Charge Structure Of Thunderstorm Research Articles

Radar, Lightning, and Synoptic Observations for a Thunderstorm on 7 January 2012 during the CHUVA-Vale Campaign

Thunderstorms can generate intense electrical activity, hail, and result in substantial economic and human losses. The development of very short-term forecasting tools (nowcasting) is essential to provide information to alert systems in order to mobilize most efficiently the population. However, the development of nowcasting tools depends on a better understanding of the physics and microphysics of clouds and lightning formation and evolution. In this context, the objectives of this study are: (a) to describe the environmental conditions that led to a genesis of a thunderstorm that produce hail on 7 January 2012, in the Metropolitan Area of São Paulo (MASP) during the CHUVA-Vale campaign, and (b) to evaluate the thunderstorm microphysical properties and vertical structure of electrical charge. Data from different sources were used: field campaign data, such as S-band radar, and 2- and 3-dimensional lightning networks, satellite data from the Geostationary Operational Environmental Satellite-13 (GOES-13), the Meteosat Second Generation (MSG), and reanalysis of the European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA5). The thunderstorm developed in a region of low-pressure due to the presence of a near-surface inverted trough and moisture convergence, which favored convection. Convective Available Potential Energy (CAPE) of 1053.6 J kg−1 at the start of the thunderstorm indicated that strong convective energy was present. Microphysical variables such as Vertically Integrated Liquid water content (VIL) and Vertically Integrated Ice (VII) showed peaks of 140 and 130 kg m−2, respectively, before the hail reached the surface, followed by a decrease, indicating content removal from within the clouds to the ground surface. The thunderstorm charge structure evolved from a dipolar structure (with a negative center between 4 and 6 km and a positive center between 8 and 10 km) to a tripolar structure (negative center between 6 and 7.5 km) in the most intense phase. The first lightning peak (100 flashes in 5 min−1) before the hail showed that there had been a lightning jump. The maximum lightning occurred around 18:17 UTC, with approximately 350 flashes 5 min−1 with values higher than 4000 sources 500 m−1 in 5 min−1. Likewise, the vertical cross-sections indicated that the lightning occurred ahead of the thunderstorm’s displacement (maximum reflectivity), which could be useful in predicting these events.

Thundercloud structures detected and analyzed based on coherent Doppler wind lidar

Abstract. The studies of intracloud discharges may shed light on the microphysical structure of thunderclouds, as both the magnitude and the sign of charge separation due to graupel collides with ice crystals within the strong updrafts are influenced by the surrounding environment. Here, a compact all-fiber coherent Doppler wind lidar (CDWL) working at the 1.5 µm wavelength is applied for probing the dynamics and microphysics structure of thunderstorms. Thanks to the precise spectrum measurement, multi-component spectra signals of thunderstorms can be analyzed by the CDWL. The spectrum width, skewness, and Doppler velocity of CDWL is used to separate and identify the particle composition and polarity. In the experiment, the thundercloud properties are detected by the CDWL, 10.6 cm Doppler weather radar (DWR), and Advanced Geosynchronous Radiation Imager (AGRI) onboard Fengyun-4 satellites. In particular, the spectrum width and skewness of the thundercloud below the 0 ∘C isotherm are increased, and when a cloud-ground lightning occurs, there is additional graupel with a velocity greater than 5 m s−1. It indicates that this region is a melting layer, and lightning activity changes the motion characteristics of graupel, affecting the charge structure of the whole thundercloud. In general, our findings provide details on the velocity, phase, and composition of particles in the outside updraft region of the thunderstorm. The identification and analysis of graupel is particularly important. It is proved that the precise spectrum of CDWL is a promising indicator for studying the charge structure of thunderstorms.

Supercell Thunderstorm Charge Structure Variability and Influences on Spatial Lightning Flash Relationships with the Updraft

Abstract Relationships between lightning flashes and thunderstorm kinematics and microphysics are important for applications such as nowcasting of convective intensity. These relationships are influenced by cloud electrification structures and have been shown to vary in anomalously electrified thunderstorms. This study addresses transitional relationships between active charge structure and lightning flash location in the context of kinematic and microphysical updraft characteristics during the development of an anomalously electrified supercell thunderstorm in the Tennessee Valley on 10 April 2009. The initial charge structure within the updraft was characterized as an anomalous dipole in which positive charge was inferred in regions of precipitation ice (i.e., graupel and hail) and negative charge was inferred in regions of cloud ice (i.e., aggregates and ice crystals). During subsequent development of the anomalous charge structure, additional minor charge layers as well as evidence of increasing horizontal complexity were observed. Microphysical and kinematic characteristics of the charge structure also evolved to include increasing observations of negative charge in precipitation ice regions, indicating the emergence of more prominent normal charging alongside dominant anomalous charging. Simultaneously, lightning flash initiation locations were also increasingly observed in regions of faster updrafts and stronger horizontal gradients in updraft speed. It is suggested that continuous variability in charging behavior over mesogamma spatial scales influenced the evolution of lightning flash locations with respect to the updraft structure. Further work is necessary to determine how this variability may impact lightning flash relationships, including lightning flash rate, with bulk microphysical and kinematic characteristics and related applications.

