Green to Blue Flash

Difficult to observe, the momentary green flash above the rising or setting sun has been documented as a phenomenon caused by the atmospheric bending or refraction of sunlight. However in this sunset sequence the TWAN photographer also captured the less photographed blue flash. Like a weak prism, the Earth’s atmosphere breaks white sunlight into colors, bending red colors slightly and green and blue colors through increasingly larger angles. When the sky is clear, a green flash just above the sun’s edge can sometimes be seen for a second or so. From the photographer: “The green flash turned to blue in less than a second as a mock mirage appeared atop the Sun. I was surprised to see a green flash because due to the large anticyclone above France at the time, the atmosphere was moist. But as the sun was still rather high when the flash appeared, it became possible. And it was already lucky to see the sun at all, because the sky was covered by clouds and only a clear barre was visible at the western horizon.” Click on the second photo to see another sequence montage of this sunset.