[Photo from Yesterday, 28th November 2020, In Greece]
Introduction
Hey it's a me again drifter1!
Yesterday this quite strange phenomenon caught my intention and this is how this article came to be...
So, without further ado, let's get straight into it!
The Truth in the Myth
Folklore states that:
A ring around the sun or moon means rain or snow is coming soon.
This is true, in some way, but this ring or lunar halo, isn't necessarily foretelling bad weather. The phenomenon is more common during winter months, but can still occur in other seasons. In tropical climates or during hurricanes, there are high thin clouds that can cause the same phenomenon.
How and Why it is Formed
Lunar Halos resemble rainbows, with red color inside and blue color outside. Rainbows are red on the outside and blueish-purple on the inside. Lunar or sun halos are formed due to reflection, refraction and dispersion of light in ice crystals that are 6-sided prisms (hexagons).
[Image 1]
The ring is mostly colorless, but it might be possible to notice the red on the inside and blue on the outside. The colors are more noticeable in sun halos, because moonlight isn't very bright. In both cases the inner edge is sharper then the outer edge.
22-degree Halo
To get even more specific, the light that passes through these ice crystals bents at an 22° angle (approximately), creating a halo of 22 degrees. The clouds of ice crystals are very high in the atmosphere, over 6 Km, and called cirrus clouds. Each cloud contains millions of tiny ice crystals that cause refraction (splitting of light) and reflection (glinting of light).
Of course the crystals need to be oriented in respect to our eyes in order for the halo to appear. The ring can be very faint or very distinct based on the amount of cirrus clouds and/or the amount of light passing through the crystals.
[Image 2]
Double Halo
When the crystals are less-than-perfect there is also a chance to see a double halo. In such a case the crystals are more of triangular than hexagon shape, causing different sized halos, as the light passes through them.
In the case of double halos:
- the outer halo is a 22-degree halo
- the inner halo is a diffused 9-degree halo
Pyramidal Halo
There are also pyramid halos, which are even more rare. They are caused by pyramidal ice crystals.
In the case of pyramid halos one has to be very careful and be shielding both eyes when watching the Sun. As this phenomenon mostly appears around the Sun.
RESOURCES
References
- https://www.whsv.com/content/news/Notice-a-ring-around-the-moon-Heres-what-it-means-568525161.html#:~:text=According%20to%20folklore%2C%20%22A%20ring,rain%20storm%20across%20the%20south.
- https://www.wmcactionnews5.com/2020/01/15/breakdown-why-moon-can-have-halo-around-it/
- https://earthsky.org/space/what-makes-a-halo-around-the-moon
- http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/moonhalo.html
- http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/halo/22.rxml
- https://earthsky.org/todays-image/photo-moon-halo-22-degree-9-degree
Images
Final Words
And this is actually it for todays post!
See Ya!
And keep on Drifting!
