# A question about planets/climate



## ChasingSuns (Jun 29, 2016)

So in my WIP, I would like to flip the Northern and Southern hemispheres of the planet in terms of climate. Is there a way for this to make sense? I just don't know a lot about how Earth works when it comes to such things.


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## La Volpe (Jun 29, 2016)

What do you mean by changing the climates?

As far as I understand (which isn't that far, to be fair), the climates aren't notably different in the opposite hemispheres (at least not because of the hemisphere).

Any changes in climate would be because of prevailing winds and/or distance from the equator (and maybe geography?).


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## DragonOfTheAerie (Jun 29, 2016)

The climates of the northern and Southern Hemispheres aren't really that different except for being northern and southern. It's still hottest at the equator, coldest at the poles--


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## ChasingSuns (Jun 29, 2016)

For sure. I just looked up some info on the equator. I didn't realize that most of the tropical climates lay pretty much on the equator (I thought they were mostly a little bit south of it, shows you how little I know about geography haha). In terms of prevailing winds, how might those affect climate? Also, what causes the formation of a tropical forest instead of a desert? To me it seems that the deserts would be mostly located on the equator since it's the hottest spot, but then again as I said, geography is by far not my strongest suit.


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## DragonOfTheAerie (Jun 29, 2016)

I've had to do a huge amount of research on this stuff to make my world map, and the answer is...I still don't know. I ended up trying to understand air currents and stuff and I ended up confusing myself. But I'll tell you everything I know. 
First. Deserts aren't deserts because they're hot, they're deserts because they're dry. The dryness comes from humid air not being able to reach the region for whatever reason. (That's where the confusing thing about air currents came in.) Deserts often form in the space between two high mountain ranges. The reason for this is, clouds (containing water) have to rise up and over the mountains. As the clouds rise up, the air gets colder higher up. As the air gets colder, it can hold less water. Thus, the water in the clouds gets precipitated (rained) on the way over the mountains and by the time they're over, they're pretty much gone. So the mountains protect a region from clouds, which bring rain. When it doesn't rain in a place very much, that's called a desert. An area protected from rain by mountains is called a rain shadow. I decided to make the desert in my book a rain shadow desert because I really don't know how the other kind forms. Confusing geography stuff. 
On the other hand, a rain forest will form right on the equator, especially in areas in between an ocean and a mountain range. That's for the same reason I mentioned earlier...clouds moving over a mountain range will shed all their water as they rise in altitude. The side of the mountains that faces the ocean will receive all the precipitation, and will be a much wetter environment...I think. 
Please don't listen to me and research for yourself. I've gotten myself confused by now. 
To find out why clouds bringing rain would be going in certain directions, you'll want to look at a map of global wind patterns.  I feel like that might help. 
However, you could probably just arrange deserts and forests at random and no one would care, because no one understands global wind patterns, rain shadows or any of that stuff I just tried to explain.


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## TheKillerBs (Jun 29, 2016)

Literally the only change from flipping hemispheres is that the Coriolis spin reverses direction. In the Northern hemisphere, the spin of everything from toilet flushes to tornadoes is almost always counter-clockwise. In the Southern hemisphere, it is clockwise. Everything else does not change.

As to deserts, they tend to form at about the 30Â° of latitude mark. The prevailing winds are divided into 3 (really 6) bands. From 0-30Â° are the Tropical Easterlies, these winds blow eastward towards the equator (southeast in the Northern hemisphere, northeast in the Southern hemisphere). From 30Â°-60Â° are the Prevailing Westerlies, these blow westward toward the poles (northwest in the Northern hemisphere, southwest in the Southern hemisphere). Finally from 60Â°-90Â° you have the Polar Easterlies, these blow in the same direction as the Tropical Easterlies. Rain needs humidity in the air to happen, and for the air to get sufficiently humid you need evaporation. This mostly happens from large bodies of water, so most of the time rain clouds form over the sea or by large lakes. The wind then blows some of these rain clouds into land, and that's how it rains on land. Now, contrary to popular belief, a desert is simply an area of low precipitation. It has nothing to do with heat or sand or whatever. The world's largest desert is Antarctica, after all. So for a desert region to form, something needs to block access to the rain clouds the wind would blow into it. This is usually a mountain range, although it can also simply be just too much land between it and the ocean, such as in the middle of Asia. The 30Â° mark is especially vulnerable to low precipitation because the wind blows away from it, as the Prevailing Westerlies blow towards the west and poles and the Tropical Easterlies blow towards the east and Equator from that latitude. On the equator, the exact opposite happens, since the North Tropical Easterlies and South Tropical Easterlies converge, creating a band with high precipitation. This is where most tropical rain forests are located.

