Climate on a larger planet with different variables than Earth.

[s0meguy]

Hey there. I've been trying to figure out the climate for my planet before I fill it in with the appropriate environments. I have read a lot of advice on what an Earth sized planet should be like, but can't find any advice for planets that differ.

For example, my planet is about twice and a half the circumference of Earth (5 times its surface area) and it spins a lot faster. Also the gravity acting on the atmosphere is much stronger. Does this necessarily mean that because of the much stronger coriolis effect, there are a lot of hurricanes/cyclones compared to Earth? Maybe even some permanent ones, or an area that is constantly spewing out hurricanes. This might make some areas of the world uninhabitable. Maybe even a lot of the area around the tropics, where the wind would be the strongest? Maybe thunderstorms would be a lot more common at the equator.

Also, the Earth is divided in 2 horse latitudes and the ITCZ between them, with the winds flowing to the ITCZ and the polar regions from the horse latitudes. I have been trying to figure out if my planet would have more than 2 horse latitude-like bands that are progressively colder, because of its increased size?

Can you guys think of what other general climate differences there would be, because of a larger size, higher gravity, higher spinning speed? Maybe the fact that theres a lot more land and oceans on the planet also does something, and there are a lot more tectonic plates. Maybe there are even some climate/weather phenomenoms that are unseen on Earth! That would be interesting. But I am not knowledgable enough on climates to predict them.

Any thoughts?

[Gidde]

Do you plan on having humans live on this super-earth? I ask because high-grav planets would be really hard to live on. The stress on the musculoskeletal system from weighing a lot more and the increased atmospheric pressure would make it almost impossible to breathe and to move around.

Sorry, I know this doesn't really answer your question, but it's something you ought to have an answer for when you start writing your story (or setting or whatnot), because your readers will wonder.

[s0meguy]

There's an additional factor that probably will have an important effect: the atmosphere is twice the Earth's and it's chemical ratios are different. I wonder how higher and lower amounts of x types of gas would affect climates and weather?

Do you plan on having humans live on this super-earth? I ask because high-grav planets would be really hard to live on. The stress on the musculoskeletal system from weighing a lot more and the increased atmospheric pressure would make it almost impossible to breathe and to move around.

Sorry, I know this doesn't really answer your question, but it's something you ought to have an answer for when you start writing your story (or setting or whatnot), because your readers will wonder.

I considered that. I indeed would like humans to live on this planet, among other sentient creatures. But they are not from Earth, which doesn't exist in my universe. They evolved on this planet and thus adapted to its stronger gravity with a slightly different bone and muscular structure, among other things. A necessary and I think reasonable tradeoff as I wanted to make my world large because I don't think its very realistic for (for some, drastically) different sentient species to evolve on a planet the size of Earth. This way I can also make the world very varied climate and vegetation wise, and also politically varied, since it is much more difficult to maintain global empires when the planet is so large. At least, until the space age.

[Gidde]

Cool! Sounds like a plausible backstory too. Carry on

[dlaporte7271]

You know...I don't know how much Sci-Fi you read, but are you familiar with Robert Silverberg's Majipoor? It's a gigantic world settled by humans....I think he got by the gravity thing by making the planet less dense: http://en.wikipedia.org/wiki/Majipoor_series

Just food for thought.

How about atmospheric density...if gravity acts more forcefully on the gasses (whatever their makeup) then they are under more pressure and will behave differently yes?

dlaporte

[s0meguy]

You know...I don't know how much Sci-Fi you read, but are you familiar with Robert Silverberg's Majipoor? It's a gigantic world settled by humans....I think he got by the gravity thing by making the planet less dense: http://en.wikipedia.org/wiki/Majipoor_series

Just food for thought.

How about atmospheric density...if gravity acts more forcefully on the gasses (whatever their makeup) then they are under more pressure and will behave differently yes?

dlaporte

Yup, I did this. But I don't want it to be too low, since I want it to be a metal rich planet (metals are nice for many things, including life, they have plenty of functions in our bodies). I'm pretty sure that a low average planetary density indicates a metal poor planet. To add to that, huge planets (that are not gas planets, but rocky/terrestial ones), because of their large mass which increases their gravity and pull the planets mass more inwards, becoming more dense, will naturally assume a much higher density than a smaller planet. In other words, density increases exponentially with mass because of gravity, and a lot of mass is needed to make a large terrestial planet. I'm curious what the mass, diameter and density of the planet is that you refered to, its not in the wiki article. But you can only go so far down with the density until it becomes a gassy planet instead of a terrestial one.

