Thunderstorm Conditions Research Articles

Meteorological factors associated with dry thunderstorms and simultaneous lightning-ignited wildfires: The 15 June 2022 outbreak in Catalonia

Summer heatwaves and extended dry spells create optimal meteorological conditions for occasional dry thunderstorms to produce simultaneous lightning-ignited wildfires (LIW). Concurrent ignitions put a significant burden on the firefighting's initial attack, potentially allowing incipient LIWs to escape and grow into large fires. While we can reasonably forecast lightning activity, predicting dry thunderstorm conditions and potential LIW outbreaks remains challenging. In the present study, we analyze the meteorological factors associated with a LIW outbreak that took place in Catalonia on 15 June 2022, with 22 LIW reported in three consecutive days. The fire hazard was high, but not different from past LIW episodes. ERA5-derived indices related to low-level moisture showed extreme values compared to previous studies. Atmospheric conditions with an elevated lifting condensation level coupled with the synoptic framework were set for the formation of dry thunderstorms. Radar reflectivity profiles revealed sub-cloud evaporation, and rain-gauge records corroborated the occurrence of dry lightning. In the context of global warming, we expect an increase in the frequency of LIW outbreaks in the European Mediterranean region due to an increase in lightning-ignition efficiency, which refers to the average chance of fire per lightning stroke.

Sex and age characteristics of thunderstorm asthma emergency department visits

Severe asthma has been shown to occur in the combined presence of high pollen and thunderstorm conditions, also known as ‘thunderstorm asthma.’ First studied as severe epidemic events, recent longitudinal work studied less dramatic but more frequent occurrences. We explore thunderstorm asthma-related emergency department visits in the Minneapolis-St. Paul metropolitan area and evaluated risk differences by sex and age. We define a thunderstorm asthma exposure event as the daily occurrence of 2 or more lightning strikes during high pollen periods, and use daily counts of asthma-related emergency department visits to estimate relative and absolute risk of severe asthma during thunderstorm asthma events for the full population and for sex and age subgroups. The overall population had a 1.06 (95 % CI: 1.02, 1.09) times higher risk of asthma-related ED visits during thunderstorm asthma events compared to days without thunderstorm asthma events. Children under 18 show no higher risk (RR 1.02; 95 % CI: 0.97 1.08), but adults 18–44 years (RR 1.08; 95 % CI: 1.02, 1.13) and 45 and up (RR 1.08; 95 % CI 1.02, 1.15) show higher relative risk. Absolute risk measures show similar patterns to the age and sex results, but age-sex subgroups show more variation in absolute vs relative risk. Our results support an association between ED visits and thunderstorm asthma and provide evidence of varying risks by sex across the life course. These differences in risk have implications for clinical treatment of this allergic type of asthma and for future research into this poorly recognized environmental exposure.Plain Language Summary: Recent research has highlighted the existence of Thunderstorm asthma events, a phenomenon in which pollen grains rupture in the conditions that occur with a thunderstorm, releasing sub-pollen particles that are capable of triggering severe asthma in susceptible populations. Where severe asthma is a disease that usually impacts children, we find in this study that asthma ED visits associated with thunderstorm asthma events more frequently impact adults, particularly males 18–44 and females 45 and up.

Improving lightning protection with corona minimising air terminals

A comprehensive approach to lightning protection is comprised of four key steps, namely protection against direct lightning strikes, dealing with surges and transients, dissipation of lightning currents via earthing and bonding, and protecting people. This paper deals with new research findings associated with direct-strike protection with lightning rods or “air terminals”, namely the effect of accumulated corona space charge around the tips of these components. There is now a great deal of consensus amongst lightning researchers and practitioners that space charge accumulation reduces the efficiency of an air terminal by inhibiting the initiation and development of an upward leader, a critical stage in the lightning attachment process. The paper describes measurements carried out in a high-voltage laboratory to quantify the amount of corona discharge that would be emitted under thunderstorm conditions from a variety of air terminals of different geometries. A unique, previously unreported aspect of these experiments was the corona testing of air terminals under dry and wet conditions. The results of these experiments showed that corona discharge (and hence space charge accumulation) from a standard Franklin rod is substantially higher than from the range of significantly blunter “corona minimising” air terminals that were tested. The previously reported polarity difference in corona characteristics was also observed, i.e., the magnitude of negative corona was larger than positive corona for the same ambient electric field. Differences in corona discharge were also observed under wet and dry conditions, where wet air terminals were found to produce modestly more corona. The paper then addresses the optimisation of air terminals, i.e., minimising corona discharge, for practical lightning protection applications, where the air terminal radius of curvature is tailored to its height and position of installation. Various researchers have made these calculations, the outcomes of which are summarised in this paper. In general, radii of curvature in the range 1–100 mm are required, depending on the installation height and location of the air terminal.

