Initiation Process of a Winter Cloud‐to‐Ground Lightning Flash

Using a broadband (from 1 to 250 MHz) interferometer with high temporal‐spatial resolution, we have observed the lightning initiation process of a winter cloud‐to‐ground lightning in Japan with great details. We found that the lightning initiation involved with multiple fast breakdowns behaving like a series of back (downward) and forth (upward) consecutive reflections in a constrained space near the main negative charge region of the lightning. We also found that some initial negative fast breakdowns could propagate with an unusually spread manner. We suggest that fast breakdowns with either reflecting features or spread manners could efficiently utilize the electrostatic energy in a local region with strong electric field for driving subsequent streamers, and therefore may widely exist in lightning initiation processes.