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Autumn Brings “Diablo Winds” and “Sundowners” to California’s Already Intense Wildfire Season

Himanshu Gupta • September 9th, 2021.

We’re bringing you exclusive content from our newsletter, The Forecast, right here on Medium. Sign up here. This story is from our feature called the Weather Corner, where we take a deep dive into weird weather around the world, from our September 23rd, 2021, newsletter.

This week marks the official autumnal equinox and start of fall in the Northern Hemisphere. In ClimateAi’s home state of California, it also means worsening winds blowing across the state which threaten to intensify an already record-breaking fire season.

The warm dry winds start blowing from the east, and push the air over the state’s mountain ranges towards the coast. They occur during the spring and fall, but they’re more dangerous in the fall when vegetation is drier and could become tinder. Known as “diablo winds” in northern California and the “Santa Anas” and “Sundowners” in the south, they’ve been known to spark massive wildfires, especially during drought conditions.

Through Sept. 19, the state has tracked 7,575 fires that have consumed 2.3 million acres — above the five-year average though less than last year’s 3.6 million acres, according to the California Department of Forestry and Fire Protection, commonly called Cal Fire. Northern California’s ongoing Dixie Fire, for instance, is the largest single fire in state history, burning down nearly 1 million acres.

Source: PBS


These fires have contributed to a scary new record set last month: Wildfires around the world pumped out more carbon dioxide than ever before. According to Gizmodo: “Forests on multiple continents went up in smoke, spewing out billions of tons of carbon dioxide, new data from the Copernicus Atmosphere Monitoring Service shows. In July, wildfires emitted nearly 1.3 gigatonnes of carbon dioxide, a record that was topped by August’s 1.4 gigatons. Between the two months, forest fires emitted an amount of carbon dioxide greater than all of India’s carbon emissions in a year.”

“What stood out as unusual were the number of fires, the size of the areas in which they were burning, their intensity, and also their persistence,” Mark Parrington, senior scientist and wildfire expert at the Copernicus Atmosphere Monitoring Service.

It’s part of a climate change feedback loop. Climate change exacerbates drought and wildfire conditions, as a result. Part of the problem is drought and high heat, which can kill trees and dry out dead grass, pine needles, and any other material on the bottom of the forest floor. This acts as kindling when a fire sweeps through a forest.

Source: World Resources Institute



Then, more intense fires burning increasingly dry vegetation consume more biomass — which releases more and increasingly, globally significant carbon emissions. Plus, forests naturally remove CO2 from the air, but that removal is obviously prevented when they’re burnt down. (Wildfires also inject soot and other aerosols into the atmosphere, with complex effects on warming and cooling.)

Agriculture in the state felt some of that heat (and smoke). Fires don’t only burn in forests — they also burn across rangelands and crops. On agricultural lands, they cause damage to orchards, crops, livestock, and farm infrastructure. Outside of the direct burning, smoke also damages crop quality, such as grapes used in wine production famous in Northern California.

Farm workers tend rows of red and green lettuce in California. Source:
Malcolm Carlaw
 on Flickr.


Even well-irrigated crops, such as fruit orchards and vineyards, can experience damage from the smoke and heat. Dryland crops, such as wheat which is grown in the California Central Valley, are particularly susceptible to fires when they are mature and being harvested at 18–24% moisture content. In addition, annual grasses, such as cheatgrass, create flashy fuel loads across rangelands.Farmers are resilient, and generations of them in the state have experienced wildfire season and have knowledge about how to suppress wildfires on crops and rangelands from previous farming generations. Some are even volunteer firefighters — critical for fighting wildfires that spark out in the rural areas.But still, the federal government owns about 45% of California, more than 45 million acres. Many fires in California fall on federally managed lands. Fire suppression techniques can be controversial — there’s a “let it burn” philosophy, to thin forests, or more of a suppression tack. They’re complicated decisions. Still, climate change heightens the stakes.Adaptation is an urgent and critical mandate for forest managers to avoid even more catastrophic losses across the state. That means considering different strategiesout-of-the box ideas, and innovative new technologies.

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