Here you see Great Cove enjoying Wednesday’s sunset afterglow. As the days get shorter, the sunsets and their afterglows will get increasingly more colorful, with more and more orange and red light reaching us.
These displays will be at their most intense from November through February here in the Northeast United States, according to a National Oceanic and Atmospheric Administration explanation. October is when Mother Nature’s meteorological troupe rehearses without all of its costumes.
As I understand it, the coloration phenomenon involves light scattering. This is what makes the sky, which is purple according to its wavelengths, appear pale blue to us during the day. All the colors of the rainbow are in sunlight, but they can reach us in different concentrations depending on conditions.
At sunset, the sunlight reaches us from a flatter perspective and, therefore, has to travel a longer distance through our dirty atmosphere to reach our eyes. The atmosphere filters out more of the blue, green, and some yellow visible light, which can make the reds and oranges more concentrated to our eyes.
Among other things, our atmosphere contains water-attracting aerosols from vegetation, animal and industrial pollutants, and other sources that also filter out colors. As the air gets increasingly colder and dryer, fewer and fewer of these aerosols survive to filter out the remaining red and orange light waves. Here’s the afterglow on October 5:
Sunsets get increasingly dramatic as you travel north in the winter toward colder, cleaner air. Anyone who has seen the Christmas evening sky in the Arctic will never forget it. (Image taken in Brooklin, Maine, on October 5 and 6, 2021.)