SGU Science Picture Of The Week: Pretty Cloud Holes
What you are seeing here is not a poorly cloaked alien spaceship or a huge puddle in a cloud (although you’re getting warmer).
This is a type of cloud formation that goes by many names including a FallStreak Hole, Hole-Punch Cloud, Canal Cloud, etc.
This hole forms in certain cumulus clouds in the following two-step process:
- Some of the water in a cloud reaches a temperature below freezing but does not form ice crystals because there’s no particles (ice nuclei) available to initiate ice formation. Did you know that such a lack of ice nuclei can permit the temperature of this super-cooled water to drop down to -37C (-55F) or even lower. At this point, water molecules say “screw this crap” and they start bunching together in groups of five to make what’s called “intermediate ice” which isn’t quite ice yet but is no longer water either.
- When the ice crystals eventually form in the cloud, it starts a cascade of water evaporation around the newly-formed crystals that leaves a circular or elliptical hole in the cloud.
The beautiful example of this phenomenon you see here was recently seen in Victoria Australia.
The addition of a rainbow in the middle is a nice touch.
Image Credit: Reddit user Big Mac Heart Attack