Photo Credit: Wildfire smoke has an intense relationship with air quality and human health. But what about its relationship with temperature and fire severity? Photo by USDA Forest Service via Flickr Creative Commons
On Labor Day weekend, my friends and I canceled a vacation rental on the Trinity River because of the heat and smoke. It was predicted to be 112 degrees inland that weekend, and we figured we’d be crazy to subject ourselves (and our posse of toddlers) to that when we could stay on the coast and enjoy fresh air and cool temperatures. Smart, right?
Credit: Jason Barnes
Saturday morning, we made breakfast at my friend’s house and watched the temperature climb. By 10 a.m., it was over 80 degrees, and by noon, it was nearing 100 — unbelievably hot for our foggy redwood coast. And on top of the heat, it was the smokiest I’ve ever seen it here. Turns out, we hadn’t escaped the heat or the smoke.
But here’s the weird thing: the inland areas, which were predicted to be unusually hot that weekend, were actually cooler than the coast. My husband, who was working on the Eclipse Complex in the Klamath Mountains — in the heart of the projected heat wave — experienced a high in the low 80s that weekend. Meanwhile, we were grappling with almost unprecedented heat here by the ocean. To have a double-digit difference in temperature between the inland areas and the coast is the norm here, but the coast is never the hotter of the two.
The odd temperature patterns that weekend reminded me of an old paper I read years ago — something about the cooling effects of forest fire smoke, and the potential to use wildfires to better understand the potential impacts of “nuclear winter.” An odd topic, but intriguing, too.
Interestingly, in looking back at the paper, I realized that it was based on data collected in the Klamath Mountains exactly thirty years before this year’s hot, smoky Labor Day weekend. The author, Alan Robock, analyzed surface temperature data from weather stations across northern California and southern Oregon, and he found that smoke from nearby wildfires had significant cooling effects in the Klamath River canyon in September of 1987 — temperatures were more than 27 degrees below normal for an entire week and more than 9 degrees cooler than normal for most of the month. During that time, the combination of an inversion and wildfire smoke created a positive feedback loop: smoke trapped by the inversion cooled the surface air temperature, which strengthened the inversion and trapped even more smoke. Of course, the smoke did more than cool the air that month; Robock notes that it also caused severe respiratory problems for people who were living in that area, and even caused tomato plants to shrivel up and die.
Inversions are common in areas with complex topography, like the Klamath Mountains. Here’s an inversion during a prescribed burn in the Klamath River canyon (Northern California Training Exchange, 2013). Credit: Lenya Quinn-Davidson, Fire Adapted Communities Learning Network
More recent studies show other important effects of temperature inversions. Earlier this year, Becky Estes and others published a paper in Ecosphere that looked at the factors influencing fire severity in the Klamath Mountains in 2006 — a year that had moderate burning conditions and is thus representative of years when wildfires might be managed for resource benefit. Of all the weather variables they looked at, temperature inversions had the strongest influence on fire severity that year. Earlier work by Miller et al. (2012) had noted similar patterns, including more surface fire and less crowning under inversions. 1987 and 2008, two of the biggest fire years in our region in the last several decades, had lower than average fire severities thanks to widespread temperature inversions.
Collectively, these studies reveal interesting tensions between humans and fire — not just here in the Klamath Mountains, but everywhere. In some ways, the inversions and smoke are producing conditions we want to see on the ground: lower fire intensities, cooler temperatures, etc. But these can come at the cost of unlivable air quality (not to mention stunted vegetables and wine that tastes like smoke!). And this isn’t just about inversions — it’s really about us finding ways to live in the crossfire of the natural checks and balances of these systems. We know that we need more fire, and that we need to take advantage of moderate burning conditions, even if that means more smoke. We just need to find good ways to do it — that’s what fire adaptation is all about. (Also, I’d be lying if I said Robock’s thoughts on nuclear winter didn’t seem a little more relevant now than they did last time I read that paper … might be worth revisiting!)
References
Estes, B. L., Knapp, E. E., Skinner, C. N., Miller, J. D., & Preisler, H. K. (2017). Factors Influencing Fire Severity Under Moderate Burning Conditions in the Klamath Mountains, Northern California, USA. Ecosphere, 8(5).
Miller, J. D., Skinner, C. N., Safford, H. D., Knapp, E. E., & Ramirez, C. M. (2012). Trends and Causes of Severity, Size, and Number of Fires in Northwestern California, USA. Ecological Applications, 22(1), 184-203.
Robock, A. (1988). Enhancement of Surface Cooling Due to Forest Fire Smoke. Science, 242, 911-913.
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