Investigating Winter Lightning in Kanazawa, Japan: Results from Triggered Experiments and Multi-Parameter Observations

This study investigates the unique characteristics of winter lightning in Kanazawa, Japan, using rocket-triggered lightning (RTL) experiments and multi-parameter observations. The campaign, conducted between December 2 and December 29, 2024, successfully triggered lightning events under controlled conditions, enabling detailed data collection. Key instrumentation included Rogowski coils for current measurements, electric field mills (EFM), corona discharge sensors, and a very high-frequency (VHF) interferometer (ITF) system for spatial and temporal signal analysis. A significant lightning event was successfully triggered on December 29, 2024, under intense precipitation conditions (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;80 ~\text{mm} / \mathrm{h}$</tex>), with peak currents reaching 5.1 kA and suggesting indications of a negative cloud-to-ground discharge associated with an upward positive leader. Detailed VHF interferometric mapping revealed that the lightning's upward propagation occurred within a constrained angular region, suggesting weak positive leader activity. The study emphasizes the significance of RTL as a method for examining the physical and electrical characteristics of winter lightning, offering valuable insights to advance lightning protection strategies and deepen the understanding of atmospheric electrical processes.