Among the many modes of transport that characters use to get around in the world of Dragon Ball, one that the story simply couldn't do without is the fabled Kintoun, sometimes also called the Flying Nimbus. The Kintoun is a flying cloud that can only be ridden by those who are pure of heart, which is why in Dragon Ball we often saw Goku or Gohan soaring around on it.
And whether it was when Goku tore off a portion of the colossal Kintoun to replace his old one, when he went zooming off aboard it with Chichi after his victory in the Tenkaichi Budokai finals, or any other scene featuring this mystical cloud, we surely weren't the only fans whose imaginations were set alight by the Kintoun.

However, if you took a logical approach to the Kintoun, just what kind of cloud would it be?
To find out, we asked Professor Ryuichi Kawamura, a researcher at Kyushu University who specializes in meteorology, to answer all of our questions about the Kintoun!

Profile

Expert: Professor Ryuichi Kawamura
Professor for the Faculty of Sciences at Kyushu University (Department of Earth and Planetary Sciences). Member of the International Research Center for Space and Planetary Environmental Sciences. Currently performing research on challenges in the fields of meteorology, climate dynamics, and natural disasters. Conducts lectures for undergraduate classes, postgraduate classes, and mentors students in their research for graduate theses, master's theses, and doctorate theses.

Interviewer: Maishiro
Entertainment analyst. Writes articles about their serious research into non-serious subjects through data analysis and interviews. His articles are often featured on Yahoo's freelance page and the Daily Portal Z website. Has a particular fondness for music, films, and manga!
Twitter: ＠_maishilo_

Contents

・Is the Kintoun a "Cumulus" or "Cumulonimbus" Cloud?
・ Anyone Can Touch a Cloud—Just Climb a Mountain!
・ The Kintoun's Incredible Speed at High Altitudes

——Firstly, what exactly are clouds made of?

Kawamura: That would be water vapor. To be a little more technical, clouds are a collection of water molecules clinging to particles in the atmosphere, which we also call an "aerosol".

Aerosols can't form very well when the air is too clean, meaning it's difficult for clouds to form in clear air. That's why it's more common to see clouds when the air is just a little bit dirty.

——Interesting! I know that there are several types of clouds that look different, but how many kinds are there?

Kawamura: If we're talking about the kinds of clouds that people see on a regular basis, such as cirrus clouds or stratus clouds, then around ten.

Different clouds form at different altitudes, generally between 2 km and 6 km above the ground. Low-level clouds up to 2 km from the earth's surface are composed of water droplets, and high-level clouds 6 km in the air and beyond are mostly ice. In between, you have mid-level clouds, which can be composed of either water droplets or ice.

——If you were to put the Kintoun into one of those categories, which would it be?

Kawamura: The Kintoun looks quite thick and smokey, right? Since its ruffles and folds are so clearly defined, I'd say that it most probably fits the description of a water droplet cloud, like a cumulus or cumulonimbus.

Thick clouds like that are formed when cloud droplets are lifted by updrafts and collect dry air around them. The droplets evaporate as they take in dry air, which leaves gaps in the cloud's outer surface and causes the bumpy, ruffled shape.

On the other hand, clouds that are formed primarily of ice particles, like cirrus clouds and cirrostratus clouds, don't evaporate so quickly, and that's why they don't have the same ruffled look as water droplet clouds do.

A ruffled appearance is evidence that a cloud is made from water droplets, and from that we also know that it can form up to around 6 km from the ground at most. The Kintoun has that same appearance, thus we know that it should be made from water droplets and that it can only exist up to around 6 km in altitude.

——That means it can't actually fly all that high, right? "Cumulonimbus" makes me think of clouds that generate bolts of lightning, but do you think it would be possible for the Kintoun to cause changes in the weather like that?

Kawamura: Hmm... The Kintoun that Goku and Gohan fly around on is pretty small, so it would be quite difficult for it to affect the weather. The electricity required for a bolt of lightning is generated by the water crystals and hail particles inside a cloud colliding, but if the cloud isn't large enough, then there won't be enough collisions, which means no lightning.

Conversely, if a cloud the size of the Kintoun did in fact contain enough water crystals and hail particles to generate lightning, it would be so dense and compressed that light wouldn't be able to travel through it at all. In either case, neither could be found in the real world.

——Goku's Kintoun looks pretty small compared to other clouds, but are there real clouds in our world of that size?

Kawamura: There are, but for us to be able to see them from the ground, clouds do need to be at least a certain size. I'd say if a cloud isn't at least a few tens of meters in length, we wouldn't be able to tell it apart from the sky.

