Wise astronomical observatory, located in the Negev desert highland in southern Israel. The data enabled identifying the characteristics of Ez in fair weather, during dust storms, lightning activity and the passage of different cloud types overhead. We present new results of observations of the variability of the atmospheric electric field during several foggy days along with meteorological data of wind speed and relative humidity. The results show a substantial increase of the electric field (up to 400-650 V m-1) compared with the mean fair-weather values at the site (180-190 V m-1) during times of high values of relative humidity (>95%) and low wind speed (<3 m s-1). This increase is a consequence of the reduction in the conductivity at low levels due to the attachment of ions to fog droplets. We suggest that closely monitoring the electric field when there is a forecast for the occurrence of fog can offer a precise indication when fog begins and ends.
How to cite: Yair, Y., Yaniv, R., and Price, C.: The effects of fog on the atmospheric electrical field close to the surface, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3432, https://doi.org/10.5194/egusphere-egu23-3432, 2023.
The use of very low frequency (VLF) radio waves for monitoring the lower part of ionosphere (D region) has contributed immensely to explore this unique domain as satellites and other ground-based instrumentations have not been able to physically assess and characterized it. Several deployed ground- and space-based observational techniques not only enhance a robust capability to monitor, model and predict processes in the atmosphere-ionosphere-magnetosphere coupled regions, but also act as key feature to perform scientific studies in geo-sciences related areas. Here, we present preliminary results from multi-dimensional analyses of LF broadband measurement conducted from Ariel University (AU), Israel, as a complementary useful data source to other available ground- and space- based observational tools, already deployed. The AU LF (0.50 – 470 kHz) observational site, receives electromagnetic waves from different worldwide VLF transmitters as well as other natural sources such as lightning discharges. The station data is mainly used for diagnostic probing of ionospheric irregularities, caused by space weather events such as gamma-ray burst and EUV radiation, along with additional atmospheric electricity measurements. Additionally, different Machine Learning (ML) are used to study spheric waveforms in order to infer their exact location along with different physical characteristics.
How to cite: Ajakaiye, M. P., Reuveni, Y., and Romano, B.: Multi-dimensional Analyses of the First Measurement from the Low Frequency (LF) Radio Waves Receiving Station at Ariel University, Israel, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10903, https://doi.org/10.5194/egusphere-egu23-10903, 2023.
Long continuing current (LCC) lightning flashes contain a discharge in which a continuing electrical current flows for more than 40 ms. They represent about 10% of the total cloud-to-ground lightning flashes and have been associated with lightning-ignited wildfires. LCC flashes can be detected by different terrestrial- and space-based instruments. However, those instruments simultaneously detect all kinds of lightning across the globe, including those with long continuing current, which hinders the analysis of LCC-only events.
We present a method to match every single flash from the Geostationary Lightning Mapper (GLM), the Atmosphere-Space Interactions Monitor (ASIM) and the Earth Networks Total Lightning Network (ENTLN) by using a proximity index. In turn, we analyze the optical signal of LCC flashes simultaneously detected by GLM and ASIM.
According to preliminary results, we found an average of 15 LCC events per month in the continental United States simultaneously detected by the three mentioned sensors (GLM, ASIM and ENTLN). Moreover, this method can be used to match other atmospheric electricity phenomena simultaneously detected by different ground and/or space-based instruments.
How to cite: Camino-Faillace, P. A., Pérez-Invernón, F. J., Gordillo-Vázquez, F. J., Neubert, T., Reglero, V., and Ostgaard, N.: Simultaneous detection of long continuing current lightning with space and ground-based detectors, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5231, https://doi.org/10.5194/egusphere-egu23-5231, 2023.
We analyze the lightning activity over central Europe from 2017 to 2022 using the optical data from the Lightning Imaging Sensor (LIS) on board the International Space Station (ISS). The area of interest covers a central European region limited by 54.5° N, 7.5° E and 44.5° N, 22.5° E. A total number of 68192 lightning flashes was detected during 1805 ISS orbital overpasses. This study compares the lightning activity in central Europe to the global lightning activity and investigates the impact of the COVID-19 pandemic. While there is a global reduction of the lightning activity during the lockdowns in 2020, no significant decrease is observed in central Europe.