Radio Interferometer Observations of an Energetic in‐Cloud Pulse Reveal Large Currents Generated by Relativistic Discharges

AbstractThe production mechanism for terrestrial gamma ray flashes (TGFs) is not entirely understood, and details of the corresponding lightning activity and thunderstorm charge structure have yet to be fully characterized. Here we examine sub‐microsecond VHF (14–88 MHz) radio interferometer observations of a 247‐kA peak‐current EIP, or energetic in‐cloud pulse, a reliable radio signature of a subset of TGFs. The EIP consisted of three high‐amplitude sferic pulses lasting ≃60 μs in total, which peaked during the second (main) pulse. The EIP occurred during a normal‐polarity intracloud lightning flash that was highly unusual, in that the initial upward negative leader was particularly fast propagating and discharged a highly concentrated region of upper‐positive storm charge. The flash was initiated by a high‐power (46 kW) narrow bipolar event (NBE), and the EIP occurred about 3 ms later after ≃3 km upward flash development. The EIP was preceded ≃200 μs by a fast 6 × 106 m/s upward negative breakdown and immediately preceded and accompanied by repeated sequences of fast (107–108 m/s) downward then upward streamer events each lasting 10 to 20 μs, which repeatedly discharged a large volume of positive charge. Although the repeated streamer sequences appeared to be a characteristic feature of the EIP and were presumably involved in initiating it, the EIP sferic evolved independently of VHF‐producing activity, supporting the idea that the sferic was produced by relativistic discharge currents. Moreover, the relativistic currents during the main sferic pulse initiated a strong NBE‐like event comparable in VHF power (115 kW) to the highest‐power NBEs.

Rocket‐triggered lightning propagation paths relative to preceding natural lightning activity and inferred cloud charge

AbstractLightning Mapping Array (LMA) data are used to compare the propagation paths of seven rocket‐triggered lightning flashes to the inferred charge structure of the thunderstorms in which they were triggered. This is the first LMA study of Florida thunderstorm charge structure. Three sequentially (within 16 min) triggered lightning flashes, whose initial stages were the subject of Hill et al. (2013), are reexamined by comparing the complete flashes to the preceding natural lightning to demonstrate that the three rocket‐triggered flashes propagated through an inferred negative charge region that decreased from about 6.8 to about 4.4 km altitude as the thunderstorm dissipated. Two other flashes were also sequentially triggered (within 9 min) in a thunderstorm that contained a convectively intense region ahead of a stratiform region, with similar observed results. Finally, two unique cases of triggered lightning flashes are presented. In the first case, the in‐cloud portion of the triggered lightning flash, after ascending to and turning horizontal at 5.3 km altitude, just above the 0°C level, was observed to very clearly resemble the geometry of the in‐cloud portion of the preceding natural lightning discharges. In the second case, a flash was triggered relatively early in the storm's lifecycle that did not turn horizontal near the 0°C level, as is usually the case for triggered lightning in dissipating storms, but ascended to nearly 7.5 km altitude before exhibiting extensive horizontal branching.

Recent advances in research of lightning meteorology

Lightning meteorology focuses on investigating the lightning activities in different types of convective weather systems and the relationship of lightning to the dynamic and microphysical processes in thunderstorms. With the development and application of advanced lightning detection and location technologies, lightning meteorology has been developed into an important interdiscipline between atmospheric electricity and meteorology. This paper mainly reviews the advances of lightning meteorology research in recent years in China from the following five aspects: 1) development of advanced lightning location technology, 2) characteristics of lightning activity in different convective systems, 3) relationship of lightning to the dynamic and microphysical processes in thunderstorms, 4) charge structure of thunderstorms, and 5) lightning data assimilation techniques and application to severe weather forecasting. In addition, some important aspects on future research of the lightning meteorology are proposed.

