Imagine a rainbow for a moment. Our ‘normal’ rainbow is something like a tall arch of color coming from a downpour. That’s not always how it looks, though! Look at this one from Lake Guntersville on Wednesday afternoon:
That ‘low bow’ near the water is a result of the high angle of the sun at the time the photo was taken (around 3-4 PM in mid-July).
A rainbow is actually part of a full circle; it’s just not always fully visible. The higher the sun (earlier in the day), the lower the bow will appear in the sky.
The closer to sunset, the higher the bow appears (like this one from June in Huntsville):
The go-to resource for all things optical, Atmospheric Optics, describes it this way:
“At sunrise or sunset a rainbow’s centre, the antisolar point, is on the horizon. The rainbow is half in the sky, a semicircle. As the sun rises the bow’s centre sinks. Eventually when the sun is 42º high only the tip of the bow is visible above the horizon. In the summer, rainbows are best seen in early morning or late afternoon when the sun is comparatively low.”
Ramona Edwards captured a faint cloud bow Wednesday evening over Huntsville:
Cloud bows are similar to rainbows; they form when light refracts in water droplets suspended above the ground in a cloud or in light precipitation that isn’t reaching the ground (“virga”).
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