Basic Electrophysical Characteristics of Natural Three-Phase Dispersed System “A Storm Cloud−Earth”

The results of engineering calculation of basic electrophysical characteristics of a three-phase dispersed system of the Earth troposphere “storm cloud-earth”, in the cloud of which a bearing gaseous air phase contains fine liquid water drops and small solid dielectric particles, are present-ed. The indicated characteristics are as follows: the total electric charge qΣ concentrated in a storm cloud of a given spherical volume V0 with finely dispersed charged inclusions in the form of water droplets of the radius rw and solid dielectric particles of the radius rd with the given cor-responding average volume densities Nw and Nd, respectively; the electric potential φr in the spherical volume V0 of a storm cloud with a specified outer radius R0; the electrical energy W0 accumulated in the volume V0 of a storm cloud with finely dispersed inclusions ; and the amplitude and temporal parameters of the pulse current iL(t) of the lightning in the plasma channel of a long air spark electrical discharge from the storm cloud to the ground. It is shown that at rw ≈ rd ≈ 5 μm, Nw ≈ 108 m-3, Nd ≈ 5106 m-3, R0 ≈ 895 m and the height of the center of a spherical storm cloud (with its volume of V0 ≈ 3109 м3) H0 ≈ 3000 m above the ground level, the following numerical values (in modulus) of the sought parameters of the system under consideration could be obtained: the accumulated cloud charge of qΣ ≈ 43.8 C; the electric potential on the outer cloud surface of φR ≈ 439 MV; the electric energy of W0 ≈ 9.61 GJ; the amplitude of the lightning current of ImL ≈ 218.5 KА corresponding to the time tmL ≈ 11.1 μs. The obtained results are in a good agreement with known experimental data related to the atmospheric electricity. They will contribute to a possibility of predicting thunderstorm conditions in the Earth troposphere with the minimal initial meteorological information, the further development of the nature of the atmospheric electricity, the physics of the linear lightning and solving the problem of the lightning protection of air and ground facilities and their personnel.

Compounding Heatwave‐Extreme Rainfall Events Driven by Fronts, High Moisture, and Atmospheric Instability

AbstractHeatwaves have been shown to increase the likelihood and intensity of extreme rainfall occurring immediately afterward, potentially leading to increased flood risk. However, the exact mechanisms connecting heatwaves to extreme rainfall remain poorly understood. In this study, we use weather type data sets for Australia and Europe to identify weather patterns, including fronts, cyclones, and thunderstorm conditions, associated with heatwave terminations and following extreme rainfall events. We further analyze, using reanalysis data, how atmospheric instability and moisture availability change before and after the heatwave termination depending on whether the heatwave is followed by extreme rainfall, as well as the location of the heatwave. We find that most heatwaves terminate during thunderstorm and/or frontal conditions. Additionally, atmospheric instability and moisture availability increase several days before the heatwave termination; but only if heatwaves are followed by extreme rainfall. We also find that atmospheric instability and moisture after a heatwave are significantly higher than expected from climatology for the same time of the year, and that highest values of instability and moisture are associated with highest post‐heatwave rainfall intensities. We conclude that the joint presence of high atmospheric instability, moisture, as well as frontal systems are likely to explain why rainfall is generally more extreme and likely after heatwaves, as well as why this compound hazard is mainly found in the non‐arid mid and high latitudes. An improved understanding of the drivers of these compound events will help assess potential changing impacts in the future.

Thunderstorm environments in Europe

Abstract. Meteorological environments favorable for thunderstorms are studied across Europe, including rare thunderstorm conditions from seasons with climatologically few thunderstorms. Using cluster analysis on ERA5 reanalysis data and EUCLID (European Cooperation for Lightning Detection) lightning data, two major thunderstorm environments are found: wind-field thunderstorms, characterized by increased wind speeds, high shear, strong large-scale vertical velocities, and low CAPE values compared to other thunderstorms in the same region, and mass-field thunderstorms, characterized by large CAPE values, high dew point temperatures, and elevated isotherm heights. Wind-field thunderstorms occur mainly in winter and more over the seas, while mass-field thunderstorms occur more frequently in summer and over the European mainland. Several sub-environments of these two major thunderstorm environments exist. Principal component analysis is used to identify four topographically distinct regions in Europe that share similar thunderstorm characteristics: the Mediterranean, Alpine–central, continental, and coastal regions, respectively. Based on these results it is possible to differentiate lightning conditions in different seasons from coarse reanalysis data without a static threshold or a seasonal criterion.

