An improved method for broadband interferometric lightning location using wavelet transforms

Abstract

[1] The principle of VHF broadband interferometer for lightning observations is to extract the phase differences between a pair of RF signals at different frequency components, and thereafter, to compute the direction of the radiation source. However, the phase difference spectra are usually distorted by random noise, which directly affects the location accuracy and reliability. In order to suppress phase interference effectively, a phase filtering algorithm which combines circular correlation with translation-invariant denoising is proposed. Application of the algorithm to a segment of observational data shows that the proposed algorithm does a much better job in recovering the phase spectra than other techniques. Simulated data distorted by the addition of random noise are also used to illustrate the improvements of the method in resolving incident angle, which is compared with other wavelet-based thresholding techniques and the conventional Fourier transform-based cross-correlation method. Finally, this phase filtering algorithm is applied to mapping two natural lightning processes. Contrast analysis reveals that this algorithm could be utilized to retrieve well-defined paths which are not discerned by conventional method, and depict the branches more clearly and precisely.

Synchronized observations of cloud‐to‐ground lightning using VHF broadband interferometer and acoustic arrays

“…Δ φ ( f ) and Δ t could be obtain by Fourier transform by a couple of VHF radiations[ Dong et al , 2001] and cross‐correlation between acoustic signals [ Few , 1970], respectively. In order to suppress random phase interference, the phase filtering algorithm [ Qiu et al , 2009] based on translation‐ invariant wavelet denoising is employed.…”

Broadband analysis of chaotic pulse trains generated by negative cloud-to-ground lightning discharge

“…The frequency range within 30 to 300 MHz was used for lightning location, while the broadband dE/dt pulses were digitized at 1 GS/s sampling rate and 8 bit resolution. The detail configuration of the broadband interferometer system is similar to that described by Dong et al [2001] and Qiu et al [2009]. Measurement site A was located in the observation field at 113.62°E, 23.57°N (the same location as described in section 2.1), while site B was located in our artificial triggered lightning experiment field (113.60°E, 23.64°N), where was about 8.15 km straightaway distance to site A (northwest).…”

Imaging lightning intracloud initial stepped leaders by low‐frequency interferometric lightning mapping array

“…In the past several decades, the main features of intracloud (IC) flashes and the incloud processes during cloud-to-ground (CG) flashes were resolved by the development of radio-based lightning mapping arrays operating at either high frequency/very high frequency (HF/VHF) [e.g., Proctor, 1981;Proctor et al, 1988;Mazur, 1989;Rhodes et al, 1994;Shao and Krehbiel, 1996;Rison et al, 1999;Kawasaki et al, 2000;Dong et al, 2002;Qiu et al, 2009;Zhang et al, 2010;Liu et al, 2012;Stock et al, 2014;Sun et al, 2014] or low frequency (LF) [e.g., Betz et al, 2004;Marshall et al, 2013;Bitzer et al, 2013;Karunarathne et al, 2013;Lyu et al, 2014;Yoshida et al, 2014;Wu et al, 2015;Wang et al, 2016]. A normal positive IC flash often starts with an initial negative leader that creates an upward channel bridging the negative and positive charge layers then horizontally extends into the two layers.…”