GRAND RAPIDS, Mich. (WOOD) — It’s been a hazy couple of days in West Michigan. We haven’t had much cloud cover overhead, but smoke from the wildfires to our west has filled the sky.
Several people have sent in photos of the sun in the sky, especially at sunrise and sunset. With the smoke overhead, the sun has become distinctly well-defined and red as it rises or sinks.
The reason the sun looks more red than usual has to do with the size of smoke particles and the wavelength of red light. On the visible light spectrum, red light has the longest wavelength and blue light has a shorter wavelength.
When there is no smoke overhead, the sunset and sunrise still tend to look red or orange. This is because the sun is low on the horizon and the visible light from the sun has more atmosphere to pass through before reaching the surface. Colors such as violet, blue and green have shorter wavelengths, and air particles absorb and scatter that light before it can pass through. Red and orange have longer wavelengths, so those colors are able to travel through and make it to our eyes.
During the day, there’s less atmosphere for visible light to pass through. The violet and blue light that gets scattered can still make it to our eyes, and since human eyes are very receptive to blue light, the sky looks blue. This process is known as Rayleigh scattering.
With smoke overhead, there are a lot of extra particles in the atmosphere. The added smoke particles scatter out the blue and violet light even more, accentuating the red light. The more smoke particles there are, the redder the sun will appear. This is why our sunsets and sunrises have been so vibrant.
The hazy sunshine will likely continue on Wednesday, then a shift in the upper air pattern will clear some smoke out for the end of the week.