Intracloud Flashes Research Articles

Lightning leader stepping, K changes, and other observations near an intracloud flash

[1] An intracloud lightning flash in central New Mexico began with the initiation of a negative stepped leader at an altitude of 8.2 km above sea level. As this leader propagated eastward and upward, at 9.1 km above sea level it passed about 200 m to the north of a balloon-borne, electric field-change instrument (Esonde). After the first leader stopped, a second negative stepped leader began near the point of origin of the first leader, but it propagated away from the Esonde. From the changes in the electric vectors and the locations of impulsive radio frequency sources detected by a lightning-mapping array (LMA), we conclude the following: (1) The first negative stepped leader was not preceded by any significant charge rearrangement due to positive leaders. (2) Each step of the first negative leader had both a forward-going wave and a step recoil wave that propagated simultaneously backwards away from the leader tip along the existing channel. The presence of a step recoil wave during each step leads to an explanation for the existence of stepping. (3) After the first (nearby) leader stopped, step recoil waves from the second (distant) leader may have found their way onto the channel formed by the first leader. (4) After the second leader stopped, waves carrying negative charge propagated along the channel of the first leader, producing strong K changes in the electric field at the Esonde and providing a good record of the wavefront shapes.

Possible catalytic effects of ice particles on the production of NO<sub>x</sub> by lightning discharges

Abstract. It is well known that lightning produces NOx as a result of the high temperatures in discharge channels. Since most viable proposed electrification mechanisms involve ice crystals, it is reasonable to assume that lightning discharge channels frequently pass through fields of ice particles of various kinds. We address the question of whether ice crystals may serve as catalysts for the production of NOx by lightning discharges. If so, and if the effect is large, it would need to be taken into account in estimates of global NOx production by lightning. In this theoretical study, we make a series of plausible assumptions about the temperature and concentration of reactant species in the environment of discharges and we postulate a mechanism by which ice crystals are able to adsorb nitrogen atoms. We then compare production rates between uncatalyzed and catalyzed reactions at 2000 K, 3000 K, and 4000 K, which are reasonable temperatures in lightning channels as they cool down. Ice crystal catalysis is expected to produce 2.7 times more NO than if ice crystals were not present. Catalyzed NO production rates are greater at 2000 K, whereas uncatalyzed production rates are greater at 4000 K. Thus, temperatures that favor rapid NO production without ice crystals adsorbing nitrogen atoms are unfavorable for NO production in the presence of ice crystals, and vice versa. The density of atmospheric ice crystals is much larger at 10 km where intracloud (IC) flashes peak than at 5 km where cloud to ground (CG) flashes peak, thus catalytic processes are expected to be more important for IC flashes than CG flashes, perhaps explaining a portion of the discrepancy in IC and CG production rates.

Observations of simultaneous upward lightning leaders from multiple tall structures

We present high-speed camera observations (up to 7200 images per second) and correlated electric field measurements of upward lightning leaders initiated simultaneously from multiple tall towers. Four towers spanning a horizontal distance of 2.9km and ranging in height from 121 to 191m, developed upward leaders following a nearby positive cloud-to-ground (+CG) flash on 7/16/09 UT in Rapid City, South Dakota, USA during the summer thunderstorm season. The optical and electric field observations suggest that all four upward propagating leaders were positive polarity (i.e., upward negative lightning) and initiated simultaneously approximately 2ms following the +CG return stroke. There was significant intracloud flash activity prior to the return stroke, and upward leader initiation coincided with the passage of horizontally extensive in-cloud negative breakdown following the +CG return stroke. This observation supports the idea that downward positive cloud-to-ground lightning can trigger upward negative lightning from multiple tall objects. Specifically, the triggering component is an area of horizontally propagating negative breakdown following the +CG return stroke that influences a broad area resulting in simultaneous or near-simultaneous, positive polarity upward leader initiation from multiple tall objects.

