Gobal and regional chemical influence of sprites: Reconciling modeling results and measurements

Mesospheric electrical discharges, known as sprites, formed by fast-propagating streamers, have been shown to create localized enhancements of atmospheric constituents such as N, O, NOx, N2O, and HOx, as indicated by both, modeling results and space-based measurements. In this study, we incorporate the occurrence rate of sprites into a chemistry-climate model using meteorological parameters as a proxy. Additionally, we introduce the injection of chemical species by sprites into the model, based on electrodynamical modeling of individual sprite streamers and observations from space. Our modeling results show a good agreement between the simulated sprite distribution and observed data on a global scale. While the global influence of sprites on the atmospheric chemistry is found to be negligible, our findings reveal their measurable chemical influence at regional scale, particularly for the concentration of HNO3 and HNO4 within the mesosphere. The simulations also suggest that sprites could be responsible for the observed NO2 anomalies at an altitude of 52 km above thunderstorms, as reported by MIPAS. Finally, a projected simulation reveals that the occurrence rate of sprites could increase at a rate of 14 % per 1 K rise in the global temperature

Variation of lightning-ignited wildfire patterns under climate change

Lightning is the main precursor of natural wildfires and Long-Continuing-Current (LCC) lightning flashes are proposed to be the main igniters of lightning-ignited wildfires (LIW). Previous studies predict a change of the global occurrence rate and spatial pattern of total lightning. Nevertheless, the sensitivity of lightning-ignited wildfire occurrence to climate change is uncertain. Here, we investigate space-based measurements of LCC lightning associated with lightning ignitions and present LCC lightning projections under the Representative Concentration Pathway RCP6.0 for the 2090s by applying a recent LCC lightning parameterization based on the updraft strength in thunderstorms. We find a 41% global increase of the LCC lightning flash rate. Increases are largest in South America, the western coast of North America, Central America, Australia, Southern and Eastern Asia, and Europe, while only regional variations are found in northern polar forests, where fire risk can affect permafrost soil carbon release. These results show that lightning schemes including LCC lightning are needed to project the occurrence of lightning-ignited wildfires under climate chang

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)

Lightning flashes can produce a discharge in which a continuing electrical current flows for more than 40 ms. Such flashes are proposed to be the main precursors of lightning-ignited wildfires and also to trigger sprite charges in the mesosphere. However, lightning parameterizations implemented in global atmospheric models do not include information about the continuing electrical current of lashes. The continuing current of lightning flashes cannot be detected by conventional lightning location systems. Instead, these so-called long-continuing-current (LCC) flashes are commonly observed by extremely low-frequency (ELF) sensors and by optical instruments located in space. Reports of LCC lightning flashes tend to occur in winter and oceanic thunderstorms, which suggests a connection between weak convection and the occurrence of this type of discharge

Different Types of Corona Discharges Associated With High-Altitude Positive Narrow Bipolar Events Nearby Cloud Top

Single- and multi-pulse blue corona discharges are frequently observed in thunderstorm clouds. Although we know they often correlate with Narrow Bipolar Events (NBEs) in Very Low Frequency/Low Frequency radio signals, their physics is not well understood. Here, we report a detailed analysis of different types of blue corona discharges observed by the Atmosphere-Space Interactions Monitor during an overpass of a thundercloud cell nearby Malaysia. Both single- and multi-pulse blue corona discharges were associated with positive NBEs at the top of the cloud, reaching about 18 km altitude. We find that the primary pulses of multi-pulse discharges have weaker current moments than the single-pulse discharges, suggesting that the multi-pulse discharges either have shorter vertical channels or have weaker currents than the single-pulse discharges. The subsequent pulse trains of the multi-pulse discharges delayed some milliseconds are likely from horizontally oriented electrical discharges, but some NBEs, correlated with both single-and multi-pulse discharges, include small-amplitude oscillations within a few microseconds inside their waveforms, which are unresolved in the optical observation and yet to be understood. Furthermore, by jointly analyzing the optical and radio observations, we estimate the photon free mean path at the cloud top to be ∼6 m. © 2023. The Authors.This work was supported by the European Research Council (ERC) under the European Union H2020 programme/ERC Grant agreement 681257. It also received funding from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant agreement SAINT 722337. Additionally, this work was supported by the Spanish Ministry of Science and Innovation, MINECO, under project PID2019-109269RB-C43 and FEDER program. D.L. would like to acknowledge the Independent Research Fund Denmark (Danmarks Frie Forskningsfond) under Grant agreement 1026-00420B. D.L., A.L., F.J.G.V. and F.J.P.I. would like to acknowledge financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). G.L. is supported by the Chinese Meridian Project, and the International Partnership Program of Chinese Academy of Sciences (No.183311KYSB20200003). ASIM is a mission of the European Space Agency (ESA) and is funded by ESA and by national grants of Denmark, Norway and Spain. The ASIM Science Data Centre is supported by ESA PRODEX contracts C 4000115884 (DTU) and 4000123438 (Bergen).Peer reviewe

