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The TLDR for this is if I have a planet that is twice the diameter of Earth, (so four times the surface area), would continental distribution have more effect on the weather patterns than the sun and distances between the equator and the poles? Gravity is the same as Earth

More detail, this world is in a different universe that has magic, it's part of the universe from the ground up and has its own set of rules just like gravity, time, and space do here in our own world. For the purposes of this question all you need is that magic interacts with gravity in a way that reduces its effect on smaller bodies but not on larger bodies. To this end, the planet in question is roughly twice the diameter of Earth and has the same gravity as Earth, a planet the size of Jupiter would experience almost no gravitational effects from magic and neither would the stars. Due to the effects of said magic, even though the planet is much larger, atmospheric pressure would be no higher than that of Earth, the magic is a constant effect throughout, it is simply an extra physical law that affects this universe on top of our normal ones.

The planet has an even spread of oceans and continents but overall it's around 50/50 land to ocean as opposed to the 30/70 ish distribution here on Earth. There are three moons, two that are on a similar scale of Earth to our moon, both in a tight orbit with each other, the third is smaller and on the other side of the planet. There is an active magma core with tectonic activity being similar to Earth, although some tectonic plates are much larger than we have here, volcanic activity is similar to Earth.

Atmospheric composition is similar to Earth, overall the globe is similar on average to that of Earth, meaning that some of the equatorial regions are just outside of the range that humans would be able to live and survive in anything other than very small numbers, if at all. There are frozen poles similar to ours, but if you take into account that the planet has four times the surface area then again, the area around the poles that can sustain life is much further away from the poles than it is on Earth. I'm making the assumption that the poles and very hot equatorial regions are the way they are because of direct influence from the sun mixed with atmospheric composition, similar to how things work on Earth.

So my question is, if I want similar weather patterns to Earth, would the even distribution of continents and having connected oceans to allow for a thermal/saline circulation be enough to have the weather patterns I desire? Or should I factor in a variable that I've not yet thought of?

The two moons in close orbit are specifically so that tides are more variable, both moons at the right point in their orbit will cause very high tides, which would make coastal towns more of a challenge. One thing I'm completely unsure of is how this would also affect the weather systems.

I'm aware that weather is seriously chaotic, so I'm just looking for something that's believable and feels like it would work in the setting described. If there's something I've overlooked then I'd like to get it right now rather than after I've put in 200 hours working on maps!

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    $\begingroup$ A planet twice the diameter of earth would have 2X the gravity. If it only has 1X the gravity, then it has (if I recall correctly, someone check this) 0.25X the density. Either way, the weather patterns would be different and multiple moons complicate the process. Simply put, there's no scientific way to have Earth's weather on any planet that isn't pretty much entirely Earth-like. For the future, please note that (a) You're allowed one and only one question per post. (b) Questions are expected to be narrowly scoped. Climate is very complex. Try to be specific. $\endgroup$
    – JBH
    Nov 20, 2023 at 19:36
  • $\begingroup$ So gravity has a lower affect on smaller particles, meaning it's pull on tiny gas particles is much lower? Which in turn means you have less total atmosphere spread over twice the surface area? Even if you presume gravity pulled just as well on gas and you had the same total atmospheric gas spreading it over twice the surface would thin it greatly. I think humans could still breath at sea level, though they likely would get winded faster due to the lower density of air. Anyone trying to cross a mountain, or possible even a decent sized hill, will suffocate though... $\endgroup$
    – dsollen
    Nov 20, 2023 at 21:26
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    $\begingroup$ @JBH Half the density (not a quarter) at twice the radius is sufficient for equal surface gravity. $\endgroup$
    – LazyLizard
    Nov 21, 2023 at 10:56
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    $\begingroup$ You don't need magic at all to get earth like surface gravity on a super earth. Just get rid of the iron core and you are more or less done. $\endgroup$
    – LazyLizard
    Nov 21, 2023 at 12:53
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    $\begingroup$ @Frithgar If we ignore the gravity rules, then the weather is any pattern you want. What's the point of the question? $\endgroup$
    – JBH
    Nov 21, 2023 at 17:01

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Earth has 3 large scale atmospheric circulation Zones – the Hadley, Ferrel and Polar cells in each hemisphere:

These effect wind patterns and the weather

Jupiter has 8 Ferrel cells in addition to a Hadley and Polar cell in each hemisphere

The exact calculations are probably highly complex but this reference provides some indication if you are interested in calculations

So it is possible that your super earth might have an additional Ferrel atmospheric circulation cell in each hemisphere. This would produce more bands of jet streams effecting the weather, more latitudes of “trade winds”, more areas of doldrums etc. So tropical zone, hot temperate, cold temperate and polar zones. In short your super earth would have a more nuanced and detailed weather and climate than would be expected of just creating a giant version of what we see on Earth.

One note of caution, anything can be achieved with magic including wrecking a story, so use it sparingly where you really need it, keep it consistent and keep the rest well bounded by reality. And welcome to world building.

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  • $\begingroup$ I will read up some more about the Ferrel cells, thank you! And I'll also keep the word of caution in mind about the use of magic, much appreciated $\endgroup$
    – Frithgar
    Nov 21, 2023 at 22:40
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Would a world twice the size of Earth be able to have similar weather patterns?

With magic you can have anything you want there's no need to go into exhaustive details. You can have a World on top of a giant turtle and be a best seller. Your World is fairly mundane.

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  • $\begingroup$ Yes magic can handwave everything, but not everyone wants to just handwave things without thought. The very fact that the OP asked this question implies they wanted to more precisely define their magic and see the results of their world given those rules they set for their magic, not be told to ignore their own question. You could answer half the questions on this site with "a wizard did it" in theory, but that doesn't mean it's a useful answer. $\endgroup$
    – dsollen
    Nov 21, 2023 at 17:08

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