The primary feature of this phase of the 2020 West Coast Fire Season is the smoke. There are unprecedentedly huge wildfires burning, and a new front on the horrors opened a few days ago with several large wildfires in Oregon and Washington State. While the fires are threatening immediate destruction to specific cities and driving people from their homes in specific locales, the smoke cloud is 2 miles or more high, and is covering the entire West Coast way out into the Pacific Ocean with life-choking particulates.
The image at the top is from the GOES satellite on the morning of September 9, showing this massive smoke cloud. The fires contained in this area include:
- The beginning stages of the fire disaster now (September 12) unfolding in Oregon, that is threatening large cities like Eugene and Portland, and has forced evacuation of around 500,000 people.
- The August Complex fire (Mendocino area) that, after merging with the Elkhorn Fire, is rated at 750,000 acres
- The North Complex fire (Plumas and Butte counties) that is over 250,000 acres, destroyed at least 2000 structures, and killed 10 people
- The SCU Lightning Complex (Santa Clara County, 390,000 acres) and LNU Lightning Complex (Napa County, 360,000 acres) that had directly threatened the SF Bay Area but are now largely burned out
- The Creek Fire (Fresno County, 175,000 acres) just south of Yosemite National Park that roared into being over the Labor Day weekend, and has featured pyrocumulonimbus clouds sending smoke high into the atmosphere
Just the fires named are well over 2 million acres burned, but there are scores of smaller fires and I’ve seen a number in the 5 million range for the total.
You’re not alone if that word, Pyrocumulonimbus, made you say Huh? Expect these sorts of cloud to become more common, as we see larger more extreme fire events in the future. This is what it looked like in the mountains near Fresno a few days ago:
According to Wikipedia, a large enough fire event will form a flammagenitus cloud. The intense heating from the wildfire forms a convection current that results in the cloud. The cloud is capable of generating its own weather, such as sparking lightning or even spawning tornados. Any lightning could potentially spread the fire further. At the extreme end of this scale is the Pyrocumulonimbus clouds, which have the shape of cumulonimbus clouds (a.k.a. thunderhead clouds) but are energized by a fire. They are essentially rain-less thunderstorms sitting atop a gigantic fire. According to NASA the one which formed over the Creek Fire is the largest such cloud ever seen in the United States. According to a SF Chronicle report, the largest pyrocumulonimbus clouds ever recorded occurred in the last three years.
Clouds like this reach the altitudes where jet aircraft fly (35,000 feet or more) and even into the lower stratosphere. David Peterson, a meteorologist with the Naval Research Laboratory in Monterey is quoted by the SF Chronicle saying that 5-10 such clouds formed over fires in California this year.
For this and other reasons, the upper atmosphere is carrying a heavy load of smoke.
On Wednesday (September 9) the San Francisco Bay Area woke up to a strange orange-red color. The cause was smoke high in the atmosphere above an inversion layer, which filtered out the the blue and green components of sunlight, leaving just yellows and reds. At the surface the air was clean, but high in the atmosphere was a huge smoke cloud. That night the inversion layer weakened allowing the smoke to reach the ground, and since then the SF Bay Area has had life-threateningly bad air quality. This pattern is expected to stay in place until Monday when a low pressure zone moves into the area bringing in fresh air.
The National Weather Service office in the SF Bay Area posted this graphic to help explain:
The marine inversion layer has played a big role in ramping up the amount of smoke hanging over us these last few days. Here’s a quick overview of what it is and how it’s able to trap smoke before it gets a chance to mix out!NWS SF Bay Area
That was followed by this further explanation:
For effective smoke dispersion and breaking free from the feedback loop of calm to light winds due to smoke, low clouds, fog blocking solar energy for daily surface warming and sea breeze development will take large scale weather system’s circulations – a few more days or longer.NWS Bay Area
In other words, the current weather pattern is light winds and low temperatures. The temperatures are in part due to the smoke, which is limiting the amount of sunlight reaching the surface. While the low temperatures are welcome relief from the extreme heat immediately prior, it is part of what the NWS calls a feedback loop preventing the air circulation required for the smoke to “mix out” (blow elsewhere).
Taken together, this is the effect:
The dark red colors along the West Coast are from thousands of air quality monitoring devices. The dark red color indicates air quality in the unhealthy range. The recommendation in such cases is to stay indoors and limit physical exertion. This is especially true for those with cardiovascular problems.
It is common for the smoke from a wildfire to make the air unhealthy, because this smoke releases a lot of particulate matter (PM2.5 and PM10) as well as other chemicals. If that wildfire hits an urban area, the brew of chemicals released into the atmosphere changes to include everything making up the buildings and vehicles that burn.
What’s different in this case is the scope of magnitude, and the only way to witness this is to zoom out as far as we have in this map.
For example, the wildfires in the SF Bay Area are largely extinguished, but we are suffering under extremely unhealthy air as this is written. That’s because of smoke having traveled a hundred miles or more. This map shows plumes extending far into the Pacific Ocean, and even halfway across the Continental USA.
This is not just the immediate threat of bad air quality. The Wikipedia page on the physical impacts of Climate Change talks about large wildfires as “a major agent for conversion of biomass and soil organic matter to CO2“. It’s then part of a pattern of decreasing the snowpack in the mountains, increased dryness in neighboring areas, increasing the frequency and temperature of hot days, all of which further increases fire danger.
In other words, the environment on the West Coast is in a feedback loop of increasing wildfire risk and severity. While the Western USA is one of many natural wildfire zones around the planet, the frequency and intensity of these fires is beyond normal. Instead it is one example of the many forms of extreme weather and climate events that have long been predicted by climate change scientists.
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