Submicrosecond Spectroscopy of Lightning-Like Discharges: Exploring New Time Regimes

Abstract Submicrosecond (0.476 μs per frame with an exposure time of 160 ns) high-resolution (0.38 nm) time-resolved spectra of laboratory-produced lightning-like electrical discharges have been recorded for the first time within the visible spectral range (645–665 nm). The spectra were recorded with the GrAnada LIghtning Ultrafast Spectrograph (GALIUS), a high-speed imaging spectrograph recently developed for lightning research in the IAA-CSIC. Unprecedented spectral time dynamics are explored for meter long laboratory electrical discharges produced with a 2.0 MV Marx generator. The maximum electron density and gas temperature measured in a timescale of ≤0.50 μs (160 ns) were, respectively, ≃1018 cm−3 and ≃32,000 K. Overpressure in the lightning-like plasma channel, black-body dynamics, and self-absorption in spectral lines were investigated

Spectral Observations of Optical Emissions Associated With Terrestrial Gamma-Ray Flashes

The Atmosphere-Space Interactions Monitor measures Terrestrial Gamma-Ray Flashes (TGFs) simultaneously with optical emissions from associated lightning activity. We analyzed optical measurements at 180–230, 337, and 777.4 nm related to 69 TGFs observed between June 2018 and October 2019. All TGFs are associated with optical emissions and 90% of them are at the onset of a large optical pulse, suggesting that they are connected with the initiation of current surges. A model of photon delay induced by cloud scattering suggests that the sources of the optical pulses are from 0.7 ms before to 4.4 ms after the TGFs, with a median of −10 ± 80 µs, and 1–5 km below the cloud top. The pulses have rise times comparable to lightning but longer durations. Pulse amplitudes at 337 nm are ∼3 times larger than at 777.4 nm. The results support the leader-streamer mechanism for TGF generation.publishedVersio

High-resolution spectra of sprites and halos with GRASSP

The first and simultaneous spectroscopic campaigns of TLEs were carried out in the mid 1990s [1, 2], soon after the discovery of TLEs in 1989 [3]. These initial campaigns provided preliminary results on the optical emissions of TLEs corresponding to the first positive system (FPS) of N2(B3¿g) ¿ N2(A3S+u ) in the visible and near infrared (NIR) spectral range (540–840 nm) recorded at standard video rate (30 fps) and at low (between 9 and 6 nm) spectral resolution. More recently, in 2007, spectroscopic observations of sprite optical emissions between 640 nm and 820 nm pro- vided information on the relative vibrational concentrations of the emitting electronic state N2(B3¿g, v’) at differ- ent altitudes using higher video rate (300 fps) and higher spectral resolution (3 nm) spectrographs [4] originally designed for aurora spectroscopy [5]. The above mentioned sporadic TLE spectroscopic campaigns identified some of the key optical emissions from sprites (a type of TLE) and were even able to quantify some of the vibrational concentrations of the emitting levels in reasonable agreement with model predictions [6–8]. However, the best spectral resolution achieved to date is 3 nm and it is not enough to spectrally resolve the different low-lying vibro-rotational transitions of the FPS of N2. This contribution focuses on (1) the latest upgrades of the GRanada Sprite Spectrograph and Polarimeter (GRASSP), a ground-based medium-high spectral resolution spectrograph aimed at characterizing from ground the spectroscopic fingerprints of all sort of TLEs occurring in the mesosphere of the Earth and (2) the GRASSP 2015, 2016 summer-autumn TLE spectroscopic campaign in Europe when we recorded high-resolution spectra of sprite halos and columniform and carrot-like sprites. GRASSP works at 0.235 nm spectral resolution covering the spectral range between 700 nm and 800 nm. The last version of GRASSP is currently installed in Castellgalí, Barcelona (Spain), it is aimed and operated manually by the operator from the UPC group on-site or operated remotely from IAA-CSIC in Granada.Peer ReviewedPreprin

Initiation of lightning flashes simultaneously observed from space and the ground: Narrow bipolar events

