photo #4147796

Cloud Appreciation Society Cloud a DayShafts of light and shade rendered visible by haze in the atmosphere are known as crepuscular rays – at least, they are when you see them emanating from the direction of the Sun, for these light effects have a rarer and less familiar counterpart when you are looking the other way. Anti-crepuscular rays like these spotted by Sara Aerssens over the Indian Ocean from Addu Atoll in the Maldives can only be seen when you are looking directly away from the Sun. They appear at the beginning or end of the day with the Sun near the horizon directly behind you. Sara’s rays, which she spotted at sunset, were in fact shadows cast right across the sky by clouds blocking the Sun on the horizon behind her. A thin, high layer of ice crystals known as a Cirrostratus cloud likely provided the haze needed to scatter the evening sunlight and reveal the beams of shadow. Anti-crepuscular rays are in fact parallel but appear to converge at a point opposite the Sun due to the effect of perspective. When Sara spotted them, her rays were accompanied by small Cumulus in shadow that punctuated the calm evening sky.