Lightning Observation in 3D using a Multi LF Sensor Network and Comparison with Radar Reflectivity

A 3D lightning mapper consisting of multi LF sensors has been developed to monitor the thunderstorms and charge structure of thunderstorms. We have been conducting observation campaign with the 3D lightning mapper in Kansai, Japan, from October 2012. In this paper, we show 3D source locations of cloud-to-cloud (CC) and cloud-to-ground (CG) flashes and compare with radar reflectivity estimated by a phased array radar with quite high temporal and spatial resolution. Most LF sources are located in high radar reflectivity regions, indicating that the 3D lightning mapper can monitor thunderstorms. It is found that a lightning flash with heavily branches is clearly imaged. With bi-directional leader theory that negative and positive ends of a lightning leader develop simultaneously, we estimate positive and negative charge regions in a thundercloud from LF source locations. Radar reflectivity estimated by the phased array radar support the charge structure estimated by LF source locations.

Spatial and Temporal Evolution of a Multi‐Cell Thunderstorm Charge Structure in Coastal Areas

AbstractThe spatial and temporal variations of charge structure and the relationship with intensity of radar echo of a thunderstorm over low elevation, Shandong of China, have been analyzed with the radiation sources of lightning discharge three‐dimensional mapping system. The results indicate the charge structure was typical dipolar in the convective areas. The intensity of the positive charge region increased and the height of location rose with the development of thunderstorm. The negative charge region was in the area where the intensity of radar echo was more than 40 dBz and the positive charge region was in the 40 dBz radar echo area approximately. The charge structure was also inferred to be dipolar with low charge height and weak charge intensity in stratiform areas. In the dissipation stage of thunderstorm, the charge structure was ruptured for the different dissipation levels of different parts in cloud. The positive and negative charge regions sank in front of the cloud, and the height of the positive and negative charge regions had a little change in the middle part of the cloud, whereas the negative charge region attenuated. So the charge region was four layers in convective areas during dissipation stage. The above results show that the advantage charge generation mechanism often generates dipole or tripole charge structure and does not generate multipole charge structure. This paper also analyzes a negative cloud‐ to‐ground flash discharge process. Its charge structure is the same as the thunderstorm charge structure. So the thunderstorm charge structure can be illustrated by the observations of the three‐dimensional lightning mapping system.

Progresses in the atmospheric electricity researches in China during 2006–2010

Atmospheric electricity is composed of a wide range of electric phenomena in the troposphere, stratosphere, and even lower ionosphere. Research progress on atmospheric electricity in the past 5 years in China are briefly reviewed here. This research area has been greatly expanded through rocket-triggered lightning experiments and the increased use of high spatio-temporal resolution techniques for the detection and location of lightning. The main results described in this review are summarized in the following five aspects: (1) processes and parameters inferred from rocket-triggered lightning, (2) lightning physics and effects (observations and theoretical study), (3) lightning activities associated with different thunderstorms, (4) charge structure of thunderstorms (observations and simulation), and (5) the VHF/UHF lightning location techniques and discharge channel mapping.

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.

Charge Structure and Dynamics in Thunderstorms

The electrical structure inside thunderstorm clouds and the changes with time of this structure are fundamental parameters for atmospheric electricity studies on Earth. This paper gives a review of the current state of knowledge about thunderstorm charge structure based primarily on in-cloud vertical profiles through different types of deep convective clouds, cirriform anvil clouds, and stratiform precipitation regions associated with mid-latitude mesoscale convective systems. Results on the dynamical evolution of the vertical charge structure during the early and decay stages from series of balloon soundings through small thunderstorms are described, along with recent findings regarding the importance of the charge structure in determining the current contribution of small and large thunderstorms to the Earth’s global electrical circuit.

The possible charge structure of thunderstorm and lightning discharges in northeastern verge of Qinghai–Tibetan Plateau

In the summer of 2002, a comprehensive observation on thunderstorm and natural lightning discharge was conducted in the northeastern verge of Qinghai–Tibetan Plateau (101°35′E, 37°33′N, 2650 m asl). During the experiment, field mill, and fast and slow antenna systems were employed in 6 sites synchronized by GPS with 0.4 μs time resolution. In addition, a high-speed digital camera with 1 ms resolution was used in the observation. The surface electric field for one thunderstorm and a sequence of 30 flashes in the storm revealed a tripole charge structure in the mature stage. Most of the intracloud (IC) flashes occurred in the lower part and only a few occurred in the upper part of the thunderstorm. This suggests that the charging activity in the lower part of the storm was more vigorous than in the upper part. As most of the graupels fell to the ground in the dissipating stage of the storm, the lower positive charge in the thunderstorm tripole decreased, and negative cloud-to-ground (CG) flashes overwhelmingly dominated. The lower positive charge was estimated to be located at about 1.7 km above the ground, while the main negative charge was located higher than about 2.2 km above the ground. Long-duration IC discharges occurred both before and after the return strokes of two negative CG flashes that are studied. Continuing current during the IC discharge could flow along the upward channel for hundreds of milliseconds. The stepped leader of two negative CG flashes developed downward to ground with multiple branches and more than one striking point on the ground were induced as a result. The 2-D progression velocity of stepped leader was estimated to be about 0.8–1.1×10 5 m/s.

