I read somewhere that the size of a planet can influence the number of pressure belts (the areas of high and low pressure that cycle wind, heat and moisture about the globe)enter image description here

How would you go about constructing these belts when worldbuilding and how are they affected by the planet's size? Are they also affected by the planetary tilt? (as Artifexian's Video notes how the lines of latitude are influenced by the degree of planetary tilt) I would like to know this before deciding the size of my fictional planet.

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    $\begingroup$ "horse latitudes" does that mean cancer and capricorn by any chance? $\endgroup$ – Alex Robinson Apr 1 '17 at 21:54
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    $\begingroup$ @Cursed1701 Yeah, sorry for the confusion, I literally grabbed the first diagram that showed what i was talking about as i didn't know how to describe it with words. $\endgroup$ – Hannah Apr 1 '17 at 21:59
  • $\begingroup$ Did you read this already? medium.com/universe-factory/climate-modeling-101-4544e00a2ff2 $\endgroup$ – Ville Niemi Apr 2 '17 at 20:46
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    $\begingroup$ @Ville Niemi Yeah, Its helpful, but it doesn't exactly say how size effect the pressure belts (other then big = more and small = less) $\endgroup$ – Hannah Apr 2 '17 at 20:50

I don't think there is any reliable study on that.

The only planet for which we have a reasonable of data is Earth.

We have sent probes into the atmosphere of the following worlds:

  • Venus: check the Venera missions. The environment in that planet is so hazardous that its atmosphere can be divided in three layers, from top to bottom: you're safe here in the near vacuum but for how long, clouds of sulphur acid and no this is not a joke and welcome to hell. Really. No probe that went in there could ever reach three hours of operation, and they carried very few instruments. We know the pressure is 92 times that of sea level here and there is lightning, but that's that.

  • Mars: we have sent plenty of probes there. The air is so thin that it's almost as if there was no atmosphere at all. The pressure is around 1 and 2 % of sea level here. It does have interesting weather patterns (and storms stronger than those of Earth), but research has always mostly focused on the ground, not on the atmosphere.

  • Jupiter: this guy has huge pressure belts. They are kinda pretty visible too, in visible light even, thanks to the atmosphere's composition. Problem is, no probe would last more than a couple hours in its atmosphere. It's not as hot or acid as Venus's, but it's too deep and the pressures are enormours. We have sent one probe into it, and there's another one in its way. We are going to learn a lot more about Jupiter's atmosphere but I don't think we would know enough to have a model upon which to answer the question.

  • Titan: we have sent exactly one probe in there. It did collect some atmospheric data but we don't have data on its pressure belts as far as I know.

What these four planets have in common is that they are too different from Earth for us to compare. Only Venus has about the same size and gravity, but the sheer heat and pressure, and a day that lasts six months, make it too different from us to serve as a model. Mars has about the same rotation period and the closest temperatures to ours, but the very low pressure makes it a poor choice for a comparison model. Titan's air is too cold and viscous. And don't get me started on Jupiter.

We should probably have a model for comparison when we reach some of the Earth-like planets that we keep finding around other stars, but that should take centuries.

At the end of the day, if you are building a fictional world, you make the rules. Just design your worlds's atmospheres to suit your taste.

I used to play a videogame where the protagonist lived in a gas giant. It had layers, pressure zones and convection. Part of me once said to myself "dude this is so off, there is no way a flying whale could be buoyant enough to float in this kind of atmosphere even if you stuffed its guts with hydrogen, and the wind speeds are unrealistic...". Most other parts of me said "man just chill and enjoy the game, you never complained when it was italian plumbers spanking turtles or bread loaves crawling through walls and stuff". Guess which parts won the argument?


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