However, if you get too close to a cloud, it actually becomes harder to see its contours. Try remembering when you've been on an airplane and flown through a cloud. While you're in there, it's hard to know what it looks like, right? For a cloud the size of the Kintoun, the closer you get, the more vague its contours would appear, but the further away you are, the harder it is to see at all, so I think that it would be hard for us to find a small cloud like that.

——There's a scene in Dragon Ball where Goku tears off a piece of the colossal Kintoun for himself, but are there any kinds of clouds that we can touch and hold like that in real life?

Kawamura: You know how when you climb up a tall mountain and there's fog all around you? Your clothes and your skin become a little damp, right? That's because you're literally inside a cloud. So in that sense, anyone who's climbed a mountain before has probably touched a cloud.

——So even if you can't really feel it with your hands, if your goal is to simply "touch a cloud", then it's possible!
As you know, the Kintoun is yellow in color, but are there any clouds like that in real life?

Kawamura: Hmm... Well, clouds themselves are actually transparent. The only reason they appear white is due to a phenomenon called "Mie scattering", where sunlight is scattered by clouds in such a way that our eyes perceive them as white. If clouds are at lower altitudes, or if they contain a higher density of cloud droplets, then sunlight becomes obstructed, making the clouds appear more grey or black.

If the sun was very low in the sky, such as during sunrise or sunset, then it would be possible for clouds to appear yellow.

——Another reason the Kintoun is so appealing is that it can fly freely through the air. Could you explain how clouds float in the real world?

Kawamura: The reasons that clouds float in the real world are that one, they cannot fall quickly, and two, they disappear too quickly.

A cloud droplet's core is an incredibly small aerosol particle 0.01 μm in length. When something is that small, it can't fall down in a straight line—it's constantly colliding with other things as it falls. For that reason, it takes a very long time for them to fall. They can only travel around 10 m toward the ground over the course of an hour. And then since they're so small, once they fall down to a certain altitude, they evaporate and disappear. That's why to us, clouds look like they're always just floating.

——So it's not that they're flying, it's that they can't fall! I'm starting to get interested in real-life clouds now too!

——Another aspect of the Kintoun is that it can fly at incredible speeds. How fast can clouds travel in real life?

Kawamura: Clouds can generally only move by being pushed by the wind, so their speed is around the same as wind speed.

That being said, wind can travel extremely fast at high altitudes. For example, there are winds called jet streams that can travel up to 100 m a second when receiving westerlies, so the clouds floating in those areas can move very fast indeed.

——In that case, maybe when Goku or Gohan are riding the Kintoun, it's actually moving together with some kind of high-speed wind.

Kawamura: There would also be quite a large burden on the body when traveling at high speeds due to wind resistance—if you're going twice as fast, for example, the wind resistance is typically four times as strong. I don't think a regular person like us would be able to handle it. There are scenes in Dragon Ball where Gohan is standing up while riding the Kintoun, but we'd have to be laying down flat to reduce the surface area travelling against the wind as much as possible.

The bullet train has a streamlined form for that same reason—to reduce the surface area exposed to oncoming air in order to reduce wind resistance while also still being able to carry a high number of passengers. Even if you were flying on the Kintoun up in the stratosphere, where wind resistance would be around one tenth that of the surface due to the air being thinner, it'd still be better to be laying down flat instead of standing.

——Do you think that Goku and Gohan flying around at high speeds on the Kintoun would have some kind of effect on the atmosphere around them?

Kawamura: The way Gohan rides the Kintoun here creates the most wind resistance, so he would probably disturb the air that he passes through and create eddies. Regardless of their number, those eddies would most likely have an effect on the clouds around them, yes.

For example, when an airplane travels, it causes disturbances in the air it passes through, which in the right conditions can become visible to the naked eye in the form of a phenomenon called contrails.

——Would it then be possible for Goku and Gohan to create contrails when flying around?

Kawamura: No, because unlike an airplane, Gohan doesn't produce any exhaust like water vapor or aerosols. For that reason, there's no way that he'd be able to create contrails or pollute the air.

——I see! Lastly, if you had a real Kintoun, what would you do with it?

Kawamura: I'd want to go and see a tornado! Tornados only last up to a few tens of minutes before disappearing, so it's actually quite hard to go and see one in real life. With the Kintoun's speed, I think I'd be able to get up close to one. So if I had a Kintoun, I'd probably go around investigating tornados!

——Thank you very much for the incredibly interesting interview today!