Polarity inverted intracloud discharges and electric charge structure of thunderstorm

The three-dimensional spatial and temporal development of impulsive VHF radiation events during lightning discharges has been analyzed based on the data measured by the lightning mapping array (LMA) system with high space and time resolution. The results indicate that intracloud discharges in the thunderstorm with a normal tripole charge structure occur not only between the upper positive and middle main negative charge region, but also with inverted polarity between the lower positive and middle main negative charge region. The polarity-inverted discharge originates from the middle negative charge and propagates downward to the lower positive region, where then the discharge develops horizontally. The characteristics of the discharge are similar to that of normal intracloud discharge except the polarity opposite. The results further confirmed the existence of the lower positive charge region involved in the lightning discharge. It was also found that the inverted charge structure opposite to the normal polarity appears in some storms or at a certain stage of the storm development. In the storm with a polarity inverted charge structure, a main positive charge region is located at the middle part and a negative charge at the upper part of the storm. The intracloud discharges occurred between them are of inverted polarity, showing the existence of a polarity inverted charging mechanism in storms and the complexity of storm charge structure.

Two simultaneous charge structures in thunderstorm convection

A pair of simultaneous, horizontally displaced, thunderstorm electric field soundings are used to investigate an existing conceptual model of thunderstorm charge structure. The soundings show that two different vertical charge structures, one in the updraft and one outside the updraft, can exist at the same time inside a storm, as depicted in the existing model. The data suggest that the two charge structures can be relatively close together, since the soundings are separated by only 3 to 8 km horizontally in the convective region of the storm. Horizontal extent of the charge structures is estimated to be at least 4 km × 4 km. The differences in the two charge structures are coincident with substantial differences over this same 3 to 8 km horizontal distance in the reflectivity structure, updraft speed, and lightning activity of the convection. The nonupdraft sounding was made through the intense reflectivity core found at middle levels in the convection. Additional electric field complexity and additional charge regions were found in the nonupdraft sounding, and the lightning‐related electric field changes tended to be larger in magnitude and more numerous in that sounding than in the updraft sounding.

Polarity inverted intracloud discharges and electric charge structure of thunderstorm

Polarity inverted intracloud discharges and electric charge structure of thunderstorm

Electrical structure in thunderstorm convective regions: 3. Synthesis

In this paper, results from nearly 50 electric field soundings through convective regions of mesoscale convective systems (MCSs), isolated supercells, and isolated New Mexican mountain storms are compared and synthesized. These three types of thunderstorm convection are found to have a common, basic electrical structure. Within convective updrafts the basic charge structure has four charge regions, alternating in polarity, and the lowest is positive. Outside updrafts of convection there are typically at least six charge regions, alternating in polarity, and the lowest is again positive. Among the three storm types, there are differences in the heights and temperatures at which the basic four charge regions are found in updrafts. The height (temperature) of the center of the main negative charge region averages 6.93 km (−16°C) in MCS convective region updrafts, 9.12 km (−22°C) in supercell updrafts, and 6.05 km (−7°C) in New Mexican mountain storm updrafts. In updraft soundings through all three storm types, the center height of the main negative charge region increases with increasing average balloon ascent rate and updraft speed at a rate of about 0.3 km per 1 m s−1, with a correlation coefficient of 0.94. A schematic illustrates the basic four‐ and six‐charge structure for thunderstorm convective regions, and it is offered as an improved model for thunderstorm charge structure.

On abandoning the thunderstorm tripole‐charge paradigm

We reexamine the original, half‐century‐old, in situ measurements of Simpson and colleagues used to justify the tripole model of charge structure of a thunderstorm that became the paradigm for the charge structure of mature thunderstorms. We find that the original measurements violate the criteria of the tripole model in 49% of the cases. We also reexamine our soundings of electric field in thunderstorms and mesoscale convective systems in the same way as the original soundings were. Our soundings do not fit the tripole model in at least 86% of the storms. Even when we consider only the major features in the electric field profiles, our data show noncompliance with the tripole model in 45% of the cases. We conclude that we must abandon the paradigm of the tripole‐charge structure of thunderstorms.