On the territory of Czechia, the highest density of flashes was detected in the northwestern part of the country. We combine the ISS-LIS data with measurements of the Shielded Loop Antenna with Versatile Integrated Amplifier (SLAVIA) detectors located in this region. The measurements of the ISS-LIS and SLAVIA detectors are combined with data from the World Wide Lightning Location Network (WWLLN) or Global Lightning Dataset (GLD360) in order to understand the correlation between electromagnetic radiation from selected lightning flashes and their optical characteristics observed from space.
How to cite: Kolínská, A., Kolmašová, I., Price, C., and Santolík, O.: Lightning activity over central Europe in years 2017-2022 (analysis of ISS-LIS data) , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3546, https://doi.org/10.5194/egusphere-egu23-3546, 2023.
Based on data obtained by the Earth Networks Total Lightning Network (ENTLN) for 5 winter seasons (DJF, 2018-2022), the flash density of lightning striking the water surface of the eastern Mediterranean Sea up to 50 km from the Israeli coastline is on average 3 strokes/km2. Out of the total lightning that strike the sea surface in the said area, about 0.05% on are superbolts with peak current > 200 kA. Cloud-to-water strikes generate thunder and underwater acoustic noise that can propagate for a few km from the strike location. While anthropogenic noises have been shown to cause negative stress responses in the marine environment and specifically in aquaculture fish cages, no stress response of cultured fish due to lightning strikes have been recorded yet. New areas in the Israeli territorial waters are allocated to fish farms. These commercial farms will be using net cages, with high fish density expecting large yields.
This research aims to find out how cultured fish respond to the acoustic noises generated by lightning strikes. This hypothesis meets a growing awareness in the aquaculture field to research fish stress that, in this case, stay trapped in the water body without the ability to effectively respond and flee lightning strikes. Continual stress of cultured fish can economically adversely affect the fish farm due to high mortality rates and decreased growth rates. By monitoring sea bream (Sparus aurata) cages, with cameras and hydrophone, during winter months of years 2021-2023, we have found several cases of stress related behavior. These cases were correlated with precise lightnings data, videos of surveillance cameras pointed toward the fish farm, audio records of underwater sound and indications of abnormal fish behavior (sudden dive or direction changes). We will present results from newly developed image processing algorithm that reads underwater fish videos files and automatically finds abnormal behavior events.
How to cite: Asfur, M., Lavie, R., Silverman, J., Price, C., Korzets, M., and Yair, Y.: Effects of cloud-to-water lightning strokes on open sea fish cages during eastern Mediterranean winter thunderstorms, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4086, https://doi.org/10.5194/egusphere-egu23-4086, 2023.
We developed a cloud electrification model (CEM) which describes the evolution of the electric field in clouds, including electric discharges. Our CEM simulates evolution of charge of individual hydrometeors (cloud droplets, rain droplets, ice, snow, graupel) and models the distribution of positive and negative ions. Using this model, we compared the evolution of electric charge and electric field for selected winter and summer thunderstorms that occurred close to the Milešovka meteorological observatory. We analysed the dataset of thunderstorms using measurements of Ka-band cloud profiler and X-band weather radar, both located at the Milešovka observatory, and standard meteorological measurements. The analyses include a comparison of the structure of the modelled thunderstorms with the structure derived from radar and satellite observations.
How to cite: Popová, J. and Sokol, Z.: Modelling of cloud electrification, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13117, https://doi.org/10.5194/egusphere-egu23-13117, 2023.
