| Autor: |
Pérez‐Invernón, Francisco J., Moris, Jose V., Gordillo‐Vázquez, Francisco J., Füllekrug, Martin, Pezzatti, Gianni Boris, Conedera, Marco, Lapierre, Jeff, Huntrieser, Heidi |
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| Zdroj: |
Journal of Geophysical Research. Atmospheres; 11/16/2023, Vol. 128 Issue 21, p1-16, 16p |
| Abstrakt: |
Lightning flashes are an important source of wildfires worldwide, contributing to the emission of trace gases to the atmosphere. Based on experiments and field observations, continuing currents in lightning have since a long time been proposed to play a significant role in the ignition of wildfires. However, simultaneous detections of optical and radio signals from fire‐igniting lightning confirming the role of continuing currents in igniting wildfires are rare. In this work, we first analyze the optical signal of the lightning‐ignited wildfires reported by the Geostationary Lightning Mapper over the Contiguous United States (CONUS) during the summer of 2018, and we then analyze the optical and the Extremely Low Frequency signal of a confirmed fire‐igniting lightning flash in the Swiss Alps. Despite data uncertainties, we found that the probability of ignition of a lightning flash with Continuing Current (CC) lasting more than 10 ms is higher than that of cloud‐to‐ground lightning in CONUS. Finally, we confirm the existence of a long CC (lasting about 400 ms) associated with a long‐lasting optical signal (lasting between 2 and 4 s) of a video‐recorded fire‐igniting lightning flash. Plain Language Summary: Lightning plays a significant role in causing natural fires. Previous studies have found that a specific type of lightning, known as continuing current lightning (CC), has a higher likelihood of igniting fires. CC lightning refers to a phenomenon where electrical charge continues to flow through the channel for extended periods of tens or hundreds of milliseconds, possibly leading to elevated vegetation temperatures. In our research, we used the optical lightning detections provided by the Geostationary Lightning Mapper to estimate the probability of wildfires associated with both normal lightning and CC lightning across the United States. To gain further insights, we employed a ground camera video and analyzed extremely low‐frequency radio signals to meticulously examine the duration of CC in a lightning strike that ignited a fire in the Alps. The findings of our study demonstrate that the probability of fire occurrence is higher when CC lightning is involved compared to typical lightning strikes. This highlights the importance of understanding the characteristics of lightning and its varying impacts on fire risk assessment. Key Points: The probability of wildfire ignition by cloud‐to‐ground lightning is larger for flashes with Continuing Current (CC)The variation of the lightning ignition efficiency of lightning with CC suggest a significant influence of other factorsThe analysis of one single lightning‐ignited fire in the Alps confirms the presence of a lightning with a long CC [ABSTRACT FROM AUTHOR] |
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