Assessing the Role of Continuing Current in Fire-Igniting Lightning Strokes with Space-Based Measurements

Lightning is a primary driver of natural wildfires globally. In mid- and high-latitude regions, summer thunderstorms are key precursors of lightning-ignited wildfires, contributing substantially to the total burned area. While the influence of meteorological conditions and fuel availability on wildfire occurrence is relatively well understood, the role of the electrical characteristics of lightning in ignition probability remains uncertain. In particular, it is unclear whether the presence of a continuing current lasting tens to hundreds of milliseconds is essential for ignition or whether it significantly affects ignition probability compared to meteorological factors and fuel availability.

In this study, we investigate the factors that increase the probability of wildfire ignition in Contiguous United States (CONUS). We investigate the meteorological conditions during the occurrence of fire-igniting flashes, the value of fire danger indices, the presence of continuing currents detected from space by the Geostationary Lightning Mapper (GLM), and the polarity of the strokes provided by the Earth Networks Lightning Total Network (ENTLN). We found that the lightning ignition efficiency of fire-igniting strokes with continuing current is slightly higher than that of lightning without continuing current. In particular, we report that strokes with continuing currents may have a higher potential to produce wildfires than cloud-to-ground strokes without continuing currents when the conditions for fire ignition and spread are less favorable. Additionally, we find that lightning strokes with continuing currents are associated with smaller burned areas, likely due to less favorable conditions for fire spread.