Prediction of airborne pollen and sub-pollen particles for thunderstorm asthma outbreaks assessment

When exposed to convective thunderstorm conditions, pollen grains can rupture and release large numbers of allergenic sub-pollen particles (SPPs). These sub-pollen particles easily enter deep into human lungs, causing an asthmatic response named thunderstorm asthma (TA). Up to now, efforts to numerically predict the airborne SPP process and to forecast the occurrence of TAs are unsatisfactory. To overcome this problem, we have developed a physically-based pollen model (DREAM-POLL) with parameterized formation of airborne SPPs caused by convective atmospheric conditions. We ran the model over the Southern Australian grass fields for 2010 and 2016 pollen seasons when four largest decadal TA epidemics happened in Melbourne. One of these TA events (in November 2016) was the worldwide most extreme one which resulted to nine deaths and hundreds of hospital patient presentations. By executing the model on a day-by-day basis in a hindcast real-time mode we predicted SPP peaks exclusively only when the four major TA outbreaks happened, thus achieving a high forecasting success rate. The proposed modelling system can be easily implemented for other geographical domains and for different pollen types.

A new network of electric field mills at the Pierre Auger Observatory

The Pierre Auger Observatory is the largest ground-based experiment for the detection of ultra-high energy cosmic rays. In a hybrid approach, many detectors – including radio antennas – observe the extensive air showers induced by cosmic rays. As part of the AugerPrime upgrade, new antennas will be installed on each of the surface-detector stations covering a total area of around 3000 km2. This will allow us to study the mass composition of cosmic rays arriving with large inclination angles.The radio emission of air showers is heavily influenced in the presence of strong atmospheric electric fields during thunderstorm conditions. In that case measured data are difficult to interpret and therefore the atmospheric electric field over the array has to be monitored. We present the design and status of a new network of electric field mills (EFM) that will be used to take on this task. We show how we plan to perform the measurements with an absolute calibration. In addition, the electric-field data will be useful for other studies related to atmospheric electricity.

Quality control procedure for 1-minute pyranometric measurements of global and shadowband-based diffuse solar irradiance

A novel automatic filtering methodology is proposed for 1-min GHI and DIF data using surface measurements obtained at five sites located in various climate zones of Argentina. The methodology contemplates DIF information obtained through the use of a shadowband or shading ring instead of the shading ball that requires a solar tracker. Three different flags are presented for suspicious or erroneous data identified by the filters of the methodology, which respond to the weight or strictness of the corresponding filter. The methodology uses filters established in the literature and proposes new filters capable of identifying slight misalignments of the shadowband as well as measurements below a minimum threshold empirically established for heavily overcast or thunderstorm conditions. A statistical analysis based on data obtained at a high-quality reference station and the modification of a pre-existing methodology is also presented. In general terms and at all sites, it is observed that the total amount of suspicious data increases significantly as the solar zenith angle increases. Overall, the methodology is able to identify and flag 15.0–44.6% erroneous or suspicious values, depending on site. The proposed methodology is applicable at any world station where the global and diffuse irradiance components are both measured.

Defining lightning-safe structures for all socio-economic communities

Four levels of lightning-safe structures are defined based on the protection expected from various lightning injury mechanisms under thunderstorm conditions. This work, therefore, provides clarification for the long-standing issue of determining the most suitable recommendation for lightning safety in various socio-economic layers of society, especially in underprivileged communities. These globally uniform and consistent guidelines will help standard development committees, lightning safety seekers and donors of protection systems, state policy developers on disaster management, the insurance sector and industries that provide lightning protection, in determining the most appropriate lightning safety measures for a given target, based on the safety requirements, societal behaviour and affordability. Significance: Lightning safety module developers could confidently adopt the definition of safe structures provided here in their guidelines. The ambiguity on both indigenous and commercial lightning safe structures (purpose made) is cleared. Standards could specify the essential features of a structure that can be considered lightning safe.