Effects of Charge Distribution in Thunderstorms on Lightning Propagation Paths in Darwin, Australia

Abstract The charge distributions in a thundercloud play an important role in the initiation and propagation of lightning discharges. To further understand the effects of charge distributions on lightning discharge, the authors conducted a very high-frequency (VHF) lightning observation campaign during the 2006/07 monsoon in Darwin, Australia, using a VHF broadband digital interferometer (DITF). A C-band polarimetric weather radar to estimate the precipitation profiles such as hydrometeor classification was operated by the Bureau of Meteorology (BOM) Research Centre. Cloud-to-ground (CG) and intracloud (IC) flashes were initiated from the outer and the inner parts of the upper side of the graupel regions, respectively. In the cases of CG flashes, the negative leaders travel first about 10 km horizontally through positive charge regions and then begin to bend toward the ground when they reach the edge of the positive charge regions where there is no graupel region underneath. In contrast, in the cases of the IC flashes the negatively charged graupel regions block the downward developments of negative leaders. It is noted that positive charge regions could facilitate the extension of the horizontal negative leader. These results may suggest that lightning flash types are closely dependent on their initiation locations and the surrounding charge distributions. The experimental results are consistent with other previous observation results and charge model simulations.

Characteristics of broadband lightning emissions associated with terrestrial gamma ray flashes

To characterize lightning processes that produce terrestrial gamma ray flashes (TGFs), we have analyzed broadband (<1 Hz to 30 kHz) lightning magnetic fields for TGFs detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) satellite in 2004-2009. The majority (96%) of 56 TGF-associated lightning signals contain single or multiple VLF impulses superposed on a slow pulse that reflects a process raising considerable negative charge within 2-6 ms. Some TGF lightning emissions also contain VLF signals that precede any appreciable slow pulse and that we term precursor sferics. The analyses of 9 TGFs related to lightning discharges with location uncertainty <100 km consistently indicate that TGFs are temporally linked to the early portion of the slow process and associated VLF impulses, and not to precursor sferics. The nearly universal presence of a slow pulse suggests that the slow process plays an important role in gamma ray production. In all cases the slow process raises negative charge with a typical mean current moment of +30 kA km. The resulting charge moment change ranges from small values below +10 C km to a maximum of +200 C km, with an average of +64 C km. The current moment waveform extracted from TGF sferics with single or multiple VLF impulses also shows that the slow process initiates shortly before the major TGF-associated fast discharge. These features are generally consistent with the TGF-lightning sequence reported by Lu et al. (2010), suggesting that the majority of RHESSI TGFs are produced during the upward negative leader progression prevalent in normal polarity intracloud flashes.

Charge transfer during intracloud lightning from a time-dependent multidipole model

[1] A time-dependent, multidipole (TDMD) model has been developed to show the charge transfer during intracloud (IC) flashes with high time and space resolution. This model combines high-speed electric field measurements from a balloon-borne instrument (Esonde) and three-dimensional lightning maps from the New Mexico Tech Lightning Mapping Array (LMA). The result is a time-varying spatial distribution of charge along lightning channels, which reveals several details about charge transfer during IC flashes. For example, a flash in 2004 initially deposited negative charge in one region and later transferred part of it to another region at a lower altitude where the negative leader was more highly branched. A flash in 2007 shows charge distributions along a main channel and two short branches; each of the three channels had different charges per unit length of channel.

Three‐dimensional charge structure of a mountain thunderstorm

Lightning charge transport is analyzed for a thunderstorm which occurred on 18 August 2004 near Langmuir Laboratory in New Mexico. The analysis employs wide band measurements of the electric field by a balloon‐borne electric field sonde or Esonde, simultaneous Lightning Mapping Array measurements of VHF pulses emitted during lightning breakdown, and Next Generation Weather Radar data. The thunderstorm was composed of two principal updrafts. In the stronger updraft the positively charged particles reached altitudes up to 14 km, and in the weaker updraft the positive particles reached 11 km altitude. The negatively charged particles generated in the updraft appeared to reach altitudes up to 10 km in the strong updraft and 8 km in the weaker updraft. Just outside the updrafts the positive and negative particles drop sharply; thereafter, they drop down at a nearly linear rate, between 1 and 2 km in altitude per 10 km in horizontal distance. Initially, as the updraft developed, most charge was transported by updraft flashes; later, after about 15 to 20 min, extensive flashes were predominant. Most cloud‐to‐ground (CG) flashes transported negative charge from outside the updraft at 6 km altitude down to ground; however, some strokes of a CG reached into a higher negative charge region closer to the updraft. Nearly 6 times as much charge was transported by intracloud (IC) flashes when compared to CG flashes. The ratio of the average charge transport for an IC flash to the average charge transport for a CG flash was 1.6, while the average generator current associated with the combined updrafts was 2.3 amperes for 40 min.