This study investigates the structure of strong convective storms to determine the difference between the structure of storms inducing or not lightning discharges. The structure of strong convective storms is investigated using a Ka-band Doppler polarimetric vertical cloud profiler operating at a frequency of 35 GHz. The profiler is located at the Milešovka meteorological observatory in Czechia (Central Europe). To study the structure of storms, we used the basic radar measurements of phase and power spectra of the co- and the cross-channel. We analysed the data from all the storms that occurred close to the Milešovka observatory during 2018-2022 and we performed statistical and correlation analyses of vertical profiles of phase and power spectra in the co- and the cross-channel in dependence on the distance of lightning discharges observed and recorded by the EUCLID lightning network.
How to cite: Sokol, Z., Popová, J., and Skripniková, K.: Analyses of thunderstorm structures using data of a Ka-band Doppler polarimetric vertical cloud profiler, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6099, https://doi.org/10.5194/egusphere-egu23-6099, 2023.
ALOFT (Airborne Lightning Observatory for FEGS and TGFs) is a flight campaign designed to observe Terrestrial Gamma-ray Flashes (TGF) and gamma-ray glows close to their production source. The campaign consists of 50 flight hours of a NASA ER-2 research aircraft taking off from Florida and is scheduled for July 2023. The ER-2 cruise altitude of 20 km allows flying over active thunderstorms in the Gulf of Mexico and Caribbean region, one of the most TGF-active region on the planet. The main challenge for TGF detection at close distance is the large variability in the expected gamma-ray flux, spanning four orders of magnitude depending on the radial distance from the source. To cope with this challenge, the ALOFT gamma-ray payload consists of several detectors of different size, made of different materials and readout sensors, designed to cover 4 orders of magnitude dynamic range on the typical TGF/gamma-ray glow energy range (~100 keV - ~40 MeV). In addition, the payload includes the Fly’s Eye GLM Simulator (FEGS), an array of imaging photometers sensitive at different wavelengths, and electric field change meters, and the Lightning Instrument Package (LIP), giving three component electric field measurements. The synergy between airborne gamma-ray, optical and electric field measurements, combined with ground-based radio observations, will provide a unique set of observations to constrain the source properties and their physics. This presentation will focus on the ALOFT scientific payload and the system architecture.
How to cite: Marisaldi, M., Østgaard, N., Ullaland, K., Yang, S., Qureshi, B. H., Søndergaard, J., Mezentsev, A., Sarria, D., Lehtinen, N., Lang, T. J., Christian, H., Quick, M., Blakeslee, R., Grove, J. E., and Shy, D.: The scientific payload of the ALOFT mission to chase Terrestrial Gamma-ray Flashes and gamma-ray glows, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9381, https://doi.org/10.5194/egusphere-egu23-9381, 2023.
The technical purpose of THOR-DAVIS is to test a new camera concept in space for observations of thunderclouds and their electrical activity at up to a resolution of 10 µs. The scientific purpose is to conduct video camera observations of thunderclouds and their electrical activity. The focus is on altitude-resolved measurements of activity at the top of the clouds and the stratosphere above. The camera type is a so-called neuromorphic camera (or event camera) where pixels are read out asynchronously when the pixel illumination changes. The goal is to understand, under realistic conditions, the use of such a camera for future use in space for observations of processes in severe electrical storms. The camera has a high temporal resolution 100.000 equivalent frame per second and a huge dynamic range of about 120 dB and is particularly well suited for this kind of observations. The camera weights about 200g and consumes about 1.5A in operation and is particularly well suited for space applications.
In this presentation we will give the status of the development of the THOR-DAVIS experiment to be conducted by the Danish astronaut Andreas Mogensen during his upcoming ESA mission Huggin onboard the International Space Station (ISS). We’ll present the design of the payload based on a Davis 346 neuromorphic camera mounted on top of a Nikon D5 camera for handheld operation. The 2 cameras are controlled by an AstroPi unit based on a Raspberry Pi computer board.
Finally, we’ll give preliminary results of laboratory measurements made with the flight model.
How to cite: Chanrion, O., Pedersen, N., Stokholm, A., Hauptmann, B., and Neubert, T.: THOR-DAVIS: A neuromorphic camera to observe thunderstorms from inboard ISS., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15873, https://doi.org/10.5194/egusphere-egu23-15873, 2023.
