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The world I have imagined is much like Venus, with an atmosphere at "sea level" 70 times that of Earth, and temperatures at the same altitude approaching 377 degrees Celsius - with much more favorable temperature and pressure about 55km up. I used an online calculator to find these numbers (with 55000m as ha and 20 degrees Celsius as Ta). Other than my oceans toeing the supercritical line, it seems that liquid water will exist there, and presumably evaporate and regulate the heat on the planet the same way it does on Earth.

I'm unsure how temperature and pressure effect windspeed or other weather factors. I imagine that the amount of oceans is similar to Earth, so their depth and coverage of the planet are similar. And of course, with the atmosphere so much denser the atmosphere must also extend much higher above the surface than on Earth.

All other factors being the same as Earth: Would high pressure and heat create superstorms, or would the pressure dampen the weather towards stillness? Please don't worry about the effects of continents and mountains (though they are present) on wind currents. I'm more specifically interested in the higher altitudes, where temperature and pressure are friendlier.

I suspect the surface is hellish enough as it is, but I'm welcome to ideas about how the weather might be at the surface. Any other ideas on how such a hot ocean might affect weather are also welcome, but not part of the question.

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Weather gets created by differences in temperature and pressure. Why? Well, picture a cold and hot pocket of Air colliding. What happens? Well they exchange energy, trying to reach a state of equal energy. But this isn't a uniform process. Some areas cool down faster and so on. So you got this cluster♥♥♥♥ of high and low pressure, Fast and slow Winds as well as high and low Temps all around. This creates turbulence and by extension, storms, and what we call weather.

But here is the deal, you can't just increase the pressure and expect ever more violent weather. Because remember, hot air goes up, cold one goes down.

In your example, the ground could be fairly earth like in terms of wind and weather. There is so much hot air that cold one has a hard time getting there.

So what will end up happening is that you have a layer inside the atmosphere with extremely violent weather when the 2 extremes of hot air from the ground and cold air from the sky collide. And since there is so much hot and cold air, expect storms many times for extreme than on earth. But again, only for a certain layer.

If we look at Venus, we see 3 Layers.

  1. "Earth". At a hight of i belive 10km or so, the Air pressure is about the same as one earth. Winds are not very strong by Venus Standarts and you would have a hard time guessing the planet you are on.

  2. "Hell". This is the layer in which cold and hot air collide. This is by far the most violent Area.

  3. "Hell but without the Storm". The Ground layer of Air is just sort of hot. Sure you still got winds and Lightning and its generally not a good time but in terms of Weather, its fairly chill.

To close out, the Weather on the Surface would mostly just be hot with some Winds. How strong the winds are depends on a lot of stuff. But i would say not stronger then on earth. Again, there is only hot air, so no storms.

But I would have an idea on how to make to story more interesting. Lock the planet's Rotation. If the Planet is Locked, you got a Transition zone from Day to night side. This would create ultra violent weather, as all the cold air from one side of the planet collides with the hot air from the other side. This transition zone might be worse than Jupiter. You could even make something like this: the planet isn't locked to the Sun, the rotation is just very slow. Meaning you got this Jupiter Storm System raging across the planet.

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  • $\begingroup$ A year long day was a feature I considered. I didn't realize it might cause a wave of Jupiter level storming across the planet. Do you think the raging storm would effect all layers equally? $\endgroup$ – DehLeprechaun Aug 10 '20 at 16:09
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    $\begingroup$ It would for sure. Imagne 2 tsunamis 20km high, as wide as the Planets circonference and as fast as the Rotation slamming into each other. Again, hot Air rises, so you could have a Situation where are the Hot air stacks itself over the cold air. Sort of like a tsunami. This would then Rapidly cool down, meaning all this hot air rushes down pushing everything aside. With the right Orbit, rotation this Transition zone wouldnt be fun. I can write a bit more about it using an Google Docs if ya want $\endgroup$ – Erik Hall Aug 10 '20 at 16:16
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    $\begingroup$ Thanks for the offer, but don't trouble yourself. This is already far more information than I started with. I think for the sake of storytelling I will take some time to make models and then adjust things as I desire. A yearly storm is a super interesting feature, I might just assume it isn't powerful enough to pull mountains up by their roots though. $\endgroup$ – DehLeprechaun Aug 10 '20 at 16:51
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    $\begingroup$ I mean i got nothing better to do atm. Anyways, something that helps me is to create a 3D Model of the World and just "Simulate" what it looks like. The Factors for the Transition Storms are: 1. Density of the Atmo 2. Rotational Speed (Faster = more violent) 3. Distance to the Star (Higher Distance = Less Violent) 4. What the Atmo is made of 5. Geo activity of the Ground (More heat with more Activity such as Volcanos) $\endgroup$ – Erik Hall Aug 10 '20 at 18:00
  • $\begingroup$ The 1 atmosphere pressure level on Venus is more like 50km than 10km. And the clouds of sulphuric acid would be a bit of a clue that you were on Venus rather than Earth, as would the lack of oxygen. $\endgroup$ – Mike Scott Nov 17 '20 at 6:55
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TL;DR: If you want interesting weather, make it spin very fast.

Most of Earth's weather (and I think Jupiter's too) is due to baroclinic instability within the atmosphere and oceans. Differential heating -- more direct sunlight at the equator than at the poles -- is part of the effect but not all. You could have a planetary atmosphere with very strong differential heating but for which the atmosphere efficiently transports this heat to the poles, which would equilibrate and become kind of uninteresting. Venus's atmosphere, while very inhospitable and which has permanent jets, doesn't have dynamics quite like Earth or Jupiter because it doesn't rotate fast enough. The rapid rotation relative to typical flow speeds within the atmosphere can be summed up in a dimensionless number called the Rossby number. For example the Great Red Spot of Jupiter has a Rossby number around 0.01. If you want to read more, this paper is a nice review of exoplanetary atmospheres.

You asked about high pressure specifically. Deep down in Jupiter's atmosphere, the pressures are absolutely gigantic. I think there's still some debate as to whether Jupiter's weather is confined to a thin layer near the top of the atmosphere or whether there's interesting dynamics below, with a slight lean towards the second case according to some simulations of Jupiter's climate. In any case, it's perfectly plausible to imagine a planet with an atmosphere that's under much higher pressure than Earth and which still has interesting weather.

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