Environment + Climate

Southern California wildfires have split personalities, and both will burn more acreage by midcentury

Santa Ana fires burn with more intensity, and they do their worst in a shorter period of time than summer fires

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Sequoia Natl Forest fire
Eric Paul Zamora/The Fresno Bee via AP

Wildfire in the Sequoia National Forest.

University of California climate scientists analyzed and unraveled the personalities of Southern California’s two kinds of wildfires, and found that while the notorious Santa Ana fires cause 10 times more economic damage, both kinds of fire are expected to burn more ground by midcentury.

In a research paper published today in the journal Environmental Research Letters, scientists from UCLA, UC Irvine and UC Davis predict a future with bigger wildfires, and they examine the split-personality nature of Southern California wildfires. They describe two distinct types of wildfires, those driven by offshore Santa Ana winds that kick up in the fall and non-Santa Ana fires that result primarily from hot, dry conditions in the summer. They found that Santa Ana fires burn with more intensity, and they do their worst in a shorter period of time than summer fires; in a typical Santa Ana fire, half of the territory burned is consumed in the first day of the blaze.

Co-author Alex Hall, a UCLA professor of atmospheric and oceanic sciences and expert on climate modeling, generated the future-climate projections for the research. Feeding those projections into fire ecology models, the study’s authors found that by midcentury, the area burned by Santa Ana fires will increase by 64 percent, mainly due to drier air during Santa Ana wind events. The area burned by non-Santa Ana fires will increase by 77 percent, mainly due to an increase in temperatures. The researchers also predict that the number of structures destroyed by Santa Ana fires will increase by 20 percent, and the number of structures destroyed by non-Santa Ana fires will climb by 74 percent.

“The Santa Ana fires are much larger currently, and tend to spread into the urban-wildland interface,” said Hall, a member of UCLA’s Institute of the Environment and Sustainability. “The non-Santa-Ana fires tend to be confined to less-populated forest areas with fewer structures, but as they get bigger, they could start to intrude into the urban-wildland interface. We will become more vulnerable to those summer fires, and that’s a new way of seeing fire risk in southern California.”

The research was conducted with lead author Yufang Jin, an assistant professor of land, air and water resources at UC Davis who worked at UC Irvine when this study was conducted, and James Randerson, Chancellor’s Professor of Earth System Science at UC Irvine.

Read the full news release.

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