Evolution of Thunderstorm Electrification and Cloud Microphysics during an Intense Convective Storm: A Multi-Instrument and Modeling Study

Thunderstorm electrification arises from complex interactions among cloud microphysics, dynamics, and charge separation processes. Lightning and surface electric-field measurements alone cannot fully resolve the three-dimensional electrical structure of convective storms. Cosmic-ray muons, owing to their high penetrating power, provide a complementary probe of electrified cloud regions. Here, we investigate an intense convective thunderstorm over southern India on 27 April 2020 using a multi-instrumental framework that combines directional muon observations from the GRAPES-3 telescope [1], surface electric-field measurements, lightning location network data, satellite observations, ERA5 reanalysis, and high-resolution WRF simulations. After correcting the muon data for atmospheric pressure and solar-induced anisotropy, we identify a transient ~0.5% decrease in muon flux from the Southeast direction during the storm's mature phase [2-3]. This directional deficit occurs concurrently with enhanced electric-field variability, peak lightning activity, and the development of a vigorous mixed-phase region conducive to non-inductive charge separation, as indicated by satellite observations and WRF simulations. The consistency in timing and direction among these independent datasets provides compelling evidence for a close linkage between thunderstorm electrification and secondary cosmic-ray particles. These results demonstrate the value of directional muon observations as an independent diagnostic of electrified thunderstorms and highlight the potential of multi-instrumental analyses for investigating storm-scale electrical processes.

References

1. PK Nayak et al., Observation of thunderstorm-induced muon events in GRAPES-3 experiment, J. Atmos. Sol.–Terr. Phys. 258 (2024) 106231.
2. P.K. Nayak et al., Thunderstorm-induced muon event on 20 March 2020: Insights from the Ooty muon telescope, INSAT-3DR, and lightning observations, Physical Review D 112 (2025) 083046
3. P.K. Nayak et al., The Ooty muon telescope reveals what climate did in 2022 summer, Ind. J. Phys. 98 (2024) 4239.