Being one of the natural hazards and an indicator of severe weather, studying and evaluating lightning activity has a well recognized role in scientific research. The detection of lightning activity with a good efficiency is crucial not only to the protection of human lives and minimizing economic losses, but to get a better understanding of Earth’s climate system as well.
There are several solutions for lightning detection implemented both on ground (e.g., Earth Networks, EUCLID, LINET, WWLLN, etc.) and in space (e.g., GLM, LIS, OTD) providing a big amount of reliable data. The BlitzOrtung (BO) is a dynamically developing and community-based lightning detection network (Wanke et al., 2014). By 2018, the BO had circa 2000 stations around the globe (Narita et al., 2018) and their data are used widely in Europe. However, there is a need to evaluate the detection efficiency and compare the parameters of the detected lightning strokes with the ones derived from other networks (Narita et al., 2018).
In this study, we aim at evaluating the performance of the BO network on a statistical basis. First, the detected lightning strokes are paired with those reported by the LINET and WWLLN systems using the time point and location information. Then the geographical distribution as well as the temporal stability of the number of detected events and the percentage of paired events are examined. The first results of a pilot analysis over Hungary (45.5°-49° N, 16°-23° E) in Central Europe will be presented. This project serves to establish a comparison-based method for the evaluation of the lightning climatology of a region.
Narita, T. et al. (2018): A study of lightning location system (Blitz) based on VLF sferics, 34th International Conference on Lightning Protection, 978-1-5386-6635-7/18/$31.00,
Wanke, E., Andersen, R., and Volgnandt, T. (2014): A World-Wide Low Cost Community-Based Time-Of-Arrival Lightning Detection and Lightning Location Network, http://www.blitzortung.org/Documents/TOA_Blitzortung_RED.pdf
How to cite: Buzás, A., Bozóki, T., and Bór, J.: Community-based lightning detection in Europe: studying the detection efficiency of the BlitzOrtung network - a case study concerning lightning climatology over Hungary, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14243, https://doi.org/10.5194/egusphere-egu23-14243, 2023.
The Atmosphere-Space Interactions Monitor (ASIM) is a mission of the European Space Agency launched in April 2018 and hosted onboard the International Space Station (ISS). ASIM is dedicated to study the physics of Transient Luminous Events (TLEs) and Terrestrial Gamma-ray Flashes (TGFs) and their relation to lightning. TGFs are X- and Gamma-ray flashes associated to lightning discharges, with average duration of few tens of microseconds and energies up to 40 MeV. ASIM detects TGFs by means of the Modular X- and Gamma-ray Sensor (MXGS). So far, the MXGS performance (efficiency, effective area) have been evaluated by Monte Carlo simulations only, while energy calibration is monitored using built-in radioactive sources and background lines. TGFs are local events, very rarely observed by more then one spacecraft simultaneously, therefore it is difficult to use them to validate the MXGS performance. Goal of this study is to use cosmic Gamma-ray Bursts (GRBs) simultaneously detected by ASIM and other spacecraft as calibration sources to validate the spectral performance of MXGS. GRBs are the brightest explosions in the universe, associated to the collapse of massive stars or the merger of compact objects, involving at least one neutron star, at cosmological distances. During the period from June 2018 to December 2021, 12 GRBs were detected by ASIM and by one or more other spacecraft. Here we use data from the Konus-WIND mission and from the Fermi Gamma Burst Monitor (GBM), both considered as benchmarks in the field of GRB analysis. We cross-correlate the light curves of the three instruments, and we perform simultaneous spectral analysis using the forward-folding approach. In some cases, we find good consistency between the detectors, indicating an overall validation of the MXGS performance. In other cases, we identified discrepancies, possibly due to absorption from structures of the ISS, currently under investigation. In this presentation, we show our data sample, the methodology used and the preliminary joint spectral analysis results. This work is relevant because it will provide an independent assessment of the MXGS performance, with clear implications for ASIM TGF results.