A closer examination of terrestrial gamma‐ray flash‐related lightning processes

This paper presents detailed comparisons between terrestrial gamma‐ray flashes (TGFs) detected by the RHESSI satellite and the lightning processes observed by the Los Alamos Sferic Array (LASA). It was found that all RHESSI‐detected TGFs were related to normal intracloud flashes that transported electrons upward in the cloud. Detailed temporal comparisons suggest that TGFs are more likely related to small, rather than large, lightning pulses, mostly at the level of 10−1−100 V/m when the pulses are normalized to an observation distance of 100 km. The corresponding peak current was estimated to be 3–19 kA with most of them below 10 kA, if the discharges were assumed to be individual steps in a stepped‐leader process. If the discharges were considered to be directly associated with runaway breakdown processes with a current propagation speed of c, the peak current would be 0.4–3.2 kA. Analysis of events that were close to the LASA stations showed that TGFs were most likely to occur during the initial milliseconds of IC flashes while the discharge developed vertically upward from the negative to the positive charge regions in the cloud. The heights of the TGF‐related lightning pulses were estimated to be in the range of 10.5–14.1 km along the upward development. An intense NBE with a peak current of 80 kA and a height of 16.1 km was found 2.9 ms after one TGF, and is believed to not be directly associated with the TGF but may be preconditioned by the TGF‐related discharge process.

Magneto-Ionic Process for Cloud Electrification

This paper presents a theory of cloud electrification by geomagnetic control. In the atmosphere, when ion-pairs produced by collision between cloud-particles are drifted in the W-E direction by the horizontal wind, the ions of opposite polarity get separated from each other under the influence of earth's magnetic field. Lorentz forces urge these ions to move in semi-circular trajectories at different altitudes, creating the positive bipolar charged structure of the thundercloud. The continuous charging process actuated by the magneto-ionic separation and the drift of the charged cloud-particles or snow crystals generate high electric fields in both vertical and horizontal planes within the cloud; as a result, Cloud-to-Ground (CG), Intra-Cloud (IC) both vertical and horizontal, and Cloud-to-Cloud (CC) discharges occur. The nature and frequency of these discharges are determined by the geomagnetic (CM) latitude of the place of observation. Maximum thunderstorm activity is expected to occur at intermediate CM latitude stations. During violent winter thunderstorms in the northern hemisphere, the direction of wind drift within the cloud becomes E-W; then a negative dipolar charge structure develops, with its N-region lying near the crest and the P-region near the bottom of the cloud. Leader strokes from such a negative dipolar cloud contribute positive charges to ground via CG discharges. This paper also includes explanations for the cause of occurrence of IC flashes at a level higher than the N-region in a positive dipolar cloud, and the role of the IC flash preceding the CG discharge, which neutralizes a part of the positive charge in the P-region. Consequently, an equal amount of negative charge becomes unbounded in the N-region, which actuates the CG leader stroke.

Comment on “‘Seed’ electrons from muon decay for runaway mechanism in the terrestrial gamma ray flash production,” by Gerson S. Paiva, Antonio C. Pavão, and Cristiano C. Bastos

Comment on “‘Seed’ electrons from muon decay for runaway mechanism in the terrestrial gamma ray flash production,” by Gerson S. Paiva, Antonio C. Pavão, and Cristiano C. Bastos

Production of lightning NOx and its vertical distribution calculated from three‐dimensional cloud‐scale chemical transport model simulations

A three‐dimensional (3‐D) cloud‐scale chemical transport model that includes a parameterized source of lightning NOx on the basis of observed flash rates has been used to simulate six midlatitude and subtropical thunderstorms observed during four field projects. Production per intracloud (PIC) and cloud‐to‐ground (PCG) flash is estimated by assuming various values of PIC and PCG for each storm and determining which production scenario yields NOx mixing ratios that compare most favorably with in‐cloud aircraft observations. We obtain a mean PCG value of 500 moles NO (7 kg N) per flash. The results of this analysis also suggest that on average, PIC may be nearly equal to PCG, which is contrary to the common assumption that intracloud flashes are significantly less productive of NO than are cloud‐to‐ground flashes. This study also presents vertical profiles of the mass of lightning NOx after convection based on 3‐D cloud‐scale model simulations. The results suggest that following convection, a large percentage of lightning NOx remains in the middle and upper troposphere where it originated, while only a small percentage is found near the surface. The results of this work differ from profiles calculated from 2‐D cloud‐scale model simulations with a simpler lightning parameterization that were peaked near the surface and in the upper troposphere (referred to as a “C‐shaped” profile). The new model results (a backward C‐shaped profile) suggest that chemical transport models that assume a C‐shaped vertical profile of lightning NOx mass may place too much mass near the surface and too little in the middle troposphere.

