Orbits and climates and seasons, oh my!
Time to blather on about some of my recent world-building developments~
I have a basic world map – rough continent shape and position, with some vague jottings of major geographical features on the continent-of-interest. The latter is the continent that my people are going to be on.
The world is a tidally-locked satellite of a gas giant, so I have been referring to the planet-facing side as the front for convenience. Since I can orient things however the devil I want. (Yay!) The continent-of-interest is the front-side continent. Also, “planet” refers to the gas giant, and “world” or “moon” refers to the world that actually has people and animals and stuff.
So! The star is a bit smaller than Sol, I forget what type I decided it was – one of those orange ones. (Sol is classed as yellow.) Which means it’s a bit smaller, a bit cooler, but of comparable enough size to estimate physics from our solar system (which is good enough for me).
For the moment, I’m making my math easy by approximating the planet’s orbital period around the sun as 400 days and the moon’s orbital period around the planet (and therefore rotational period/day length) as 8 days. (Days as in Earth days.) This means that each year is approximately 50 “days” long.
I’ve also decided that the planet’s axial tilt (and therefore the moon’s, and the moon’s plane of orbit relative to the planet’s orbit) is approximately 25 degrees, like Earth’s. And this is where it starts to get fun~
See, this would normally mean that it would have seasons similar to Earth – although less dramatic differences than on Earth because the world is a lot smaller. Similar axial tilt, etc.
But!
Gas giants, due to being so huge, give off A Lot Of Heat. In fact, they give off so much heat that my world will be receiving about as much energy from the planet as it does from the sun. And as we know, the front of the moon is always facing the planet. Always! There is no daily or seasonal variation in the quantity or angle of radiation received from the planet as there is from the sun.
As an added bonus, the energy emitted by the planet is entirely heat energy, which is readily absorbed by the atmosphere – unlike from the sun, which is mostly visible light and thus contributes less towards heating the moon. Oh, and did I mention that during the “night” of the front-side, they still receive a lot of reflected light from the planet – because it’d be facing the planet’s “day” side?
The upshot of all this is that the front of the moon will receive more heat, more consistently than the back. It will have very little day/night variance (both in temperature and in light levels) and also little seasonal variance in temperature unless I give the planet a more drastic axial tilt – like 45 degrees or something. Which I may do.
Of course, then one has to consider the back side. It has long days and long nights and seasons and receives only stellar energy, meaning it has a colder and much more variable climate. The details aren’t important to me, though.
What is important is: how would that affect global weather patterns? I mean, the fact that it would have an effect is obvious. The question is just what that effect would be.
My guess is that there would be resulting seasonal variations in major air and ocean currents – sort of like El Niño, perhaps, or like oscillating jet streams or something. I still have to do more research to figure out whether that will have enough of an effect on the front continent to be worth spending time on.
That is verrah interesting. For some reason I was picturing a northern continent and a southern continent. Also I didn’t realize that all moons keep one face to their planet (I knew that about our moon), though it makes sense when I think about it.
The “some reason” is pretty simple, actually: that’s how I originally had it configured. :P It’s changed due to… lots of reasons. And it is probably changing again, due to avoiding a snowball. Sigh.