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I'm trying to figure out how weather scales with planet size, keeping other factors constant. For a specific example, say a planet with the following characteristics:

  • Twice the radius of Earth.
  • Rotates every 24 hours. (So the linear velocity of rotation is doubled, but the angular velocity is unchanged.)
  • Gravity is 1g (achieved by some means out of the scope of this question).
  • All other characteristics like atmospheric composition are the same as Earth.

How do, say, hurricanes on this planet compare to terrestrial hurricanes? They are affected by Coriolis force, which depends on angular distance, which requires twice the linear distance for the same angular distance, but is also fed by twice the linear rotational velocity.

Are they the same absolute size? Are they the same angular size (so twice the absolute size)? Or does some nonlinear scaling factor apply?

What about thunderstorms, tornadoes, blizzards and suchlike? Do common factors apply to all of them, or are there specific factors to take into account depending on the type of weather?

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  • $\begingroup$ Not a complete answer. But you can get some idea from looking at Jupiter and Saturn. Jupiter has "the Great Red Spot" which is a storm much larger than the Earth, and lasting for many tens of Earth years. Maybe there is some info about storms on gas giant planets that will give you what you need. $\endgroup$
    – puppetsock
    Commented May 7, 2021 at 16:50

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Assuming there are Earth-like temperature differentials and oceans/landmasses, hurricanes and tropical storms would be much stronger, partially because the angular momentum would be greater, but more owing to the interplay of oceans and landmasses. Larger oceans would allow for larger hurricanes, making them more common and larger/stronger. They'll have longer to build their strength before hitting the coast. The larger oceans might also create more storms/rain patterns along the coast as there's more warm air to interact with the cool, drier air of the land. If the landmasses are large and unbroken, they'll probably become much more arid and likely to have deserts in the centers, as it'll be harder for the water to reach all the way inland.

When looking at thunderstorms, more important than the raw size of the planet would be an idea of the continents' size, shape, and arrangement. That would give a good idea of where the weather patterns will likely form. Over the major continents, thunderstorms will be very similar, as they're created by the interaction of hot/cold fronts, and, just as on Earth, storm systems could span a continent or can be relatively confined.

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