How to cite: Ramsli, A., Marisaldi, M., Tsvetkova, A., Guidorzi, C., Sarria, D., Mezentsev, A., Lindanger, A., Østgaard, N., Neubert, T., Reglero, V., Svinkin, D., Lysenko, A., and Frederiks, D.: Validation of the ASIM MXGS performance using cosmic Gamma-Ray Bursts, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14736, https://doi.org/10.5194/egusphere-egu23-14736, 2023.
Gamma-Ray Glows (GRGs) are bursts of high-energy radiation that are emitted by thunderclouds and have a duration of seconds to minutes. These radiation sources are extended over several to tens of square kilometers. GRGs have been observed from detectors on the ground, in aircraft, and on balloons. In this paper, we present a Monte-Carlo model that can be used to study the production and propagation of GRGs. We compare our model to one developed by Zhou et al. (2016) and find small differences between the two. We have also created a library of simulations that is available to the community. Using this library, we were able to reproduce five previous GRG observations from five airborne campaigns: balloons from Eack et al. (1996) and Eack et al. (2000), and aircraft from the ADELE (Kelley et al. 2015), ILDAS (Kochking et al. 2016), and ALOFT campaigns (Østgaard et al. 2019).
Our simulation results confirm that the flux of cosmic-ray secondary particles at a given altitude can be enhanced by several percent or even several orders of magnitude due to the effect of thunderstorms' electric fields. These results explain the five observations we studied and will be useful for the upcoming ALOFT-2023 campaign. While some GRGs can be explained solely by the MOS process, the strongest GRGs observed require electric fields significantly larger than the RREA threshold value (E_th). Some of the observations also came with in-situ electric field measurements that were always lower than E_th, but these measurements may not have been taken from the regions where the glows were produced. This study supports the idea that some thunderstorms must have electric fields with magnitudes of at least E_th on a kilometer scale.
References :
-Effect of near-earth thunderstorms electric field on the intensity of ground cosmic ray positrons/electrons in tibet. Zhou et al. (2016). https://doi.org/10.1016/j.astropartphys.2016.08.004
-Balloon-borne x-ray spectrometer for detection of x-rays produced by thunderstorms. Eack et al. 1996. https://doi.org/10.1063/1.1146959
-Gamma-ray emissions observed in a thunderstorm anvil. Eack et al. 2000. https://doi.org/10.1029/1999GL010849
-Relativistic electron avalanches as a thunderstorm discharge competing with lightning. Kelley et al. 2015. https://doi.org/10.1038/ncomms8845
-In-Flight Observation of Gamma Ray Glows by ILDAS. Kochkin et al. 2017. https://doi.org/10.1002/2017JD027405 -Gamma Ray Glow Observations at 20-km Altitude. Østgaard et al. 2019. https://doi.org/10.1029/2019JD030312
How to cite: Sarria, D., Østgaard, N., Marisaldi, M., Lehtinen, N., and Mezentsev, A.: Library of simulated gamma-ray glows and application to previous airborne observations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3281, https://doi.org/10.5194/egusphere-egu23-3281, 2023.
We present the largest catalogue compiled to date of TGFs and associated lightning activity, geostationary satellite cloud images and ERA5 reanalysis data. The TGFs are observed from AGILE, ASIM, FERMI and RHESSI, and the lightning activity by the WWLLN and GLD360 networks. The 1582 TGF events identified are analysed and contextualized relative to lightning flashes. In our analysis, we consider the proportion of TGFs and lightning coming from overshooting tops, and the dependencies on Cloud Top Temperature (CTT) and the Convective Available Potential Energy (CAPE). We find that TGFs come from primarily higher cloud tops than lightning flashes, consistent with previous studies. We also find that CAPE is similar for TGF and lightning-producing cells, and that the proportion of TGF and lightning-producing cells in the overshooting phase are similar. We analyse the regional and seasonal differences between TGFs and lightning and see that regional meteorological effects dominate.
