Upward Lightning Discharges Research Articles

Numerical Simulation to Evaluate the Effects of Upward Lightning Discharges on Thunderstorm Electrical Parameters

A theoretical discussion of the discharge effects of upward lightning simulated with a fine-resolution 2D thunderstorm model is performed in this paper, and the results reveal that the estimates of the total induced charge on the upward lightning discharge channels range from 0.67 to 118.8 C, and the average value is 19.0 C, while the ratio of the induced charge on the leader channels to the total opposite-polarity charge in the discharge region ranges from 5.9% to 47.3%, with an average value of 14.7%. Moreover, the average value of the space electrostatic energy consumed by upward lightning is 1.06×109 J. The above values are lower than those related to intracloud lightning discharges. The density of the deposited opposite-polarity charge is comparable in magnitude to that of the preexisting charge in the discharge area, and the deposition of these opposite-polarity charges rapidly destroys the original space potential well in the discharge area and greatly reduces the space electric field strength. In addition, these opposite-polarity charges are redistributed with the development of thunderstorms. The space charge redistribution caused by lightning discharges partly accounts for the complexity of the charge structures in a thunderstorm, and the complexity gradually decreases with the charge neutralization process.

Improved lightning model: Application to discuss the characteristics of upward lightning

A stochastic discharge parameterization scheme of upward lightning is presented and embedded into an existing fine resolution two-dimensional thundercloud electrification and lightning model. At present, our lightning model can simulate not only intra-cloud (IC) lightning and cloud-to-ground (CG) lightning but also upward lightning. By this improved model, 139 upward flashes originating from the tall structures were obtained. Out of these upward flashes, 67 cases occur without any nearby preceding lightning discharges (called self-initiated upward flashes), whereas 72 cases are triggered by the preceding lightning discharges (called nearby-lightning-triggered upward flashes). The relationship between the initiation of self-initiated upward flashes and thundercloud electrical environment parameters is discussed. The results show that the initiation of self-initiated upward flashes is related to the weighted average of the lower charge heights (H) and the average of the lower charge density (D). As D increases, the critical H increases. In addition, the reason for IC lightning or upward lightning triggering upward lightning is investigated. IC lightning discharges or upward lightning discharges neutralize the main negative charge region in the cloud and enhance the influence of the lower positive charge region on the ground electric field.

An analysis of the initiation of upward flashes from tall towers with particular reference to Gaisberg and Säntis Towers

In this paper, we present an analysis of the lightning events preceding initiation of upward lightning flashes from the Gaisberg and the Säntis Towers. It is found that the majority of upward lightning discharges from both towers are initiated without any preceding lightning activity. We show also that the results of the presented studies on the initiation of upward flashes from tall structures might be affected by the selected parameters of the study, namely the time and distance intervals used to identify the triggering events. Preceding events had the same polarity as triggered flashes in the case of the Säntis Tower and had opposite polarities in the case of the Gaisberg Tower. The effect of seasonal and temperature variations have been also analyzed.

Lightning discharges produced by wind turbines

AbstractNew observations with a 3‐D Lightning Mapping Array and high‐speed video are presented and discussed. The first set of observations shows that under certain thunderstorm conditions, wind turbine blades can produce electric discharges at regular intervals of ~3 s in relation to its rotation, over periods of time that range from a few minutes up to hours. This periodic effect has not been observed in static towers indicating that the effect of rotation is playing a critical role. The repeated discharges can occur tens of kilometers away from electrically active thunderstorm areas and may or may not precede a fully developed upward lightning discharge from the turbine. Similar to rockets used for triggering lightning, the fast movement of the blade tip plays an important role on the initiation of the discharge. The movement of the rotor blades allows the tip to “runaway” from the generated corona charge. The second observation is an uncommon upward/downward flash triggered by a wind turbine. In that flash, a negative upward leader was initiated from a wind turbine without preceding lightning activity. The flash produced a negative cloud‐to‐ground stroke several kilometers from the initiation point. The third observation corresponds to a high‐speed video record showing simultaneous upward positive leaders from a group of wind turbines triggered by a preceding intracloud flash. The fact that multiple leaders develop simultaneously indicates a poor shielding effect among them. All these observations provide some special features on the initiation of lightning by nonstatic and complex tall structures.