Simulated Electrification of a Small Thunderstorm with Two-Moment Bulk Microphysics

Abstract Electrification and lightning are simulated for a small continental multicell storm. The results are consistent with observations and thus provide additional understanding of the charging processes and evolution of this storm. The first six observed lightning flashes were all negative cloud-to-ground (CG) flashes, after which intracloud (IC) flashes also occurred between middle and upper levels of the storm. The model simulation reproduces the basic evolution of lightning from low and middle levels to upper levels. The observed lightning indicated an initial charge structure of at least an inverted dipole (negative charge above positive). The simulations show that noninductive charge separation higher in the storm can enhance the main negative charge sufficiently to produce negative CG flashes before upper-level IC flashes commence. The result is a “bottom-heavy” tripole charge structure with midlevel negative charge and a lower positive charge region that is more significant than the upper positive region, in contrast to the traditional tripole structure that has a less significant lower positive charge region. Additionally, the occurrence of cloud-to-ground lightning is not necessarily a result of excess net charge carried by the storm, but it is primarily caused by the local potential imbalance between the lowest charge regions. The two-moment microphysics scheme used for this study predicted mass mixing ratio and number concentration of cloud droplets, rain, ice crystals, snow, and graupel. Bulk particle density of graupel was also predicted, which allows a single category to represent a greater range of particle characteristics. (An additional hail category is available but was not needed for the present study.) The prediction of hydrometeor number concentration is particularly critical for charge separation at higher temperatures (−5° &amp;lt; T &amp;lt; −20°C) in the mixed phase region, where ice crystals are produced by rime fracturing (Hallett–Mossop process) and by splintering of freezing drops. Cloud droplet concentration prediction also affected the rates of inductive charge separation between graupel and droplets.

Estimations of charge transferred and energy released by lightning flashes

Data from ground‐based and balloon‐borne electric field meters are used in conjunction with lightning mapping array data to estimate the amount of charge transferred and energy liberated by 40 lightning flashes in four New Mexico mountain thunderstorms. Two models are developed to estimate the lightning charge transfer: point charges at the geometric center of two or more lightning charge distributions, and uniform charge distributions placed along the lightning channels. Results indicate that flashes with substantial horizontal extent, primarily intracloud (IC) flashes during the storm's mature stage, are better modeled with uniform charge distributions. Less extensive flashes, both cloud‐to‐ground (CG) and early‐stage IC flashes, are better modeled with point charges. The amount of charge transferred by 29 IC flashes ranged from ±3.9 to ±85.8 C, with an average of ±17.6 C. Mature‐stage IC flashes transfer significantly more charge, on average, than early‐stage IC flashes. The 11 CG flashes transferred negative charge to the ground; the average amount of charge lowered was −8.7 C. All but one CG flash also had substantial in‐cloud charge transfers (average ±9.3 C, maximum ±44 C) in addition to the charge moved to the ground. Individual lightning charge transfers are combined with concurrent in‐cloud potentials to estimate the electrical energy released by each flash. The IC flashes released an average of 1.6 GJ of energy per flash, while the average for CG flashes was about half as much energy per flash. Using average charge and potential values for the group of storms yields lightning energy estimates of 2 × 108 to 7 × 109 J, depending on flash type and storm stage.

On the lightning hazard warning using electrostatic field: Analysis of summer thunderstorms in Spain

This work presents an analysis of lightning warnings based on atmospheric electrostatic field measurements achieved in the city of Terrassa (northeastern Spain). Seven summer thunderstorms were analyzed. Lightning location data were obtained from two lightning detection networks that provide cloud-to-ground (CG) and intra-cloud (IC) flash information. Warning behaviour was studied on the basis of the “two area method” using both electrostatic field (EF) thresholds and polarity reversal detection. The study of the total lightning locations (CG + IC) with respect to the electric field mill (EFM) site lets investigate the possible EF threshold and EF polarity inversion values useful for warning. The probability of detection (POD) and the false alarm ratio (FAR) were evaluated in both cases obtaining slightly better results by using polarity change criteria. The paper also includes a discussion about the lead times (LTs) obtained between the trigger of a warning and a CG located in the area of concern (AOC).

