We hear TV meteorologists throw around lots of strange terms, but depending on where you live in the US, there may be some things you never hear like Parhelion, Sun Dog, or Crepuscular Rays. Find out their meaning!
Parhelion
No, a Parhelion isn’t an ancient building in Greece. Simply put, a Parhelion is a halo effect, one that creates the impression of a false sun or suns. That’s why they are also sometimes called a Sun Dog, or Mock Sun.
According to one historic account, in 1533, a Parhelion was mistakenly viewed as a miracle of three suns.
What causes a Parhelion?
The effect is caused by refraction and scattering of light from plate-shaped hexagonal ice crystals, rather than from tiny drops of water, according to the National Weather Service (NWS). These occur either in high and cold cirrus or cirrostratus clouds or within drifting, freezing moist air at low levels, something known as “diamond dust,” according to the SKYbrary of Aviation Safety. This occurs high up in the atmosphere, where temperatures are too cold for water to stay liquid. As light hits the ice, it breaks up into all the different colors, which is the same way rainbows get their color.
Seeing a Parhelion
However, for us to see it from the ground, the ice crystals need to be falling. Conditions need to be just right for this rare effect. Typically, the ice is quite small, gently drifting and floating on the wind as its hexagon of face is nearly horizontal. Every crystal breaks up the sun’s rays. However, it is only the ones forming parhelia, and those at the same level of our eyes, that we see, as they act like mirrors reflecting the light directly at us. The glimmer then occurs from individual bits of ice which come together and form the pale, false suns that are in line with the real one.
Crepuscular Rays
You’ve definitely seen these, you just didn’t know they had a name. We’ve all looked up at the clouds and saw the beam or beams of light shooting up outward at slanted angles, typically something resembling a V-shape. Now you know the name, Crepuscular Rays.
What causes the effect?
What allows us to see the beam is the particles within the air, such as dust, moisture, and/or pollutants. The sun’s rays light up these particles, scattering them into a visible beam. However, some conditions need to be present to create the effect. First, the clouds need to be darker and more shadowy in order for us to see the edges of light that form a strip. Second, depending on where the sun is in the sky, it can give different tinges of color to the light, rather than its typical yellow.
Why always a V-shape?
Even though the beams of light always seemed to have a V-shape from our perspective, they are actually shining in straight lines. It is the distance from the sun, where seen from our perspective, makes it appear as if the rays get narrower toward the light source, but it’s only an illusion.
