The smoke is fortunately suspended too far aloft (at greater than 20,000 feet) to meaningfully affect the quality of the air we’re breathing near the ground. The U.S. government’s AirNow forecast calls for good air quality (code green) through Thursday.
The same cannot be said for the Pacific Northwest and West Coast, where air quality has been among the worst anywhere in the world for several days.
But by blotting out the sun, the smoke is interfering with what would have been a picture-perfect stretch of September days. If not for the fires, the D.C. area would be in the middle of a short preview of the best autumn has to offer: sparkling blue skies, pleasant temperatures and low humidity.
Instead, we have a rusty-gray smoke layer streaking over our skies.
The current round of coast-to-coast smoke got a big boost around Labor Day, when a number of large fires exploded across the West. Many have been burning since a freak lightning barrage struck Northern California in August, but the fire crisis expanded to Oregon and Washington state in the past two weeks after a heat wave followed by a rare to record combination of dry air and strong winds.
As of late Monday, California’s fires in 2020 had burned at least 3.2 million acres, an area equivalent to the size of Connecticut. This has sent unfathomable amounts of burned material into the atmosphere. Even calling it a coast-to-coast event undersells it somewhat, as parts of the plume stretch from far west into the Pacific Ocean to the Canadian Maritimes. The plume expanded across a west-to-east band some 4,000 to 5,000 miles wide.
Some of the smoke plumes have had little precedent.
With superheated air and ash rising up to 10 miles into the sky, that breathtaking height helps ensure the smoke takes a ride on the jet stream. Once it does so, spread is only limited by wind direction aloft and smoke concentration.
Reports of thick smoke have emerged across the country.
While the smoke layer in the Mid-Atlantic is much higher than it is nearer the fires, making its impact near the ground minimal, it is nonetheless quite stout.
“Smoke coverage was about the densest, most even all-day obscuration I can remember. Gray, gray, gray!” Robert Leffler, a retired climatologist for the National Weather Service, said Monday evening in an email from Damascus, Md.
Santiago Gassó of the University of Maryland’s Earth System Science Interdisciplinary Center agreed. He is an expert in high-altitude clouds, aerosols and how they are detected.
“This event is larger than past ones,” he wrote in a Twitter direct message.
The smoke plume is exceptional in three categories, Gassó wrote: “The extent of the smoke layer over the U.S. and beyond, permanence of the smoke layer in time and the levels of pollution remaining so high for such long distances.”
Gassó also stressed that the observation tools for such smoke plumes have been fairly limited historically, with better tools coming online only over the past decade or two. It is thus difficult to make long-term comparisons.
Ryan Stauffer, an expert on air pollution at NASA, concurred. “Quantitative context is tough. Colloquially yes, this is rare,” he wrote in a Twitter direct message.
It’s also likely that daytime temperatures have been held back somewhat by the thick upper-level smoke.
Leffler pointed out that some of the best forecast data was too warm by about five degrees Monday, a point emphasized by meteorologists in other affected regions as well as by the National Weather Service office serving the D.C. area.
While human-caused climate change is a major contributor to these fires, they can paradoxically lower the temperature for those downstream of their smoky fallout. This is because the smoke layer increases the albedo, or atmosphere’s reflectivity, returning some of the sun’s incoming rays back to space.
In the near term, expect more smoke.
“Hard to say it will go away any time soon,” Stauffer wrote.
While models have significant difficulty with smoky specifics, the train of smoke continues from the West, and a nose of higher pressure aloft into the Northeast is helping to hold it in place. Heading into the weekend, a dip in the jet stream across the East should help shift the pattern around enough for some clearer days, forcing the smoke southeastward.
Longer term, the pattern more or less reverts to the present, and there is unfortunately no sign of fires ending out West.
Photos of the smoke
Andrew Freedman contributed to this report.