Lightning Position And Tracking System Research Articles

Lightning-produced NO x budget over the Highveld region of South Africa

Measurements of lightning events recorded by a lightning position and tracking system (LPATS) were used to estimate the contribution of lightning to the nitrogen oxide (NO x ) burden over the Highveld region (taken as the 4° area, Lat. 25–29°, Lon. 27–31°) of South Africa. Lightning data collected in the year 2002, comprising a total of 2 417 074 cloud-to-ground (CG) strokes, were analyzed. Lightning strokes were grouped into flashes by considering strokes occurring within radii of 10 km and time intervals of 1 s apart as belonging to the same lightning flash. Making use of a production rate of 10×10 16 molecules of NO J −1 and an energy dissipation of 6.7×10 9 J flash −1, an emission factor of 51.2 kg NO 2 flash −1 was derived. This emission factor was employed to calculate the lightning-produced NO x (LNO x ) budget of 65 (2.8–200) kt NO 2 yr −1 over the Highveld region. Our calculated LNO x is about 9% of reported NO x emissions from coal-fired power plants over the Highveld during 2002. An annual contour plot of LNO x showed that the distribution of NO x production over the Highveld is highly non-uniform, with high concentrations of LNO x over the central Highveld. These results indicate that in evaluating NO x and tropospheric ozone chemistry over the South African Highveld both natural lightning and industrial sources of NO x need to be taken into account.

Lightning Activity over Land and Sea on the Eastern Coast of the Mediterranean

This paper presents a study of the characteristics of lightning activity during the Cyprus low winter storms over the eastern coast of the Mediterranean. The focus is on changes in the nature of thunderstorms crossing the coastline from the sea into the northern and central parts of Israel, as manifested in their electrical activity. It is based on the Lightning Position and Tracking System (LPATS) measurements of lightning ground strikes during four winter seasons between 1995 and 1999. The spatial distribution shows a maximum of lightning ground strikes over Mount Carmel, possibly due to its topographical forcing. The annual variation shows a major maximum in January with two minor peaks, one in November and another in March, which can be explained by changes in the static instability of the atmosphere throughout the rainy period. The average fraction of positive ground flashes was found to be 6% and their average peak current +41 kA. The average peak current of negative ground flashes was −27 kA. Larger frequencies of ground flashes were detected over the sea than over land during the study period. This is probably due to the large heat and humidity fluxes from the sea surface, which destabilize the colder air above and drive cloud convection. The annual distribution shows that during midwinter (December–January–February) there is higher flash density over the sea, while during autumn and spring the flash density is similar above the two regions. The diurnal variation shows that the maximum in maritime lightning activity was at 0500 LST and over land at 1300 LST. The mean peak current of positive ground flashes was higher over land and of negative ground flashes, over the sea.

Advanced Lightning Location Correction of LPATS-T by Geographical Parameters

Tokyo Electric Power Company (TEPCO) introduced the Lightning Position and Tracking System (LPATS) Version III in 1990. The system uses the time-of-arrival technique for lightning location. TEPCO had studied the operating characteristics of the system, and had confirmed its effectiveness. However, further improvement of the functions and performance was necessary from the viewpoint of utilities. TEPCO, therefore, began development of the LPATS-T in cooperation with the Global Atmospherics, Inc. and formally put the system into operation in 1996.Performance of LPATS-T at TEPCO was evaluated based on comparison with actual lightning current measurement data at transmission towers. Sixty-one lightning locations at transmission towers were detected by LPATS-T from 1996 to 2000. Location error was estimated to be about 650 m on average. TEPCO corrected the lightning locations by the geographical propaga-tion path. As a result, location error was effectively improved when the lightning wavelength was set at 2, 000 m. The precision of lightning location by LPATS-T reduced the average error from 650 m to 330 m. Also, the standard deviation was 180 m from 390 m.

Evaluation of LPATS data using VHF interferometric observations of lightning flashes during the Eulinox experiment

During the Eulinox (European Lightning Nitrogen Oxides Project) campaign, two lightning sensors were available: a Lightning Position and Tracking System (LPATS), and the ONERA VHF interferometric (ITF) mapper. We looked for the typical VHF signature of positive and negative cloud-to-ground flashes in ITF records in order to separate intra-cloud (IC) flashes from cloud-to-ground (CG) flashes during five periods from 2 days. Then we used this set of data to check the efficiency of the South Germany LPATS. We concluded that this LPATS detected nearly all the negative CG flashes, but one-fourth of LPATS negative strokes are in fact IC flashes. The ratio of misinterpretation is much smaller (15%) for multi-stroke negative CG flashes. The LPATS recorded 62% of the positive strokes, but only 43% with the right polarity, and only 25% of LPATS positive strokes actually belonged to a positive CG flash. This reliability ratio is 100% if we consider only high-intensity LPATS strokes.