Sex and Age Characteristics of Thunderstorm Asthma Emergency Department Visits in a Midwest Metropolitan Environment (2007-2018)

Background Severe asthma has been shown to occur in the combined presence of high pollen and thunderstorm conditions, also known as ‘thunderstorm asthma.’ Studied as severe epidemic events, recent work has explored less dramatic, but more persistent chronic occurrences. We explore thunderstorm asthma-related emergency department (ED) visits in the Minneapolis-St. Paul region and evaluate unknown risk differences by sex and age groups. Methods We define a thunderstorm asthma exposure event as daily occurrence of 2 or more lightning strikes during high pollen periods. We use daily counts of asthma-related ED visits from the Minnesota Hospital Association (2007-2018). We estimate relative and absolute risk of severe asthma during thunderstorm asthma events for the full population and sex and age subgroups. Results The overall population had a 1.055 (95% CI: 1.019, 1.093) relative risk of asthma-related ED visits during thunderstorm asthma conditions. We observe a greater relative risk on the day of the exposure for males (RR 1.07; 95% CI: 1.02, 1.12) compared to females (RR 1.04; 95% CI: 1.00, 1.09), and observed age 18-44 years and 45 and up to be most vulnerable. Children have no significant increase in ED visits during thunderstorm asthma events. Absolute risk counts show similar patterns to these age and sex results, but age-sex subgroups show more variation in absolute vs relative risk for males compared to females. Conclusions Our results support an association between ED visits and thunderstorm asthma, and provide evidence of varying risk by sex across the life course. Thunderstorm asthma shows a unique pattern where middle-aged males and older females show the greatest risk, unlike baseline asthma incidence that is greatest in male children and middle-aged females. These patterns have implications for unrecognized at-risk groups and provide clinical information for this unique asthma exposure. Keywords Climate change, thunderstorm asthma, pollen, ED visits

Contrast between continental and oceanic thunderstorms in producing red sprites and halos

The observations of transient luminous events from space-borne platform extend our exploration on the mysteries of sprite phenomenology from continental thunderstorms to oceanic thunderstorms. By combining with ground-based measurements of causative strokes for hundreds of red sprites observed by the Imager of Sprites and Upper Atmospheric Lightnings (ISUAL) during 2004–2016, there is a consensus that negative cloud-to-ground (CG) strokes spawned by oceanic thunderstorms are more readily to produce sprites. The existing ground-based observations in both Caribbean Sea and near the coast of South China, mainly due to the contributions from numerous amateurs, are generally consistent with the implications of ISUAL observations. However, the physical mechanisms that might cause the enhancement of negative CG strength in the ocean remain not completely understood. There have been analyses on several cases of oceanic thunderstorms abundant in producing negative sprites. It seems that the production of negative sprites heavily depends on the size of parent thunderstorms, and they are often generated by thunderstorm conditions that are also favorable for gigantic jets.

Computation Of Temperature Distribution On A Composite Aircraft Skin Protection Grid Due To Induced Electric Current During Flight under Thunderstorm Conditions

Computation Of Temperature Distribution On A Composite Aircraft Skin Protection Grid Due To Induced Electric Current During Flight under Thunderstorm Conditions

Computation Of Temperature Distribution On A Composite Aircraft Skin Protection Grid Due To Induced Electric Current During Flight under Thunderstorm Conditions

Computation Of Temperature Distribution On A Composite Aircraft Skin Protection Grid Due To Induced Electric Current During Flight under Thunderstorm Conditions

Determining atmospheric electric fields using MGMR3D

Cosmic-ray particles impinging on the atmosphere induce high-energy particle cascades in air, an extensive air shower (EAS), emitting coherent radio emission. This emission is affected by the presence of strong electric fields during thunderstorm conditions. To reconstruct the atmospheric electric field from the measured radio footprint of the EAS we use an analytic model for the calculation of the radio emission, MGMR3D. In this work we make an extensive comparison between the results of a microscopic model for radio emission, CoREAS, to obtain an improved parametrization for MGMR3D in the presence of atmospheric electric fields, as well as confidence intervals. The approach to extract the electric field structure is applied successfully to an event with a complicated radio footprint measured by LOFAR during thunderstorm conditions. This shows that, with the improved parametrization, MGMR3D can be used to extract the structure of the atmospheric electric field.

The Relationship between High-Presentation Asthma Days in Melbourne, Australia, and Modeled Thunderstorm Environments

