Sunsets in New Mexico are often vibrant with rich colors. The clean, dry air here is excellent for observing how air molecules scatter away cooler colors, leaving warmer colors at low sun angles. You can read more about why the colors of New Mexico skies are so striking here.
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In this image, you can see the clear sky on the western horizon over the Jemez Mountains. This “gap” in, or absence of clouds, to the west allows very low angle sun rays to illuminate the underside of the clouds seen in the photo.
Even when the sun has already set and is well below the horizon, rays of sunlight can transit a very long path through the atmosphere of the earth. The long path length through the atmosphere results in all the blue (cooler) colors of the spectrum being scattered away, resulting in redder (warmer) colors illuminating the clouds.
On a clear day with no clouds in the sky, atmospheric scattering like this occurs. With no clouds to reflect the low angle sunrays down to us, we do not see the reddish sunlight.
