How To Make Wind and Influence Climate

[Hawksguard]

Everything is proportionally the same but halved. The world is 12,000 miles in diameter around the equator, etc.

Sorry I don't have time to comment on the entirety of your post atm. Loos like JB has some awesome info for you. However, the statement above kind of flashed red when I read it. First off, I'm assuming you meant 12,000 miles in circumference around the equator, not diameter, since you said you were halving things. A planet with 1/2 the circumference of the Earth is going to have about *1/8* the volume of the Earth (and assuming it is proportional, about 1/8 the mass), which would give it physical characteristics much closer to Mars than Earth. If this is a naturally evolved planet, a lot of your breathable gasses aren't going to be gravitationally bound to your planet, and you're going to wind up with something tenuous at best. Of course, you could say that your smaller planet has a mass similar to Earth's, but then, all that extra metallic iron in your planet's mantle is going to wreak havoc with your magnetosphere, turning everyone's brain synapses into a fine paste. Your planet would also rotate somewhat more slowly since it doesn't need to go as far to get that 24 hour day, resulting in much decreased wind patterns, weather, and climate. Also, I'm not sure a lot of Earth climatology models would be comparable with a planet with that much decreased surface area.

When I was designing my world, I hit a lot of walls as well when trying to keep it habitable and similar to Earth and yet, at the same time, throw some variety in there. I managed to acquire a lot of leeway in making it a world terraformed by a highly advanced culture (with remnants of their terraforming technology still in place and functioning), but every time you tweak something it has the potential of throwing a lot of other things out of balance. For example, by making a planet where life had never evolved naturally on its own, I inadvertently deprived my developing civilizations of the primary fuel source (fossil fuels) that got humans through the industrial revolution. Whoops.

Check out this list of things needed to have a stable, habitable planet.