Abstract Epidemic asthma events represent a significant risk to emergency services as well as the wider community. In southeastern Australia, these events occur in conjunction with relatively high amounts of grass pollen during the late spring and early summer, which may become concentrated in populated areas through atmospheric convergence caused by a number of physical mechanisms including thunderstorm outflow. Thunderstorm forecasts are therefore important for identifying epidemic asthma risk factors. However, the representation of thunderstorm environments using regional numerical weather prediction models, which are a key aspect of the construction of these forecasts, have not yet been systematically evaluated in the context of epidemic asthma events. Here, we evaluate diagnostics of thunderstorm environments from historical simulations of weather conditions in the vicinity of Melbourne, Australia, in relation to the identification of epidemic asthma cases based on hospital data from a set of controls. Skillful identification of epidemic asthma cases is achieved using a thunderstorm diagnostic that describes near-surface water vapor mixing ratio. This diagnostic is then used to gain insights on the variability of meteorological environments related to epidemic asthma in this region, including diurnal variations, long-term trends, and the relationship with large-scale climate drivers. Results suggest that there has been a long-term increase in days with high water vapor mixing ratio during the grass pollen season, with large-scale climate drivers having a limited influence on these conditions. Significance Statement We investigate the atmospheric conditions associated with epidemic thunderstorm asthma events in Melbourne, Australia, using historical model simulations of the weather. Conditions appear to be associated with high atmospheric moisture content, which relates to environments favorable for severe thunderstorms, but also potentially pollen rupturing as suggested by previous studies. These conditions are shown to be just as important as the concentration of grass pollen for a set of epidemic thunderstorm asthma events in this region. This means that weather model simulations of thunderstorm conditions can be incorporated into the forecasting process for epidemic asthma in Melbourne, Australia. We also investigate long-term variability in atmospheric conditions associated with severe thunderstorms, including relationships with the large-scale climate and long-term trends.

Computation of locations of possible stepped leader attachment points on an aircraft flying under thunderstorm conditions

In case of flight in a thunderstorm region, a lightning strike on the aircraft might occur. For better lightning protection, the locations of points on the aircraft skin where a stepped leader can be attached should be delimited. In this paper, the areas of the skin of an aircraft where a stepped leader might be attached are defined through an approach based on the fact that electrostatics and potential flow theory have the same mathematical background. This is done by computing the distribution of the electrostatic field on the metallic parts of the skin of the aircraft due to the ambient electric field. In any area of the skin, where the electric field resulting from the combination of the ambient electric field and the local electric field can ionize the air, attachment points of a stepped leader might exist. The advantage of this approach is a decreased computational time and computer memory needed, as compared to a full Computational Physics approach. The areas of the skin of a generic airliner delimited through this approach, at least qualitatively, are in agreement with photos taken under real thunderstorm conditions.

Determine three-layer atmospheric electric fields using MGMR3D

Introduction: Measuring atmospheric electric fields is a difficult task because of the volatility of thunderstorms and the lack of control over direct measurement methods such as balloons. MGMR3D is a semi-analytic code that can be used to determine the structures of atmospheric electric fields during thunderstorm conditions indirectly. However, it is required to check whether the MGMR3D results have a good agreement with those provided by the microscopic model, CoREAS, in three-layer electric field cases. Methods: Using MGMR3D and CoREAS, we compared the intensity and linear and circular polarizations of radio emissions due to extensive air showers given by the two codes. Results: This work shows that a good agreement was obtained for air showers passing through more complicated electric field structures. Conclusion: This means that one can use MGMR3D to extract details on the structures of the atmospheric electric fields in thunderclouds.

On the Induced Currents to Wind Turbines by the Earth’s Atmospheric Electric Potential: Experiments With Drones

We live in an electrified atmosphere where a potential difference of about 250 kV is established between the ground and the ionosphere. The resulting potential gradient induces electric charges on the objects immersed in the atmosphere, which are more significant in tall objects. Several works have identified interferences to sensors in wind turbine rotor blades being attributed to electrostatic charging of blades. This paper presents a novel experiment using vertical wires lifted by a drone to study the currents resulting under fair-weather atmospheric conditions. Two current components are identified, one resulting in point/corona discharge and the other related to the movement. Based on the experimental results, a model for predicting induced currents on wind turbines is proposed, and estimates for thunderstorm conditions are made. The results presented in this paper are important for designing the electromagnetic compatibility measures to ensure the reliability of multi-megawatt wind turbines with blades equipped with active control systems and higher use of sensors.

The Criterion for Infinite Positron Feedback in Dynamics of Relativistic Runaway Electron Avalanches

Relativistic runaway electron avalanches (RREA) accelerated by thunderstorm large-scale electric fields are one of the sources of atmospheric gamma radiation. In strong electric fields, RREAs can multiply by the relativistic feedback. Infinite relativistic feedback makes avalanches self-sustainable and hypothetically can cause a terrestrial gamma-ray flash (TGF). This paper introduces a kinetic approach to study the relativistic feedback caused by positrons since positron feedback dominates for the directly observed electric field strengths. With this approach, the criterion for infinite positron feedback within thunderstorms is derived. Discovered criterion allows obtaining the thunderstorm electric field parameters required for infinite positron feedback for any altitude. The possibility of derived thunderstorm conditions is discussed.