Pu, Y., and S. A. Cummer (2019), Needles and Lightning Leader Dynamics Imaged with 100–200 MHz Broadband VHF Interferometry, Geophysical Research Letters, 46, 13556–13563. https://doi.org/10.1029/2019GL085635
I improved a broadband VHF lightning interferometer to image detailed lightning processes inside the cloud with high spatial and time resolution. This enables the discovery of needle-to-negative leader transition and other lightning development dynamics that were not readily detectable in the past.

Pu, Y.*, & Cummer, S. A*. (2024). Continuous initial breakdown development of in‐cloud lightning flashes. Journal of Geophysical Research: Atmospheres, 129(20), e2024JD041302. https://doi.org/10.1029/2024JD041302 (Eos Editor's Highlight)

Pu, Y., & Cummer, S. A. (2024). Imaging step formation in in‐cloud lightning initial development with VHF interferometry. Geophysical Research Letters, 51(1), e2023GL107388. https://doi.org/10.1029/2023GL107388
How lightning propagates in the first few milliseconds has long been a mystery. Utilizing state-of-the-art lightning imaging with a 30-250 MHz VHF interferometer, the above two papers provide clear images of the detailed processes during initial development of in-cloud lightning flashes.

Pu, Y., N. Y. Liu and S. A. Cummer, (2022), Quantification of Electric Fields in Fast Breakdown during Lightning Initiation from VHF-UHF Power Spectra, Geophysical Research Letters, 49, e2021GL097374. https://doi.org/10.1029/2021GL097374

Pu, Y., S. A. Cummer, and N. Y. Liu (2021), VHF Radio Spectrum of a Positive Leader and Implications for Electric Fields, Geophysical Research Letters, 48, e2021GL093145. https://doi.org/10.1029/2021GL093145
In-situ measurements of lightning at precise times and locations are nearly impossible. The above two papers propose novel VHF-UHF radio spectral techniques that indirectly measure electric fields in the precise regions where lightning begins/propagates.

Pu, Y., S. A. Cummer, F. C. Lyu, M. Briggs, B. Mailyan, M. Stanbro, and O. Roberts (2019), Low Frequency Radio Pulses Produced by Terrestrial Gamma-Ray Flashes, Geophysical Research Letters, 46, 6990–6997. https://doi.org/10.1029/2019GL082743
A statistical study between TGF and lightning radio signals is conducted to study TGF-lightning connection. The connection between TGF and a low frequency slow-pulse during lightning development has been confirmed.

Pu, Y., S. A. Cummer, A. Huang, M. Briggs, B. Mailyan, and S. Lesage (2020), A Satellite-Detected Terrestrial Gamma Ray Flash Produced by a Cloud-to-Ground Lightning Leader, Geophysical Research Letters, 47, e2020GL089427. https://doi.org/10.1029/2020GL089427
Built upon the slow-pulse-TGF connection, I discovered likely a new type of reverse TGF produced by a cloud-to-ground lightning leader.

Pu, Y., Cummer, S. A., Lyu, F., Zheng, Y., Briggs, M. S., Lesage, S., et al. (2023). Unsupervised clustering and supervised machine learning for lightning classification: Application to identifying EIPs for ground-based TGF detection. Journal of Geophysical Research: Atmospheres, 128, e2022JD038369. https://doi.org/10.1029/2022JD038369
I designed a machine learning framework to distinguish various lightning radio signals. This enables large-scale ground-based TGF detection using a proxy signature named EIPs, which in turn would improve our understanding of TGF generation.

Pu, Y., X. S. Qie, R. B. Jiang, Z. L. Sun, M. Y. Liu, and H. B. Zhang (2019), Broadband Characteristics of Chaotic Pulse Trains Associated with Sequential Dart Leaders in a Rocket-Triggered Lightning Flash, Journal of Geophysical Research-Atmospheres, 124, 4074–4085. https://doi.org/10.1029/2018JD029488

Pu, Y., R. Jiang, X. Qie, M. Liu, H. Zhang, Y. Fan, and X. Wu (2017), Upward negative leaders in positive triggered lightning: Stepping and branching in the initial stage, Geophysical Research Letters, 44, 7029–7035, https://doi.org/10.1002/2017GL074228
Rocket triggered lightning is useful to study detailed lightning physics due to its known occurrence. The above two papers reveal optical and broadband radio characteristics of both upward and downward negative lightning leaders.