Dust, smoke and North America’s sunsets


Don Spain in Hillview, Kentucky, wrote on August 13, 2018: “Sunset tonight. No filters were used for this image. It been years since I have seen the sun this colorful. I wonder if the smoke from the California wildfires is reaching here.” Answer … yes.

Smoke from wildfires burning in the U.S. and Canadian West this summer has spread thousands of miles, across much of North America, manifesting as hazy skies and vivid sunsets. Plus, this week, along the U.S. Gulf Coast, we’ve also had a return of African dust. And our U.S. wildfire smoke is now heading eastward, across the Atlantic, toward Europe. I asked Les Cowley of the great website Atmospheric Optics if his site has an entry on unusual sunsets caused by wildfire smoke. I thought it might, being the world’s go-to source for all sky optics questions, ranging, literally, from anticrepuscular rays seen from aircraft to white rainbows (fogbows). Les answered:

I don’t have anything on my site about sunsets that appear affected by the smoke from the forest fires. I suppose that until the last decade or so it was not that frequent near populated areas.

As witnessed in the U.S. and other parts of the world in recent years, wildfires are increasing in frequency and severity. At Time.com, Andy Edman, chief of the science technology infusion division at the National Weather Service, explained that:

… particles of smoke that come from the fires can stay in the air and move through the Earth’s atmosphere — all the way [from western North America] to the East Coast. The smoke sits more than a mile above the Earth’s surface, but can move down through strong winds called jet streams and have an impact on air quality.

And speaking of jet streams, here is Wednesday’s Hazard Mapping System Fire and Smoke analysis from the National Oceanic and Atmospheric Administration. Notice that the smoke is heading eastward, out to sea:

August 15, 2018, analysis from NOAA. Read more about this image. It might look as if the U.S. Gulf coast has a reprieve from hazy skies, but not so. We have African dust.

Of course, North America’s west coast – where fires are raging most severely now – is experiencing North America’s smokiest skies. Some western cities – for example, Portland, Oregon – are issuing alerts on air quality. The air in western North America has been heavy with smoke this summer, and I personally know that’s a problem; I got month-long bronchitis a few summers ago after camping in Colorado under skies laden with wildfire smoke.

On the up side, Les said, this is a great opportunity to look for blue moons and suns. They’re not to be confused with the sorts of Blue Moons that aren’t related to color, but which are Blue Moons in name only. There are, indeed, also actual blue-colored moons and or blue-colored suns that can be seen when wildfire smoke fills the air, if, as Les explained:

… the smoke particles are in a narrow size range of one to a few microns across. Then they scatter light in a way that filters out red and green to leave a truly blue moon or sun.

Needless to say, blue-colored moons and suns are rare.

So, if you’re in North America, watch your sunrises and sunsets. You might see the stratified color layers like those shown in the photos on this page, caused, Les said, by larger smoke particles. Or, if the smoke particles are smaller, you might even see blue-colored moons or suns!

Read more: The year the sun turned blue

Suzanne Murphy submitted this image, reporting that, “Wildfire smoke has reached Wisconsin – setting sun, August 13, 2018.”

Wildfire sunset from Kelli Brown in Tillamook, Oregon, August 2018.

Bottom line: If you’re in North America, or even the U.K. or Europe toward the end of this week, watch your sunsets and sunrises. They might look unusual due to smoke from the raging wildfires in western North America.



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Don Spain in Hillview, Kentucky, wrote on August 13, 2018: “Sunset tonight. No filters were used for this image. It been years since I have seen the sun this colorful. I wonder if the smoke from the California wildfires is reaching here.” Answer … yes.

Smoke from wildfires burning in the U.S. and Canadian West this summer has spread thousands of miles, across much of North America, manifesting as hazy skies and vivid sunsets. Plus, this week, along the U.S. Gulf Coast, we’ve also had a return of African dust. And our U.S. wildfire smoke is now heading eastward, across the Atlantic, toward Europe. I asked Les Cowley of the great website Atmospheric Optics if his site has an entry on unusual sunsets caused by wildfire smoke. I thought it might, being the world’s go-to source for all sky optics questions, ranging, literally, from anticrepuscular rays seen from aircraft to white rainbows (fogbows). Les answered:

I don’t have anything on my site about sunsets that appear affected by the smoke from the forest fires. I suppose that until the last decade or so it was not that frequent near populated areas.

As witnessed in the U.S. and other parts of the world in recent years, wildfires are increasing in frequency and severity. At Time.com, Andy Edman, chief of the science technology infusion division at the National Weather Service, explained that:

… particles of smoke that come from the fires can stay in the air and move through the Earth’s atmosphere — all the way [from western North America] to the East Coast. The smoke sits more than a mile above the Earth’s surface, but can move down through strong winds called jet streams and have an impact on air quality.

And speaking of jet streams, here is Wednesday’s Hazard Mapping System Fire and Smoke analysis from the National Oceanic and Atmospheric Administration. Notice that the smoke is heading eastward, out to sea:

August 15, 2018, analysis from NOAA. Read more about this image. It might look as if the U.S. Gulf coast has a reprieve from hazy skies, but not so. We have African dust.

Of course, North America’s west coast – where fires are raging most severely now – is experiencing North America’s smokiest skies. Some western cities – for example, Portland, Oregon – are issuing alerts on air quality. The air in western North America has been heavy with smoke this summer, and I personally know that’s a problem; I got month-long bronchitis a few summers ago after camping in Colorado under skies laden with wildfire smoke.

On the up side, Les said, this is a great opportunity to look for blue moons and suns. They’re not to be confused with the sorts of Blue Moons that aren’t related to color, but which are Blue Moons in name only. There are, indeed, also actual blue-colored moons and or blue-colored suns that can be seen when wildfire smoke fills the air, if, as Les explained:

… the smoke particles are in a narrow size range of one to a few microns across. Then they scatter light in a way that filters out red and green to leave a truly blue moon or sun.

Needless to say, blue-colored moons and suns are rare.

So, if you’re in North America, watch your sunrises and sunsets. You might see the stratified color layers like those shown in the photos on this page, caused, Les said, by larger smoke particles. Or, if the smoke particles are smaller, you might even see blue-colored moons or suns!

Read more: The year the sun turned blue

Suzanne Murphy submitted this image, reporting that, “Wildfire smoke has reached Wisconsin – setting sun, August 13, 2018.”

Wildfire sunset from Kelli Brown in Tillamook, Oregon, August 2018.

Bottom line: If you’re in North America, or even the U.K. or Europe toward the end of this week, watch your sunsets and sunrises. They might look unusual due to smoke from the raging wildfires in western North America.



from EarthSky https://ift.tt/2Peqv3p
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