And yup, the atmosphere's components, pressure and density would also have an effect. What, I'm not exactly sure... Perhaps the heavier the gas, less warmth they need to sink back to the Earth, thus creating more Hadley cells?

[dlaporte7271]

Here's another link http://www.majipoor.com/majipoor/majipoor_geography.php

One of the other nifty elements of Majipoor was the size of some of the life...especially the sea dragons. You could imagine life on a larger planet being exponentially larger as well...

There are other factors that could contribute to weather patterns as...consider the internal heating system of the planet, the size and make up of the core and any related magnetic fields that could contribute to weather phenomena. I believe that one theory about why Mars lost it's atmosphere has to do with it's smaller core and lack of magnetic field. I've also seen discussion about weather on some of the outer planets and interesting theories about why there are weather patterns on planets that weren't expected to.

What about moons? Distance from the sun? Multiple suns? Gads...this could go on forever....fun exercise to be sure.

I'm actually creating a world, in my own campaign, that has unusual conditions that will affect weather...I will have to go through this exercise myself, just to get my head around all the potential factors so I can come up with something that makes sense.

I'm sure you may have done some of this but here are a couple of other links NASA discussion of weather on other planets:

http://solarsystem.nasa.gov/scitech/....cfm?ST_ID=725 (brief talk about the weather in the solar system)
http://cseligman.com/text/planets/magnetism.htm (article about planetary cores and magnetic fields)

[kermode]

Cyclones (hurricanes) are not caused by the Coriolis effect, but by low pressure gradients. An increased Coriolis effect might make cyclones form faster, but if the other components needed to make hurricanes (warm water and a pressure change, basically) are not there, no amount of spinning will make them form. Basically hurricanes form over warm water, so if your planet contains more warm water than Earth, then it will have more hurricanes.

And I think your ideas for extra horse bands/doldums are pretty good. I don't know exactly what would happen with all that, so making more bands seems like a pretty good idea. You seem to know your stuff! I hate it when people just draw random climates in random places with no knowledge of how climatology or plate tectonics work.

[s0meguy]

Dlaporte, thanks for the links. They're very interesting. Especially for creating weird exo-planets. But this one has a more Earth-like climate. Yes, there are many important factors. Too many really to reliably know what they'd do. We have been wrong many times about the features of other planets in our own solar system, and while reading I came across quite a few phenomenon that defy explanation. There's just many things that we don't understand.

We're barely proficient at explaining climate features that we know are there, nevermind predicting hypothetical ones.

Cyclones (hurricanes) are not caused by the Coriolis effect, but by low pressure gradients. An increased Coriolis effect might make cyclones form faster, but if the other components needed to make hurricanes (warm water and a pressure change, basically) are not there, no amount of spinning will make them form. Basically hurricanes form over warm water, so if your planet contains more warm water than Earth, then it will have more hurricanes.

And I think your ideas for extra horse bands/doldums are pretty good. I don't know exactly what would happen with all that, so making more bands seems like a pretty good idea. You seem to know your stuff! I hate it when people just draw random climates in random places with no knowledge of how climatology or plate tectonics work.

I looked it up. You're right. I should've known that.

I concluded that nobody really knows for sure about what the climate system would be like on a large planet - even weather forecasts on our own planet are notoriously unreliable over more than a few days.

[Veldehar]

Yeah you've wandered into the hypothetical realm that a NASA scientist couldn't 100% answer... likely not close to 100%. Being Earth-like, but bigger, one suggestion I would make is that the increased Coriolis effect you imagine wouldn't necessarily increase wind speeds at the equator, as Earth doesn't have that effect. Rather, storms and basic wind patterns would track more directly east-west, like I think they do on Jupiter... I think, LOL.

Speaking of things we don't fully understand... think tectonics on a planet moving extra fast and being that large... what effects there?

My suggestion is to be a bit like me... in my world I ask if magic did this, what would be the real world effects? Then make an educated guess that seems plausible and stick with it! Thinking too much will drive you crazy... not that I wasn't there already. LOL.