Hope this is helpful.


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## DragonOfTheAerie (Jun 29, 2016)

TheKillerBs said:


> Literally the only change from flipping hemispheres is that the Coriolis spin reverses direction. In the Northern hemisphere, the spin of everything from toilet flushes to tornadoes is almost always counter-clockwise. In the Southern hemisphere, it is clockwise. Everything else does not change.
> 
> As to deserts, they tend to form at about the 30Â° of latitude mark. The prevailing winds are divided into 3 (really 6) bands. From 0-30Â° are the Tropical Easterlies, these winds blow eastward towards the equator (southeast in the Northern hemisphere, northeast in the Southern hemisphere). From 30Â°-60Â° are the Prevailing Westerlies, these blow westward toward the poles (northwest in the Northern hemisphere, southwest in the Southern hemisphere). Finally from 60Â°-90Â° you have the Polar Easterlies, these blow in the same direction as the Tropical Easterlies. Rain needs humidity in the air to happen, and for the air to get sufficiently humid you need evaporation. This mostly happens from large bodies of water, so most of the time rain clouds form over the sea or by large lakes. The wind then blows some of these rain clouds into land, and that's how it rains on land. Now, contrary to popular belief, a desert is simply an area of low precipitation. It has nothing to do with heat or sand or whatever. The world's largest desert is Antarctica, after all. So for a desert region to form, something needs to block access to the rain clouds the wind would blow into it. This is usually a mountain range, although it can also simply be just too much land between it and the ocean, such as in the middle of Asia. The 30Â° mark is especially vulnerable to low precipitation because the wind blows away from it, as the Prevailing Westerlies blow towards the west and poles and the Tropical Easterlies blow towards the east and Equator from that latitude. On the equator, the exact opposite happens, since the North Tropical Easterlies and South Tropical Easterlies converge, creating a band with high precipitation. This is where most tropical rain forests are located.
> 
> Hope this is helpful.



The thing about toilet flushes is an urban myth, but listen to everything else because he clearly knows what he's talking about, haha.


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## RedMetalHunter (Jun 29, 2016)

The seasons are reversed in the northern and southern hemispheres, but that has to do with the angle of the earth's axis and the amount of direct sunlight.


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## La Volpe (Jun 30, 2016)

Yeah, what Killer said. I'm a bit rusty, but here is some more info on the prevailing winds (correct me if I'm wrong, Killer):

The bands form because of high and low pressure areas. So for example, around the equator, the heat from the sun is the most (because the angle is the most straight on). The heat rises, forming a low pressure system. Because of the rising air, the gap is filled up by colder air coming in from the sides. But the air coming in from sides leaves gaps so the warm air on top flows over the cold air rushing in below. 

But as the warm air travels to the colder region (away from the equator), it cools down and starts to drop. And then the process begins again. This forms a little circle of air called a hadley cell.

So now you have a system that looks something like this (if viewed from a horizontal flat surface, not space):
E = equator

ooo<--ooooooo.-->
oo/oooo\o.|oo/oooo\
o.voooo^.Eo^ooooov
oo\oooo/o^oo\oooo/
ooo-->ooo|oooo<--

But because of the Coriolis effect (based on the rotation of the planet), the winds don't just go from north to south, but take on a curve. The Wikipedia page on prevailing winds has a nice picture that shows this.

So, as Killer mentioned, when these prevailing winds carry clouds over landmass, it rains. If the landmass is too large, you'll see a lot of desert. But specifically, you'll see desert on the opposite side the prevailing winds come from (after it passes over an ocean).


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## ChasingSuns (Jun 30, 2016)

RedMetalHunter said:


> The seasons are reversed in the northern and southern hemispheres, but that has to do with the angle of the earth's axis and the amount of direct sunlight.



By reversed, do you mean for example, that when it's summer in the north it's winter in the south?


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## RedMetalHunter (Jun 30, 2016)

ChasingSuns said:


> By reversed, do you mean for example, that when it's summer in the north it's winter in the south?



Yup, exactly. CLICK HERE for a much better explanation than I provided.


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## AJ Stevens (Jun 30, 2016)

Ultimately, you can do what you like without having to really justify it too much. Which is great! Look at Earth; we have all kinds of weird anomalies that make it what it is. From El Nino to the jet stream, to one pole being more covered by ice than the other. All explainable of course, but I'd imagine most fantasy readers, while they might enjoy a light geography lesson, they won't pick up your book for the heavier stuff.


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## DragonOfTheAerie (Jun 30, 2016)

Tolkien's world isn't geologically possible and no one cares about that.


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