Cloud-top Green Flash

May 22, 2019

Green Flash 050419

Photographer: Thom Peck 
Summary Authors: Thom Peck; Jim Foster

Shown above is a green flash at the cloud-top level as observed from Poway, California. Cloud-top flashes are quite rare. However, it’s possible to see a burst of emerald color near or on the Sun’s upper rim as it sinks behind a cloud deck (that’s low in the sky) as well as when it falls below the horizon. Keen-eyed observers sometimes detect green flashes, but usually when the sky is clear. A mirage is needed in order for the flash to be seen. Such mirages occur when warm air overrides a cooler layer of air – an inversion. The cloud-top flashes are poorly understood but likely result when an inversion is in place immediately above a cloud deck. Always be careful when looking anywhere near the Sun. Photo taken on May 4, 2019.

Photo Details: Camera: Canon EOS Rebel T6i; Exposure Time: 0.0005s (1/2000); Aperture: ƒ/13.0; ISO equivalent: 200; Focal Length: 250.0mm