Measured current and close electric field changes associated with the initiation of upward lightning from a tall tower

We examine in detail the simultaneous lightning current waveforms, close electric field changes, and lightning location system data for upward lightning discharges initiated from the Gaisberg Tower (GBT) from 2005 to 2009. Out of 205 upward flashes, most of them (87% or 179/205) were initiated from the tower top without any nearby preceding lightning activity (called “self‐initiated”), whereas 26 upward flashes (13%) were initiated from the tower top with immediately preceding nearby lightning activity (called “nearby‐lightning‐triggered”), including 15 positive ground flashes, one negative ground flashes, and 10 cloud discharges. The possible reasons for self‐initiated upward flashes dominating at the GBT could be the field enhancement due to the Gaisberg Mountain above the surrounding terrain and low altitude of charge region during non‐convective season (September to March), since we note that self‐initiated lightning at the GBT occurred predominantly (79% or 142/179) during non‐convective season. On the other hand the majority (85% or 22/26) of nearby‐lightning‐triggered upward flashes at the GBT occurring during convective season (April to August) and 80 nearby‐lightning‐triggered upward flashes out of 81 upward flashes observed at the ten tall towers in Rapid City in South Dakota of USA occurring during summer seasons, could be due to the result of high altitude of charge region. The triggering flashes were detected to be within 1 and 18 km distance and the time intervals between them and upward lightning initiation are in the range of 0.3 to 90.7 ms.

High‐current lightning discharges in winter

AbstractLightning electric‐field waveforms related to power line faults in winter have been identified. Most of those waveforms appear to be associated with upward lightning discharges with absolute peak currents of over 100 kA. They are quite different from common return‐stroke waveforms, and the lightning discharges which produce these characteristic waveforms are called GC (Ground to Cloud) flashes. These high‐current lightning discharges are distributed around the coastline in different ways depending on their polarities. The spatial distributions of high‐current lightning discharges around Japan are also investigated. It is revealed that the region of Honshu Island along the coastline of the Sea of Japan belongs to the area in which the density of high‐current lightning flashes is the highest in Japan through the year. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 8–15, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20874

Lightning Electric Field Characteristics Associated With Transmission-Line Faults in Winter

In this paper, lightning electric field waveforms related to notable power transmission-line faults in winter along the coastline of the Sea of Japan were examined. Most of the waveforms of the observed electromagnetic field changes, which were more than five times as intense as an average negative return-stroke fields, are inferred to be associated with upward lightning discharges. Lightning discharges that produce such characteristic waveforms are termed ground-to-cloud flashes, and properties of the associated electric field waveforms are examined. These lightning discharges in winter distribute around the coastline of the Sea of Japan in different ways depending on their polarities.

Thunderstorms, Lightning, Sprites and Magnetospheric Whistler-Mode Radio Waves

Thunderstorms and the lightning that they produce are inherently interesting phenomena that have intrigued scientists and mankind in general for many years. The study of thunderstorms has rapidly advanced during the past century and many efforts have been made towards understanding lightning, thunderstorms and their consequences. Recent observations of optical phenomena above an active lightning discharge along with the availability of modern technology both for data collection and data analysis have renewed interest in the field of thunderstorms and their consequences in the biosphere. In this paper, we review the electrification processes of a thunderstorm, lightning processes and their association with global electric circuit and climate. The upward lightning discharge can cause sprites, elves, jets, etc. which are together called transient luminous events. Their morphological features and effects in the mesosphere are reviewed. The wide spectrum of electromagnetic waves generated during lightning discharges couple the lower atmosphere with the ionosphere/magnetosphere. Hence various features of these waves from ULF to VHF are reviewed with reference to recent results and their consequences are also briefly discussed.

High-Current Lightning Discharges in Winter

Lightning electric-field waveforms related to power line faults in winter have been identified. Most of those waveforms appear to be associated with upward lightning discharges with absolute peak currents of over 100 kA. They are quite different from common return-stroke waveforms, and the lightning discharges which produce these characteristic waveforms are called GC (Ground to Cloud) flashes. These high-current lightning discharges are distributed around the coastline in different ways depending on their polarities. The spatial distributions of high-current lightning discharges around Japan are also investigated. It is revealed that the region of Honshu Island along the coastline of the Sea of Japan belongs to the area in which the density of high-current lightning flashes is the highest in Japan through the year. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 8–15, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20874

The effect of a corona discharge on a lightning attachment

The interaction between the lightning leader and the space charge accumulated near the top of a ground object in the atmospheric electric field is considered using analytical and numerical models developed earlier to describe spark discharges in long laboratory gaps. The specific features of a nonstationary corona discharge that develops in the electric field of a thundercloud and a downward lightning leader are analyzed. Conditions for the development of an upward lightning discharge from a ground object and for the propagation of an upward-connecting leader from the object toward a downward lightning leader (the process determining the point of strike to the ground) are investigated. Possible mechanisms for the interaction of the corona space charge with an upward leader and prospects of using it to control downward lightning discharges are analyzed.