Dry Lightning Causes Most Destructive California Wildfires

October in California was the height of the state’s fire season. Because of severe droughts and other climate change-related environmental problems, California is now at risk of wildfires all through the year. New research suggests that dry lighting could be the primary cause of wildfires in California.

The first comprehensive climatology of dry lightning in central and northern California was compiled by researchers at Washington State University Vancouver. There must be less than 2.5% of rain for dry lightning to strike.

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As California’s climate continues to warm, wildfires pose an increasingly serious risk to the state. Lightning outbreaks can strike various areas and spark numerous simultaneous wildfires, says Dmitri Kalashnikov, main author of the study, in a press release. This poses a significant problem for fire control because human-caused flames typically start in a single location. “Recently, in 2020, numerous lightning-caused fires burnt about one million hectares throughout this region, and previous notable large lightning-caused wildfire outbreaks occurred in 1987 and 2008.”

Researchers tracked the frequency and duration of lightning storms and the amount of precipitation that fell each day from 1987 to 2020 using data from the National Lightning Detection Network. The climatology of dry lightning and other associated meteorological variables throughout the normal fire season (May through October) was defined by merging that data with atmospheric reanalysis.

A news release claims that central and northern California’s dry lightning was generated by precipitation in the upper atmosphere superimposed on the lower atmosphere’s hot and dry conditions. The researchers also found that dry lightning strikes are possible at any time between May and October, even in “calm lightning years.”

Researches identified four large-scale atmospheric patterns associated with the lightning outbreaks after classifying the dry lightning days. A press release claims that they all have unique weather systems in place.

According to the results, during this time period, dry lightning accounted for 46% of all lightning strikes to the ground. In the summer, dry lightning is more common at higher altitudes, whereas in the fall, it is more common at lower altitudes. Unfortunately, dry grass and other plant waste are more easily ignited during this time.

Deepti Singh, co-author of the paper, says in a press release that “understanding the meteorology of dry lightning across this region can inform forecasting of possible wildfire ignitions,” which will help “better constrain future risk of wildfire ignition in California” and “can aid fire suppression efforts,” by allowing firefighting resources to be strategically pre-positioned in at-risk areas.