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Lightning-induced wildfires are severe natural disasters. However, because of the regionality and random nature of lightning, there is still an incomplete understanding within the scientific community regarding the characteristics of lightning that cause fires.

Through comprehensive analysis of multi-source data, researchers from the University of Science and Technology of China and the University of Information Science and Technology revealed that weaker lightning during thunderstorm development can also ignite forest fires. This finding, which has recently been published in the journal , is crucial for the early warning of lightning-induced fires and formulating disaster prevention strategies.

In this study, the researchers analyzed a severe lightning-induced fire event that took place in southwestern China on March 30, 2019, which resulted in 30 fatalities. They integrated surface meteorological data (precipitation, relative humidity, wind speed) with cloud-top brightness temperature data from the Himawari-8 satellite to reconstruct the detailed meteorological background field at the time of the fire.

Analysis revealed that ignition occurred during the development stage of the thunderstorm—not the mature stage as traditionally thought. The lightning frequency and intensity were lower in this phase, but the discharge characteristics were unique.

Through comparison with another lightning-ignited fire case that occurred in the same region in June of the same year, the study further found that negative lightning accounted for a very high proportion of fire ignitions in both cases.

"This research potentially shifts our conventional understanding of lightning-fire ignition mechanisms," explains Professor Yong Xue, corresponding author of the study. "Although lightning during the developing phase of a thunderstorm is generally weaker compared to the mature phase, it may pose a higher risk in terms of igniting combustible materials because of the distinct atmospheric conditions often present during this stage, such as low precipitation, low humidity, and strong winds."

This study not only deepens our understanding of the causes of such fires, but also provides new ideas for the prevention and control of lightning wildfires in mountainous areas globally.