Dawn Red Rainbows ~ By James Newt Perdue in the Arizona desert near Yuma.

"The temp was probably about 64F, and although almost completely overcast, there was no rain in our forecast until a slight chance in 24 to 48 hours.  When I saw it, I was in a neighborhood with wires all around me so I decided to try and reach a point not far away that was in an open area. It appeared to be disappearing so quickly that I stopped and took a picture even with the power lines visible. By the time I got to the open area (about 60 seconds later) it was almost gone."

©James Newt Perdue, shown with permission

These rainbows (the secondary shows faintly and broadly between the primary and power line pole) were likely generated by raindrops, virga, precipitating from clouds but evaporating before reaching the ground.

Light from the low sun, perhaps not even risen at ground level, has been highly reddened by its long slanting passage through the atmosphere. Raleigh scattering by air molecules is some 4X stronger for blue light than red. It yields us blue skies and gorgeous sunrises and sunsets.

Air molecules scatter sunlight in all directions leaving the sun rays that much weakened. At sunrise and sunset the rays traverse miles of dense air and much blue and green is scattered away.

The wavelength dependence of Rayleigh scattering arises from the extent of coupling between the frequencies associated with bound electrons within the atoms and the oscillating electric field of the light waves. The strength of the coupling increases as the oscillation frequencies get more similar. Higher blue light frequencies are closer to that of the electrons.

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