We investigate the initiation of four lightning flashes detected from ground by means of the Colombia Lightning Mapping Array (Colombia-LMA) and simultaneously observed from space by the optical sensors of the Atmosphere-Space Interactions Monitor (ASIM) on board the International Space Station (ISS), the Geostationary Lightning Mapper (GLM), and the Lightning Imaging Sensor on the ISS. The initiations of the flashes are characterized by isolated and predominant optical blue pulses (337.0 nm). In three of the flashes, red emissions (777.4 nm), a dominant line of hot lightning, were not detected during their initiation. In these cases, the initiations were also accompanied by bipolar VLF/LF waveform with a narrow short duration (<40 μs) and VHF emissions with high radio frequency power (<269 kW). The detection of the blue emissions without any red luminosity supports that the fast breakdown processes at the flash initiation can be exclusively of streamer nature. The onset of the fourth flash was associated with both blue and red radiation, and with weak narrow bipolar waveform in VLF/LF and low VHF power. The flashes initiated between the midlevel negative and upper positive charge regions. This paper presents and discusses the first fast breakdown processes observed simultaneously from ground by means a Lightning Mapping Array (LMA) and from space during the onset of lightning flashes.publishedVersio

Initiation of lightning flashes simultaneously observed from space and the ground: Narrow bipolar events

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).We investigate the initiation of four lightning flashes detected from ground by means of the Colombia Lightning Mapping Array (Colombia-LMA) and simultaneously observed from space by the optical sensors of the Atmosphere-Space Interactions Monitor (ASIM) on board the International Space Station (ISS), the Geostationary Lightning Mapper (GLM), and the Lightning Imaging Sensor on the ISS. The initiations of the flashes are characterized by isolated and predominant optical blue pulses (337.0 nm). In three of the flashes, red emissions (777.4 nm), a dominant line of hot lightning, were not detected during their initiation. In these cases, the initiations were also accompanied by bipolar VLF/LF waveform with a narrow short duration (<40 μs) and VHF emissions with high radio frequency power (<269 kW). The detection of the blue emissions without any red luminosity supports that the fast breakdown processes at the flash initiation can be exclusively of streamer nature. The onset of the fourth flash was associated with both blue and red radiation, and with weak narrow bipolar waveform in VLF/LF and low VHF power. The flashes initiated between the midlevel negative and upper positive charge regions. This paper presents and discusses the first fast breakdown processes observed simultaneously from ground by means a Lightning Mapping Array (LMA) and from space during the onset of lightning flashes. © 2021 The Authors.The UPC contribution: This work was supported by research Grants ESP2013-48032-C5-3-R, ESP2015-69909-C5-5-R and ESP2017-86263-C4-2-R funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”, by the “European Union”; and Grant PID2019-109269RB-C42 funded by MCIN/AEI/ 10.13039/501100011033. The IAA contribution: This work was supported by the Spanish Ministry of Science and Innovation, Ministerio de Ciencia e Innovación (AEI) under project PID2019-109269RB-C43 and the FEDER program. FJPI acknowledges the sponsorship provided by the Federal Ministry for Education and Research of Germany through the Alexander von Humboldt Foundation. AL was supported by the European Research Council (ERC) under European Union Horizon 2020 Framework Programme/ERC Grant Agreement 681257. Authors FJGV, FJPI, and AL acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV- 2017-0709). The UV contribution: This work was supported by research grants from the Spanish Ministry of Economy and the European Regional Development Fund (FEDER): ESP2013-48032-C5-1-R, ESP2015-69909-C5-1-R and ESP2017-86263-C4-1-R. The UB (University of Bergen) would like to thank the Research Council of Norway under contracts 223252/F50 (CoE). The USP (University of Sao Paulo) contribution: This work was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)— Print Project (grant number: 88887.370081/2019-00). ASIM is a mission of The European Space Agency (ESA). The project is funded by ESA and by national grants of Denmark, Norway, and Spain. We thank Keraunos(Colombia) for the LINET data.Peer reviewe

A global database on holdover time of lightning-ignited wildfires

Holdover fires are usually associated with lightning-ignited wildfires (LIWs), which can experience a smoldering phase or go undetected for several hours, days or even weeks before being reported. Since the existence and duration of the smoldering combustion in LIWs is usually unknown, holdover time is conventionally defined as the time between the lightning event that ignited the fire and the time the fire is detected. Therefore, all LIWs have an associated holdover time, which may range from a few minutes to several days. However, we lack a comprehensive understanding of holdover times. Here, we introduce a global database on holdover times of LIWs. We have collected holdover time data from 29 different studies across the world through a literature review and datasets assembled by authors of the original studies. The database is composed of three data files (censored data, non-censored data, ancillary data) and three metadata files (description of database variables, list of references, reproducible examples). Censored data are the core of the database and consist of different frequency distributions reporting the number or relative frequency of LIWs per interval of holdover time. In addition, ancillary data provide further information to understand the methods and contexts in which the data were generated in the original studies. The first version of the database contains 42 frequency distributions of holdover time built with data on more than 152 375 LIWs from 13 countries in five continents covering a time span from 1921 to 2020. This database is the first freely available, harmonized and ready-to-use global source of holdover time data, which may be used in different ways to investigate LIWs and model the holdover phenomenon. The complete database can be downloaded at https://doi.org/10.5281/zenodo.7352172 (Moris et al., 2022)