Dear monsoon, please materialize
Explaining what's driving the big, scary fires consuming Colorado to the L.A. Times, Forest Service ecologist Bob Keane didn't mince words: "The reason Colorado is burning is they've had prolonged drought."
That drought can prime forests for fire is well established, and, well, kind of obvious. Parched plants and trees are easier to ignite than those full of moisture. And fire thrives across dry soils and in air lacking in humidity.
It's a vicious cycle, but it could be even more cruel than we thought, says Klaus Wolter, a meteorologist and researcher with the National Oceanic and Atmospheric Adminstration's Earth System Research Laboratory in Boulder, Colo. What if, he asks, wildfire exacerbates drought, too?
I heard Wolter pose this question during a recent webinar on New Mexico's drought outlook, and was a bit floored by it, considering I'd spent the past couple of weeks under a blanket of haze created by smoke drifting into our valley from the fires engulfing much of the rest of Colorado, and hallucinating rain that never materialized in those early morning moments between sleep and consciousness. (Seriously, this has been happening to me a lot.)
Forecasters are optimistic about a productive monsoon season in the southwest this year. New Mexico is eagerly awaiting rain as we speak. "We are seeing a circulation setting up like an early monsoon," says Wolter, with southerly flows coming into the region from Mexico. "When you have those monsoon patterns set up, it doesn't stay like that all summer. You need to milk those situations."
Wolter says he's "concerned but not convinced" that the haze and particles in the air from the spate of early fires could temper the efficiency of the monsoon patterns, causing them to produce some rain, but not the good soaking we so desperately need.
Wolter is careful to point out that he isn't personally researching this question, and as he told the Summit County Citizens Voice, this is still a "back-of-the-envelope" theory. But, he says, "I'm trying to understand what happened in 2000 and 2002, when I was making these forecasts that didn't work out." In 2002, for instance, fire season took shape much the way it has this year -- it started big and early. By the end of June, some 2.8 million acres had burned in the West, about two and a half times the previous 10-year average for that time of year. The Hayman Fire tore through Colorado that year, the largest in the state's history at 137,760 acres. Conditions looked ripe for a good rainy season. But, "when the monsoon came," says Wolter, "we were getting thunderstorms, but they were just pathetic. They did not produce." At the weather station Wolter keeps at his own home, he measured less than an inch of rain in July after the Hayman Fire, compared to the three inches he gets during a healthy monsoon. "August was not much better," he says.
There are a couple of reasons he suspects that smoke could contribute to a lackluster monsoon. Haze reduces the amount of solar radiation reaching the ground, and the surface of the earth must be heated up to initiate thunderstorms. (This is why thunderstorms typically happen in the afternoon.) "So that's the first effect," he says. "It takes longer to heat up the ground and start a thunderstorm." Secondly, he says, all the fine particles in the air could "overseed" thunderclouds that do form. Droplets coalesce around the particles, but if there's too many of them, you'll get a lot of little droplets -- drizzle instead of drenching rain.
To Wolter, the impact of wildfire haze and ash on the monsoon deserves further research: "I moved here in 1988, and we had a couple of big fires in '89 and '94. But after a month or so, it was typically over. Now, it's month after month. It seems we have changed the paradigm. It could just be a function of (decades of fire suppression) and all the biomass that's waiting to burn. It's probably helped along by these warm temperatures. There's a big concern that this (paradigm) might be the future, so we need to understand it better."
The coming weeks will be fascinating to watch, Wolter believes. "It we end up with three to five inches (in Colorado) my concern is alleviated," he says. "If we get half an inch, that might be the smoke."
Cally Carswell is HCN's assistant editor.
Photo: Thunderclouds in New Mexico, courtesy of Flickr user OakleyOriginals, licensed under Creative Commons.