Lightning attachment processes of three natural lightning discharges

• Published in: Journal of geophysical research. Atmospheres 2015-10, Vol.120 (20), p.10,637-10,644
• Main Authors: Wang, D., Takagi, N., Gamerota, W. R., Uman, M. A., Jordan, D. M.
• Format: Article
• Language: English
• Subjects: Attachment; Correlation; Data; Discharge; Geophysics; Grounds; Height; High speed; Imaging; Imaging techniques; Lightning; Lightning discharges; Lightning flashes; Luminosity; Meteorology; return stroke; Return strokes (lightning); Strokes; Uncertainty
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2015JD023734

Using a high‐speed optical imaging system specifically designed for observing the lightning attachment process, we have documented the attachment process for six strokes in three natural lightning flashes. All strokes initiate at a height above ground and propagate bidirectionally from that height, similar to the return strokes of artificially initiated (triggered) lightning previously reported by Wang et al. (2013, 2014). Though the data are quite limited, these natural return strokes suggest a correlation between larger peak current and greater initiation height. Initiation heights determined here span 12–60 m with a typical uncertainty of less than 10 m. The initial upward return stroke luminosity speeds range from (0.8 ± 0.2) to (2.0 ± 0.4) × 108 m/s. Two first return strokes downward luminosity speeds are assessed as (1.6 ± 0.3) × 107 m/s and (1.4 ± 0.3) × 108 m/s. One of the first return strokes appeared to be initiated with a stepping pulse discharge of its leader as an inseparable part of the return stroke. Key Points Super high time‐resolved lightning attachment process of natural lightning was reported Natural return strokes also started a height above the ground and then propagated bidirectionally The downward speeds of some first return strokes are very low