Lightning and Doppler radar observations of a squall line system

A typical squall line with damaging wind and hailstones occurred on 28 April 2006 in Shandong Province, middle eastern China, and caused great economic loss. The characteristics of cloud-to-ground lightning (CG) in the squall line were studied in detail by combining the data from the ground-based CG location network, two Doppler radars and the Lightning Imaging Sensor on the TRMM satellite. Results show that positive CG flashes accounted for 54.7% of the total CG flashes. During the initial developing stage, the CG flash rate was lower than 0.5fl min − 1 and most of the CG flashes were positive. It increased significantly, up to 4.5fl min − 1, along with the rapid development of the squall line, and the percentage of positive CG was more than 75% during this period. The CG flash rate began to decrease but the percentage of negative CG flash increased gradually and exceeded that of positive CG during the mature and dissipating stages. Positive CG flashes tended to occur on the right flank and negative ones on the left flank. Strong wind at the surface occurred in or near the regions with dense positive CG flashes. Almost all positive CG flashes occurred near the strong radar echo regions, in the front parts of the squall line. However, the negative CG flashes almost exclusively occurred in the regions with weak and uniform radar echoes. The total flash rate in the storm was very high, up to 136fl min − 1, and its ratio of intracloud flashes (IC) to CG flashes was 35:1. Dense positive CG flashes corresponded to updraft regions, they did not occur in the core of the updraft, but just behind and close to the main updraft instead. The rear inflow jet, between 3 and 6 km, played an important role in the formation of the bow echo and very strong wind at surface. The CG distribution features in the squall line were obviously different from that of an ordinary MCS. The charge structure could be roughly described as an inverted charge structure.

Electrical characteristics of thunderstorms in different plateau regions of China

Abstract The electrical characteristics of thunderstorms in four plateau regions with different elevations are studied based on observations from 2002 to 2006. The thunderstorms can be divided into two categories, special-type and normal-type, in all four regions according to the polarity of the surface electric field (E-field) evolution beneath the thunderstorm during its mature stage. A negative surface E-field was observed beneath the special-type storm, and positive beneath the normal-type. The occurrence of the special-type thunderstorm was positively related to the elevation of the region, with the most frequent occurrence observed in the central Tibetan Plateau. The main charge region inside both types of thunderstorms could be represented basically by a tripole structure with the special-type being characterized by a larger-than-usual lower positive charge center (LPCC) at the base of the storm. The temperature difference between the surface and 2 m above the surface, T s − T 2m, and air humidity prior to the storm seem to be two key parameters which influence greatly the formation of the LPCC. A larger T s − T 2m and a lower air humidity might result in a thunderstorm with a large LPCC. The intracloud (IC) flashes could occur either within the upper dipole or more frequently within the lower dipole. The corresponding discharge height, obtained based on multiple-station measurements of lightning E-field changes, was located at about 3.3–5.6 km and 6.8–7.7 km above sea level (asl). The negative charge center was located at a range between 5.7 km and 7.7 km asl.

Study of the total lightning activity in a hailstorm

A thunderstorm that developed over northeastern Spain on 16 June 2006 is analyzed. This severe thunderstorm produced hailstones as large as 40 mm and had a lifetime of 3 h and 30 min. Radar cross-sections show strong vertical development with cloud echo tops reaching an altitude of 13 km. The specific characteristics of the lightning activity of this storm were: (i) a large amount (81%) of negative cloud-to-ground (−CG) flashes with very low peak currents (< 10 kA in absolute value), (ii) a very large proportion of intra-cloud (IC) flashes with an IC/CG ratio reaching about 400, (iii) a large number of “short” IC flashes (with only 1-VHF source according to SAFIR detection), (iv) a large increase of the −CG flash rate and of the CG proportion near the end of the storm. The rate of −CG flashes with a low peak current were observed to evolve similarly to the rates of IC flashes. Most of them have been assumed to be IC flashes misclassified by the Spanish Lightning Detection Network (SLDN). They have been filtered as it is usually done for misclassified +CG flashes. After this filtering, CG flash rates remained very low (< 1 min − 1 ) with +CG flashes sometimes dominant. All the particular lightning activity characteristics similar to those observed in the Severe Thunderstorm Electrification and Precipitation Study (STEPS) campaigns support the hypothesis that this thunderstorm could have had an inverted-polarity or complex charge structure. The maximum IC flash rate (67 min − 1 ) peaked 24 min before the presence of reflectivity higher than 60 dBZ. The IC activity abruptly decreased during the period when reflectivity was dramatically increasing. The time of maximum reflectivity observed by radar was consistent with the times of reported hail at the ground.

