The Three-Dimensional Locating of VHF Broadband Lightning Interferometers

Abstract

VHF (Very High Frequency) lightning interferometers can locate and observe lightning discharges with a high time resolution. Especially the appearance of continuous interferometers makes the 2-D location of interferometers further improve in time resolution and completeness. However, there is uncertainty in the conclusion obtained by simply analyzing the 2-D locating information. Without the support of other 3-D total lightning locating networks, the 2-station interferometer becomes an option to obtain 3-D information. This paper introduces a 3-D lightning location method of a 2-station broadband interferometer, which uses the theodolite wind measurement method for reference, and gives the simulation results of the location accuracy. Finally, using the multi-baseline continuous 2-D locating method and the 3-D locating method, the locating results of one intra-cloud flash and the statistical results of the initiation heights of 61 cloud-to-ground flashes and 80 intra-cloud flashes are given. The results show that the two-station interferometer has high observation accuracy on both sides of the connection between the two sites. The locating accuracy will deteriorate as the distance between the radiation source and the two stations increases or the height decreases. The actual locating results are similar to those of the existing VHF TDOA (Time Difference of Arrival) lightning locating network.which is much higher than that of the existing TDOA locating system [29]. Although these advantages can only be fully demonstrated when the interferometer is used for azimuth-elevation 2-D direction finding, the high time resolution 2-D locating of the interferometer can be used for networking observation or in combination with another set of lightning locating system to give full play to its characteristics and describe the lightning discharge process in detail [23,30,31]. Currently, the existing lightning interferometers can be roughly divided into two types: narrow-band interferometers and wide-band interferometers, depending on the bandwidth of the received signals [6,32]. The observed performance of the two types of equipment is similar, but the broadband interferometer can record the VHF broadband radiation waveform of lightning, and can use various digital signal processing methods to optimize the locating results afterward [29,33]. Especially the continuous interferometer using high-speed Analog to Digital (A/D) data acquisition card at present has a high time resolution, a large dynamic range of signal amplitude resolution and continuous sampling recording ability, making the new interferometer able to describe the lightning discharge processes more completely [29].A single-station broadband interferometer system can only give the locating results of the radiation sources in two dimensions, with which many conclusions can be made based on the estimation. Even if the 3-D information can be estimated by combining the information provided by other synchronous observation systems [22,30,31], there is still an inconvenienc...

Broadband VHF Observations of Two Natural Positive Cloud‐to‐Ground Lightning Flashes

“…Note that the 2‐D location information from the MARCOS at Site A was used for the analysis of the characteristics of the DPLs. Then, a classical double theodolite method was utilized for 3‐D lightning location in order to estimate the initiation position and initial propagation directions (Li et al, 2017; Liu et al, 2018).…”

Lightning Mapping: Techniques, Challenges, and Opportunities

“…A single broadband ITF station can provide continuous lightning mapping in 2D, through which a synchronous multistation system can visualize the lightning progression in 3D maps [55]. The broadband lightning ITF method was developed in the field of localization and is considered a novel tool in lightning discharge investigations [2], [56], [57]. The basic idea of broadband ITF is to estimate the phase difference at various frequency components of the Fourier spectra between a pair of broadband antennas.…”

“…Ushio et al [56] used the same linear fit technique by extending the antenna system with a pair of orthogonal horizontal baselines. The two baselines allowed the lightning to be mapped in 2D (azimuth and elevation).…”

“…Akita et al [66] used a VHF digital ITF system [56] to investigate the progression of the K-processes (K-type breakdowns) of cloud flashes. The 3D localization of radiation sources was achieved by using two stations of the conventional 2D ITF and by considering the arrival times.…”

“…Description/Parameters Merits /Remarks 1 Demerits/Remarks 2 model and the fast Fourier transform approach, respectively. [66]  Two sets of ITF systems similar to that in [56] were installed in two sites separated by a 5.2 km distance.  Methodologies similar to those in [56] were applied.…”