It is estimated that each year there are around 16 million lightning storms around the planet. These rays are electrical discharges that jump from one cloud to another or between the cloud and the ground along a narrow and winding channel that, in a few milliseconds, conducts a brutal electrical current that raises the temperature tens of thousands of degrees, ionizes the air, produces lightning and the crack of thunder.
When the lightning strikes the vegetation, if the place contains enough fuel and the atmospheric conditions are favourable, a fire can start. It is estimated that around 10 percent of forest fires that occur are caused by lightning. But not all lightning strikes are the same, they differ from each other in discharge intensity, duration, places between which they occur, environmental conditions, etc.
The postdoctoral researcher at the IAA Francisco Javier Pérez Invernón, our guest on Talking to Scientists, and his colleagues have studied certain types of lightning known as “direct current lightning” as the main triggers for forest fires. The rays of prolonged direct current (LCC) are electrical discharges that flow for more than a few tens of milliseconds along the conductive channel through the air. The work, published in Nature Communications, analyzes the patterns of forest fires caused by lightning of this type in a context of climate change.
The study is based on observations of a set of 5,858 fires caused by lightning in the United States, based on data collected by the Geostationary Lightning Mapper (GLM) and those provided by the US Department of Agriculture. Between total fires, GLM detected that 5,254 fires were preceded by at least one prolonged direct current lightning strike during the previous 14 days in the vicinity (up to 10 km) of the ignition point.
Ray space-based measurements LCC associated with lightning strikes were used in global climate models to obtain a projection for the 2090s by applying a lightning parameterization LCC based on the strength of the updraft in thunderstorms.
Simulation results suggest an overall 41% increase in lightning rate LCC and, therefore, an increase in the fires caused by them.
The increases are greatest in South America, the west coast of North America, Central America, Australia, South and East Asia, and Europe, while regional variations are found only in northern polar forests, where the risk of fire can affect the release of soil carbon from the permafrost.
These results show that ray schemes are needed that include rays LCC to project the occurrence of forest fires caused by lightning under climate change.
I invite you to listen to Francisco Javier Pérez Invernón, postdoctoral researcher at the Institute of Astrophysics of Andalusia (IAA), Superior Council of Scientific Investigations
References:
Pérez-Invernón, FJ, Gordillo-Vázquez, FJ, Huntrieser, H. et al. Variation of lightning-triggered wildfire patterns under climate change. Nat Commun 14, 739 (2023). https://doi.org/10.1038/s41467-023-36500-5