3 days ago
Why does wildfire smoke cause vibrant sunrises and sunsets?
LANSING, Mich. (WLNS) — Over the past few weeks, Mother Nature has been putting on a show during the sunrises and sunsets, which is all thanks to the Canadian wildfire smoke that continues to move into the Midwest. Bright oranges, vibrant reds, and even pink, too. Why is this the case? It all has to do with the scattering of light.
Sunlight is a form of energy that travels in waves. Remember the acronym ROYGBIV? Or Red, Orange, Yellow, Green, Blue, Indigo, Violet — all the colors of the rainbow! Those are the colors on the visible wavelength spectrum.
Every color has a different wavelength, and a different amount of energy related back to it. For example, red and orange light have longer wavelengths while blue and violet light have shorter wavelengths. Light also interacts with particles and gas molecules in the air and our atmosphere. It can be absorbed or scattered by physical particles like smoke and pollution or the gases in the atmosphere.
The small interruption of scattering is what we call Rayleigh Scattering, while the larger interruption of scattering is called Mie Scattering.
Rayleigh Scattering is the reason why our sky is blue. When the air is clean and clear, overhead light has fewer particles and stuff to go through, which means it's going to be on the shorter side of wavelengths and will appear blue.
Mie Scattering occurs when larger particles scatter light over longer distances. Typically, during sunrise and sunset is when Mie Scattering is the strongest, and why we end up with those very red and orange sunrises and sunsets. This is because it takes longer for the light to pass through the particles of our atmosphere.
When we have wildfire smoke aloft or at the surface, we start to see Mie Scattering better because smoke or pollution particles can be larger than the incoming wavelength. Meaning that the longest wavelengths are being scattered best. Sometimes, if there is enough smoke in the air, it can block out the sun for the entire day! That's when we see the pictures that look like we are on Mars!
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