Lenticular clouds, technically known as altocumulus standing lenticularis, are stationary lens-shaped clouds that form at high altitudes, normally aligned at right-angles to the wind direction. Photo by Valuca.
"A circum horizontal fire rainbow arc occurs at a rare confluence of right time and right place for the sun and certain clouds. Crystals within the clouds refract light into the various visible waves of the spectrum but only if they are arrayed correctly relative to the ground below. Due to the rarity with which all of these events happen in conjunction with one another, there are relatively few remarkable photos of this phenomena."