Those post-storm spectacular sunsets, explained
Q: Why does a spectacular sunset so often follow a late-afternoon thunderstorm? A:
Some of the important factors in a photoworthy red-orange sunset after a storm include timing, cloud patterns, the scattering of sunlight, and air quality in the lower atmosphere, according to the Storm Prediction Center of the National Weather Service and the National Oceanic and Atmospheric Administration.
Most thunderstorms occur in the late afternoon or the evening, close to sunset, when radiant heating and atmospheric instability have reached their peaks. In the aftermath of such a storm, midlevel and high clouds may be left behind, especially cirrus and altocumulus clouds that are ideal as a canvas for painting by the sun’s last rays.
Water-filled clouds in the lower atmosphere will have been depleted by the storm.
Those last rays are mostly red or orange because the longer path that light takes through the atmosphere as the sun’s angle becomes ever lower means that the wavelengths of other colors have been scattered away.
Contrary to popular belief, clean air scrubbed by a storm lets more red rays reach the viewer than dirty air would.
Dust and smog at low levels would scatter the light too much for an ideal sunset. (High-level particles like those left by a volcanic eruption, can, however, cause a red afterglow.)