Reliable protection of electronics against lightning: some practical applications

The classical lightning conductor, which must prevent fire, has to have a sufficiently small resistance. An analogous condition can be formulated for the new challenge: the protection of sensitive electronics against lightning. In this case, the so-called transfer impedance, which gives the interference voltages across a sensitive input per ampere lightning current, must be made small. The arguments for this approach are described. A theoretical description is available and practical experience has been built up over the years, also in high-voltage (HV) research and in power engineering measurements in the field. This approach was used to greatly improve the lightning protection of several installations: a marine radio station, the peripheral equipment of a nuclear power plant, and an electronic siren for a nationwide public warning system. Detailed investigations were requested by our contract partners, together with suggestions for economically acceptable improvements that could be carried out in reasonable time. Later, the correctness of the renovations had to be demonstrated. In the validation measurements, we injected currents into the installation or into relevant parts thereof. The current waveform was chosen fast enough so that inductive effects determined the current distribution. At present, lightning position and tracking system (LPATS) data on lightning strikes near the marine radio station and the nuclear power plant are available to verify the effectiveness of the protection. After our improvements no more damage was reported.

A coordinated study of a storm system over the South American continent: 1. Weather information and quasi‐DC stratospheric electric field data

This paper reports on a coordinated campaign conducted in Brazil, December 13, 1989, to study the electrical signatures associated with a large storm system over the South American continent. Inside the storm, large convective cells developed extending up to the tropopause, as revealed from meteorological balloon soundings. Quasi‐DC vertical electric field and temperature were measured by zero‐pressure balloon‐borne payload launched from Cachoeira Paulista, Brazil. The data were supported by radar and GOES satellite observations, as well as by a lightning position and tracking system (LPATS). The analysis of infrared imagery supports the general tendency for lightning strikes to be near to but not exactly under the coldest cloud tops. In turn, the radar maps located the strikes near to but outside of the most intense areas of precipitation (reflectivity levels above 40 dBz). The balloon altitude and stratospheric temperature show significant variations in association with the storm. The quasi‐DC vertical electric field remained almost during the whole flight in a reversed direction relative to the usual fair weather downward orientation with values as large as 4 V/m. A simple calculation based on a static dipole model of electrical cloud structure gives charges of some tens of coulombs. In contrast with most electric field measurements in other regions, no indication of an intensification of the vertical field in the downward fair weather orientation was observed. This fact is in agreement with past observations in the South American region and seems to be related to a particular type of storm that would occur with more frequency in this region. If so, such a difference may have an important role in the global atmospheric electrical circuit, considering that South America is believed to give a significant current contribution to the global circuit.

A coordinated study of a storm system over the South American continent: 2. Lightning‐related data

On December 13, 1989, a coordinated campaign was conducted in Brazil to study the electrical signatures associated with a large storm system over the South American continent. Balloon‐borne VLF electric field data showed more than a hundred lightning‐related stratospheric vertical electric field (sferics) signatures during approximately 6 hours. The sferic signatures were characterized by a rapid transient with peak amplitudes exceeding 7 V/m which would be expected by the removal of positive charge below followed by a slow recovery. This signature indicates that the lightning strokes experienced by the balloon were either cloud discharges or positive ground discharges. The peak amplitudes indicate that the positively charged region is of the order of tens of coulombs. The recovery curves are quite variable, reflecting the complex nature of the propagating phenomena in the atmosphere. A lightning position and tracking system (LPATS) network recorded 326 ground strokes at distances less than 100 km of the balloon. In contrast with previous observations during the summer in the northern hemisphere it was found that most lightning flashes (60%) were positive. In addition, only a small fraction of them occurred simultaneously with a balloon sferic signature, indicating that most balloon sferics were a result of cloud discharges. An analysis of wind and temperature data during the event showed that the predominance of positive ground flashes is apparently not supported by the tilted dipole hypothesis, being necessary to search for other mechanisms to explain it. Although this observation cannot be considered as usual in this region, it clearly indicates that the flash polarity should depend on many factors besides the season. These factors should be probably related to the geographical location and the meteorological environment.

Lightning Direction Finding Systems and their Developments

The detection and location of lightning by magnetic direction finding system (MDFS) and lightning position and tracking system (LPATS) are major meteorological techniques in recent years. The two systems have been critically discussed and the irrelative advantages and deficiencies are focused.Lightning is a major meteorological hazard. In addition to the protection of general public, access to real time lightning ground strike data could play a vital role in forest Are measurement, computer and communication network operation, explosives and toxic material handling, aircraft refueling and maintenance and repair of utility transmission and distribution systems. Even the nuclear plant operations may be considerably impacted by lightning [1]. Ruat et al [2] have shown the value of lightning data as a component of severe thunderstorm research. The needs for accurate location of lightning ground strikes are hence well documented.This note summarize the efforts to evaluate a new lightning location technology wi...