How to cite: Husbjerg, L., Neubert, T., Chanrion, O., Marisaldi, M., Stendel, M., Kaas, E., Østgaard, N., and Reglero, V.: Characterization of Thunderstorm Cells Producing Observable Terrestrial Gamma Ray Flashes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9459, https://doi.org/10.5194/egusphere-egu23-9459, 2023.
In this presentation we will provide an overview and present preliminary results from a multi-institutional collaborative project, which seeks to detect gigantic jets over hemispheric scales using a combination orbital and ground-based sensors and machine learning. Gigantic jets are a type of transient luminous event (TLE, Pasko 2010, doi: 10.1029/2009JA014860) that escape the cloud top of a thunderstorm and propagate up to the lower ionosphere (80-100 km altitude), transferring tens to hundreds of Coulombs of charge. Our detection methodology primarily uses the Geostationary Lightning Mapper (GLM), which is a staring optical imager in geostationary orbit that detects the 777.4 nm (OI) triplet commonly emitted by lightning (Goodman et al. 2013, doi: 10.1016/j.atmosres.2013.01.006). Gigantic jets have been shown to have unique signatures in the GLM data from past studies (Boggs et al. 2019, doi: 10.1029/2019GL082278; Boggs et al. 2022, doi: 10.1126/sciadv.abl8731). Thus far, we have built a preliminary, supervised machine learning model that detects potential gigantic jets using GLM, and begun development on a series of vetting techniques to confirm the detections as real gigantic jets. The vetting techniques use a combination of low frequency (LF) and extremely low frequency (ELF) sferic data, in combination with stereo GLM measurements. When our detection methodology grows in maturity, we will deploy it to all past GLM data (2018-present), with the potential to detect thousands of events each year, allowing correlation with other meteorological and atmospheric measurements. We will share the database of gigantic jet detections publicly during and at project conclusion (2025), allowing other researchers to use this data for their own research.
How to cite: Boggs, L., Smith, J., Mach, D., Cummer, S., Trostel, J., Burke, J., and Losego, J.: Project JetNet: Hemispheric-scale gigantic jet detection network, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16868, https://doi.org/10.5194/egusphere-egu23-16868, 2023.
Posters virtual: Mon, 24 Apr, 14:00–15:45 | vHall NH
Terrestrial gamma-ray flashes (TGFs), bursts of X- and gamma-rays, are emitted from thunderstorms and are produced through relativistic electrons through the Bremsstrahlung process. Despite recent progress through measurements and simulations, the specific mechanism of electron acceleration remains unknown. As the processes inside thunderclouds occur on a multiscale level, we need to develop models that cover a wide range of temporal and spatial scales. As a first step, we here present a GPU based Monte Carlo particle-in-cell code to simulate electron avalanches and streamers, benchmarked against existing particle models. We will present this benchmarking as well as details on the GPU-code implementation as well as first results of electron avalanches and streamers and compare runtimes with previous models. This code will form the basis for a fully hybrid code running on the newest generation of pre-exascale computers. In the future, such a code will allow us to gain insight on the mechanisms responsible for TGFs.
How to cite: Fangel-Lloyd, E., Dujko, S., Karlsson, S., Gammelmark, M., Rydahl, A., Nishikawa, K., and Köhn, C.: Towards a GPU based particle model for streamer discharges, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7235, https://doi.org/10.5194/egusphere-egu23-7235, 2023.
