Researchers from the School of the Environment at Washington State University, Vancouver studied dry lightning in California. This type of lightning occurs with less than 2.5 mm of rainfall and has been a cause of costly wildfire outbreaks in California. We learn more about it from Dmitri Kalashnikov, a PhD candidate at the university and the lead author of the published research.
The following transcript was created by a computer and edited by a volunteer.
Dave Miller: From the Gert Boyle Studio at OPB, this is Think Out Loud, I’m Dave Miller. Dry lightning storms, meaning bolts that hit the ground when there’s little to no rain, have caused some of the largest California wildfire outbreaks in modern history, but scientists hadn’t done a long term study looking into the weather patterns in California that cause dry lightning, connecting those storms to specific wildfires; until now. A team of researchers from across the west recently published their results in the Journal of Environmental Research and Climate. Dmitri Kalashnikov is the lead author of the study. He is a PhD candidate at Washington State University in Vancouver and he joins us now. Welcome to Think Out Loud.
Dmitri Kalashnikov: Hello, thank you for having me.
Miller: Thanks for joining us. What’s the technical definition of dry lightning?
Kalashnikov: Dry lightning is essentially a regular cloud to ground lightning, but it happens with little or no rainfall that accompanies it. And the most common definition is one tenth of an inch of rainfall or less.
Miller: Maybe this is obvious, but what makes dry lightning so likely to cause wildfires?
Kalashnikov: You nailed it. It’s essentially the fact that you have this source of fire, which is the lightning bolt striking the ground, but then not enough rainfall to put out that fire.
Miller: What were the limits of scientific knowledge about dry lightning before you and this team embarked on this new work?
Kalashnikov: Essentially people- both scientists, weather forecasters, the public- were aware of the lightning caused fire risk, the risk of wildfires being caused by lightning in California, but there hadn’t been this comprehensive long term climatology that had been done like we did. We looked at a thirty four year period spanning from 1987 to 2020, and we did this systematic study where we looked at all dry lightning occurrences in this area of Central to Northern California. And for example we found out that about half of all lightning strikes that occurred during the summertime season in this region were actually dry, about forty-six percent were dry lightning.
Miller: These are such ephemeral, almost instantaneous moments. How is there thirty-four years of data about something that if you blink literally you could miss it?
Kalashnikov: That’s a great question. Thankfully, there’s this national sensor network. It’s run by a company called Vaisala [ https://www.vaisala.com/en/products/national]. They run the US National Lightning Detection Network which is this network of ground based sensors. So they’re actually based on the ground as opposed to in space and they capture the sort of electromagnetic energy that emanates from lightning strikes, and that’s why we have this data set that goes back to the nineteen eighties of fairly precise- it’s not exact- they have like a half a kilometer which is about a quarter mile location accuracy – but you know, fairly precise over a large region, and we know what day what time and generally where these lightning strikes occurred. So what we can do in this case is take that data of lightning strikes and essentially match it up with precipitation data with how much rainfall fell in that area, where that lightning happened. And that’s how we can say, okay, these lightning strikes were dry, or not.
Miller: What could land managers or firefighters or even just homeowners do with the information that you and your team have put together? How could this be used?
Kalashnikov: That’s a great question. The hope is sort of twofold. One is that we have provided this area of Central and Northern California with basically a more detailed understanding of when and where dry lightning is likely to happen. And also, we haven’t talked about this yet, but what are the main types of weather patterns which cause dry lightning, and those different weather patterns, in which parts of this region are they more likely to increase dry lightning risk? So that’s one aspect. And the other is to look at future climate projections; lightning as you mentioned, is a very ephemeral process. It’s very small scale. And so the climate models that are in existence now cannot capture lightning. It’s just too small of a process. But what we can do and we’ve done this in this current study, which we published, we can understand the kinds of large scale weather patterns which cause dry lightning. And then we can look for those weather patterns in climate model projections. And we can say, for example, fifty years from now, the kinds of weather patterns that cause dry lightning are increasing or decreasing or whatever the case may be. But at least we have a chance of actually understanding possible future changes in lightning and fire risk.
Miller: You looked at Central and Northern California, that was the data set you had, but is it fair to assume that your findings would also shed light at least on Southern Oregon? On Southwestern Oregon?
Kalashnikov: Yes, that’s a great question. I’m glad you brought that up. Absolutely, yes. The kinds of large, widespread outbreaks of dry lightning which produce a lot of these fire impacts in California, usually, not in all cases, but usually extend into at least parts of Oregon, into Southwestern Oregon and sometimes all the way up the Cascade Mountains. For example,
the big outbreak in August of 2020 which we talked about in our study, that also extended up to the Central and Northern Cascades. In fact, the Alliance Head Fire which was ignited by lightning on the Warm Springs Indian Reservation happened from that same outbreak, which caused all of those fires in California. And of course the Alliance Head Fire sort of smoldered for about two, three weeks until the Labor Day windstorm essentially fanned it Westward and it became the Santiam Canyon Fire which burned I believe, around Detroit here, and other towns in the Santiam Canyon. So that’s one example of a recent dry lightning strike, which caused a lot of damage.
Miller: We just have 30 seconds left. But what are the big questions you still want to answer about dry lightning?
Kalashnikov: Great question. The biggest questions are broader scale across the entire Western US, and we’re going to look into this. What do these patterns and climatology of dry lightning look like across the entire Western US? Across different ecosystems?
Miller: Dmitri Kalashnikov, thanks very much.
Kalashnikov: Thank you very much.
Miller: Dmitri Kalashnikov is a Climate Scientist and a PhD Candidate at Washington State University, Vancouver, Lead Author of a new study looking into dry lightning and its connections to wildfires.
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