Transient currents in the global electric circuit due to cloud-to-ground and intracloud lightning

Intracloud (IC) and cloud-to-ground (CG) lightning flashes produce transient changes in the electric field ( E) above a thundercloud which drive transient currents in the global electric circuit (GEC). Using in-cloud and above-cloud E data from balloons, ground-based E data, and Lightning Mapping Array data, the above-cloud charge transfers due to lightning transients are estimated for five IC and five CG flashes from four thunderstorms that occurred above the mountains in New Mexico, USA, in 1999. For the five CG flashes (which transferred − 4 to − 13 C to the ground), the transient currents moved + 1 to + 5 C of charge upward from cloudtop toward the ionosphere, with an average transient charge transfer of about 35% of the charge transferred to ground. For the five IC flashes (which neutralized 6 to 21 C inside the cloud), the transient currents moved − 0.7 to − 3 C upward, with an average transient charge transfer of about 12% of the lightning charge. Estimates for three thunderstorms indicate that the transient currents made only a small GEC contribution compared to the quasi-stationary Wilson currents because of the offsetting effects of IC and CG flashes in these storms. However, storms with extreme characteristics, such as high flash rates or predominance of one flash type, may make a significant GEC contribution via lightning transients.

Intracloud discharge and the correlated basic charge structure of a thunderstorm in Zhongchuan, a Chinese Inland Plateau region

The intracloud (IC) discharge is closely related to the charge structure of thunderstorms. The location, charge moment and polarity of intracloud discharges have been analyzed by using the electric field changes from a 7-site network of slow antennas synchronized by GPS with 1 μs time resolution in the area of Zhongchuan in the Chinese Inland Plateau. Ten IC flashes, from a storm on August 20, 2004, have been fitted by using the non-linear least-square solution. The results show that five IC flashes occurred between the main negative charge region and the lower positive charge region and other five between the main negative charge region and the upper positive charge region during the mature stage of the thunderstorm. The centers of discharge were 3.2–5.6 km and 6.8–7.7 km above sea level. The neutralized moments were about 4.56–61.0 C km and 1.06–15.9 C km. It suggests that the charge structure related to the lightning discharge can be represented by a tripole but with a strong positive charge region in the lower part of the thunderstorm, with the lower positive charge region taking an active role in the discharge.

Evaluation of a new lightning-produced NO&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt; parameterization for cloud resolving models and its associated uncertainties

Abstract. A new parameterization of the lightning-produced NOx has been developed for cloud-resolving models. This parameterization is based on the unique characteristics of identifying which convective cells are capable of producing lightning based on a vertical velocity threshold and estimating the lightning flash rate in each convective cell from the non-precipitation and precipitation ice mass flux product. Further, the source location is filamentary instead of volumetric as in most previous parameterizations. This parameterization has been tested on the 10 July 1996 Stratospheric-Tropospheric Experiment: Radiation, Aerosols and Ozone (STERAO) storm. Comparisons of the simulated flash rate and NO mixing ratio (control experiment) with observations at different locations and stages of the storm show good agreement. An individual flash produces on average 121±41 moles of NO (7.3±2.5×1025 molecules NO) for the simulated high cloud base, high shear storm that is dominated by intra-cloud flash activity. Sensitivity tests have been performed to study the impact of the flash rate, the cloud-to-ground flash ratio, the flash length, the spatial distribution of the NO molecules, and the production rate per flash on the NO concentration and distribution. Results show a strong impact from the flash rate, the spatial placement of the lightning-NOx source and the number of moles produced per flash. On the other hand, the simulations show almost no impact from the different cloud-to-ground (CG) ratios and the lightning-NOx production rates per CG flash used as input to the model.