Let's start with some sub categories of clouds. Over the years the study of clouds has been improved upon, but the first studies were done by Luke Howard in 1809. You can read through his findings: HERE.

I also wanted to provide you with some examples of actual clouds that can form beside our day-to-day clouds. Later on I will also cover the physics of clouds. Feel free to build upon this knowledge for your VFX. 

 

Special Clouds

 

Unlike the clouds we just studied, these are the scientific names for our clouds, not the Genera/Genus. These are clouds that don't really fit into any other category other than their own.

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Mammatus: Are clouds formed by sinking air. They resemble large singular cotton balls crowded together in the sky. When light reflects off of these clouds , it can create some beautiful color transformations. View an example of them: HERE.
 

Lenticular: These clouds resemble large convex lenses in the sky. They can form over mountains, and other high altitudes. Based on the wind direction, these clouds can also morph to form wave clouds. View an example of them: HERE.
 

Fog: You might be surprised, but fog is considered a type of cloud. Unlike most clouds, fog forms at low altitudes. However, it is still made up of water vapor, or ice crystals like a regular cloud. It extends from the ground up to 12 miles into the air.There are different variations of fog. In Canada where I live, we can experience Ice Fog. This happens when the ground becomes cold, and the surrounding temperature drops below freezing. You can read up on fog: HERE.
 

Contrails: These are classified as a type of cloud. This is because Contrails are formed out of condensation , which is tiny ice particles. Contrails form when the hot air expelled from plane engines hits the cold surrounding air of the sky. Because of the low temperature, the air freezes and forms a trail of ice. There are other forms of contrails, but we will go over them later. You can read up on Contrails: HERE.

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Flammagenitus: These clouds are formed after a form of convection hits the atmosphere. Such as after a volcano erupts. You can read up more : HERE.

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Homogenitus: These clouds are formed because of pollution, or industrial activities. You can usually find them over factories, or an industrial center. You can read up more : HERE.

 

Homomutatus: These clouds form out when contrails do not disperse. Rather they grow depending on the wind and temperature of the air. You can read up more : HERE.

 

Cataractagenitus: These clouds form over large fast moving bodies of water. Such as waterfalls. You can read up more : HERE.

 

Silvagenitus: These clouds form over forests, and are a result of the humidity from the tree canopy. You can read up more : HERE.

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Cirrus Clouds

 

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Now let's study some clouds that we have mentioned previously about. Cirrus clouds are one of the most common types of clouds. So let's study them. Cirrus clouds are a genera of sub forms of a category of clouds. So let's study those. In genera of clouds, the sub forms can be grouped by pattern-based clouds, opacity based, or generic based clouds to that category. Let's start with Cirrus's generic clouds.

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Cirrus Fibratus: As you can probably tell from the name. These clouds are thin and fibrous in appearance. They are the most common type of cloud in this genera. You can read up more : HERE.

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Cirrus Uncinus: These clouds resemble Cirrus Fibratus except for wavy or curled ends. You can see an example: HERE.

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Cirrus Spissatus: These Cirrus clouds that exist at the highest elevation of this category. They are thick and barely allow any light to pass through them.You can see an example: HERE.

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Cirrus Floccus: Based on the Latin meaning of it's name, these clouds resemble locks of cotton or wool.  You can see an example: HERE.

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Cirrus Castellanus: based again on it's Latin name, these clouds resemble castles. They have flat bases, and look like they have fluffy towers rising up out of them. You can see an example: HERE.

 

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Pattern Based Clouds

 

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Cirrus Intortus: These clouds appear wispy and twisted in the middle. You can see an example: HERE.

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Cirrus Vertebratus: These clouds resemble a backbone, or a rib cage of a person or animal in the sky. You can see an example: HERE.

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Cirrus Radiatus: Clouds that are straight wispy lines that originate from a point on the horizon. You can see an example: HERE.

 

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Extraterrestrial Atmospheres

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This might be an odd topic to cover, but by studying other atmospheres we can create a greater appreciation for our own. As well as a better way on how our atmosphere affects our cloud development.

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    - Based on which planets you study, you may read that the force of gravity is different based on the size of the planet. This is hugely important. If the planet's gravitational pull is not high enough, then the atmosphere will not form, or will be weak. A weaker atmosphere means less clouds, and a denser one means more clouds and a warmer atmosphere.

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- If we compare Mercury and Jupiter for example, we can get some extreme examples of atmospheric growth and decline. Mercury, even though it is very hot, has a very low gravitational pull for a planet. Therefore, it has almost no atmosphere, no clouds, and no discernible weather system.

 

- Jupiter on the other hand, is huge. It's gravitational pull is 2.4 times greater than Earths. Because of this, the density of the atmosphere is huge,and clouds cover the entire surface. The clouds are also over 50km deep. Instead of being formed by water particles, Jupiter's clouds are formed by ammonia crystals. Because of the density of the atmosphere, and the convection from the surface of the planet, Jupiter has visible storms raging across it. The most famous one being; The Great Red Spot.

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- One of the other factors to extraterrestrial clouds is the chemical composition of the atmosphere. As previously mentioned, Jupiter's clouds are formed out of ammonia crystals. This is because Jupiter's atmosphere contains ammonia, and other compounds. Our clouds are made up of water vapor because our atmosphere contains the building blocks for water. (oxygen, hydrogen) Clouds can be made up of anything, as long as the atmosphere containing them has the required compounds.

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Cloud Physics

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After we've covered some basic cloud types and formations, let's move onto some cloud physics. Cloud physics is the study of the growth, creation, and movement of atmospheric clouds. Not everything is known about cloud formation, and the exact creation of them. However, scientists agree that clouds in our atmosphere form based on the velocity, collision, and condensation of water vapor in the air. I'm not going to do a full essay on cloud physics, but if you wish to do further reading check out Science Direct's article on it; HERE. 

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Most of our understanding of clouds comes from of technological advancements in aircraft, spacecraft, and radar. Using radar we are able to track, and understand the movements of cloud systems. We know already that clouds have a basic three step process on how they condense and form in the atmosphere. We range cloud compositions in a scale. For example, the optical depth of a cloud is ranged on a scale from 4 to 10.

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We also have scales set for the genera of clouds. Such as the range of temperatures it will take for a cloud to freeze and create either ice, rain , or snow. For example, low level Stratus clouds freeze between 0 to -10C.

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There are two main models that scientists use to describe cloud formation and there system. One is a micro-physics model that is used to describe the composition of the cloud, and the contents. The other is  another micro-physics model that is used to describe the mass and concentration of the cloud.

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 Clouds can also contain dust, dirt and any other particle that has been lifted up into the air currents.

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