The atmosphere is made slightly electrically conductive by cosmic rays and natural radioactivity, which generate ions. Air conductivity is a key component of the global electric circuit and influences droplet and cloud charging [1]. Further, atmospheric ions may affect the radiative balance through particle formation and infra-red absorption [2], [3]. Both considerations motivate the need for accurate atmospheric ion measurements. The Programmable Ion Mobility Spectrometer (PIMS) is a computer-controlled instrument based on the Gerdien measurement principle in which a cylindrical capacitor, across which a voltage is applied, is aspirated to sample air ions [4]. Computer control of a switchable multimode electrometer [5] offers the capability to measure ions in two modes, offering self-calibration, which removes the difficulties with providing a well-characterised environment for calibration [6]. The PIMS can independently monitor internal leakage currents which can be a significant source of thermally dependent error, especially in outdoor use. First developed in the early 2000s, the PIMS has recently been modernised with a new electrometer and advanced microcontroller, leading to significantly miniaturised electronics and opportunities for more sophisticated interfacing. The modernised PIMS was tested at Nagycenk Geophysical Observatory (47.632°N,16.718°E), Hungary in summer 2022, alongside a full range of meteorological and atmospheric electrical measurements for comparison.
References
[1] R. G. Harrison and K. A. Nicoll, “The electricity of extensive layer clouds,” Weather, vol. 77, no. 11, pp. 379–383, Nov. 2022, doi: 10.1002/wea.4307.
[2] K. L. Aplin, “Composition and measurement of charged atmospheric clusters,” Space Sci Rev, vol. 137, no. 1–4, 2008, doi: 10.1007/s11214-008-9397-1.
[3] K. L. Aplin and M. Lockwood, “Cosmic ray modulation of infra-red radiation in the atmosphere,” Environmental Research Letters, vol. 8, no. 1, 2013, doi: 10.1088/1748-9326/8/1/015026.
[4] K. L. Aplin and R. G. Harrison, “A computer-controlled Gerdien atmospheric ion counter,” Review of Scientific Instruments, vol. 71, no. 8, 2000, doi: 10.1063/1.1305511.
[5] R. G. Harrison and K. L. Aplin, “Multimode electrometer for atmospheric ion measurements,” Review of Scientific Instruments, vol. 71, no. 12, 2000, doi: 10.1063/1.1327303.
[6] K. L. Aplin and R. G. Harrison, “A self-calibrating programable mobility spectrometer for atmospheric ion measurements,” Review of Scientific Instruments, vol. 72, no. 8, 2001, doi: 10.1063/1.1382634.
How to cite: Aplin, K., Meaney, A., Bór, J., and Buzás, A.: Development and testing of a modernised Programmable Ion Mobility Spectrometer, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13985, https://doi.org/10.5194/egusphere-egu23-13985, 2023.
TGFs being the bursts of high energy photons shot from Earth’s atmosphere to space, are known to be produced during the initial upward propagation of the +IC lightning leader. VLF and LF radio sferics can often be found in association with the short duration TGFs. The Atmosphere-Space Interactions Monitor (ASIM) instrument provides synchronous X- and gamma-ray measurements with optical recordings in 180-240 nm, 337 nm and 777.4 nm wavelength. This allows for simultaneous detection for TGFs and the lightning processes associated with them.
ASIM TGF observations have shown that TGFs within the FOV of the optical instruments are always accompanied by the prominent optical pulse which starts the lightning flash. TGFs have a clear tendency to slightly precede the optical pulse, but the short duration of TGFs together with the optical delay of the lightning light propagating through the cloud do not allow to confidently resolve the true sequence of these events.
The same problem is present in radio measurements: radio signature from TGF current is usually mixed with lightning current in the recordings due to temporal proximity of the processes involved.
Here we report a remarkable, high fluence and long duration TGF, together with its associated optical recordings. This observation shows clear distinction between the TGF and the associated optical pulse: the optical pulse is subsequent to the TGF, as it starts after the TGF is terminated. This allows to conclude that strong current surges inside the leader channel are not responsible for the TGF generation, and, in turn, the current surge producing the optical pulse can be conditioned by the generated TGF, or even be responsible for TGF termination.
How to cite: Mezentsev, A., Østgaard, N., Marisaldi, M., Neubert, T., Chanrion, O., and Reglero, V.: Discerning TGF and Leader Current Pulse in ASIM Observation, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11467, https://doi.org/10.5194/egusphere-egu23-11467, 2023.
