Halos and rainbows and sun pillars! Oh my!

Weather Headlines

It’s felt more like summer this week across Central Pennsylvania. Altoona recorded five days out of seven with high temperatures reaching into the 80s. Meanwhile, the average high for this time of year sits around 70 degrees. Not to mention, mild mornings led to a number of warm hued sunrises.

Summer-like conditions carried into the weekend which created even more fiery sunrises. But that wasn’t the only phenomenon captured in the sky. Halos, sundogs and sun pillars were also added to the mix! However, what conditions allow those to manifest?

To break down these optical effects we need to have an understanding of light. Visible light is what our eyes can see and is composed of all the colors of the rainbow. We can see these colors because a prism breaks down visible light into its component colors.

visible light
Source: National Weather Service

In the atmosphere, under certain conditions, water droplets and ice crystals can act as a prism, allowing us to see the colors that make up visible light. Its because of these properties that we get various atmospheric optical effects.

prism
Source: National Weather Service

Knowing the difference between refracted light and reflected light also helps us get a better understanding.

RefractionReflection
Refraction is the change in direction of a wave (in this case light) due to a change in its speed. This is most commonly observed when a wave passes from one medium to another at any angle other than 90° or 0°. So, when light is refracted inside a an ice crystal or water droplet in the air, its broken into its component colors. This creates the rainbow effect.Reflection of light occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. The light is not separated into its component colors because it is not being “bent” (or refracted), and all wavelengths are being reflected at equal angles.

Now that we broke down refraction and reflection, we can dive into what was captured in the sky this weekend!

Sun halo captured by Melissa

Halos

A halo is a ring or light that forms around the sun or moon as the light refracts off ice crystals in cirrus clouds. The halo is usually seen as a bright, white ring although sometimes it can have color.

Sundogs

Sundogs are colored spots of light that develop due to the refraction of light through ice crystals. They are located approximately 22 degrees either left, right, or both, from the sun, depending on where the ice crystals are present. The colors usually go from red closest to the sun, out to blue on the outside of the sundog.

Rainbows

Rainbows form when light is refracted entering a water droplet. Once the light is inside, it reflects and splits into the colors of the rainbow. You must be between rain and sun to spot one and look at the opposite side of the sky as the sun.

Sun pillar captured by Christopher

Sun Pillars

Sun pillars appear as a shaft of light extending vertically above the sun, most often at sunrise or sundown. They develop as a result of ice crystals slowly falling through the air, reflecting the sun’s rays off of them. Look for sun pillars when the sun is low on the horizon, and cirrus clouds are present.

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