Here you see the afterglow from Friday’s sunset over Great Cove. The evening skies are starting to get more complex and colorful now as colder, less humid air moves in.
The most dramatic sunsets here occur in November through February, with the peak somewhere in the middle of that period. Why?
The explanation begins with the full rainbow of light waves that the sun always emits. At sunset, those rays are lower relative to us and, therefore, have to travel farther from our star through the atmosphere to light up what we see. For reasons we need not get into now, that longer distance apparently means that more blue and green light is filtered out before we see it. This means that we see things lighted by more red and orange light at sunset. But, there’s more.
Because the light is traveling farther at sunset, it is blocked by more of the miniscule “aerosols” in the air. These are chemicals from various sources, including human-caused pollution, wind-whipped dust, and vegetation emissions. These impurities attract water (they’re “hydroscopic”), which swells them. Less water swelling due to less humidity means more room for non-scattered light to get through to us. But, there’s still more.
In the winter, especially here in the Northeast, a good portion of our air originates in the icy Arctic, which has cleaner air due to fewer trees, less dust, and scant, if any, industrial pollution. Fewer impurities mean more light. (Image taken in Brooklin, Maine, on October 28, 2022.)