Mapping an Earthlike planet

[derik999]

Awesome maps Akubra, extremely helpful!

[Akubra]

Thanks derik999, glad you liked them. Hope your writing and mapmaking are going smoothly!
Cheers - Akubra

[derik999]

Thanks derik999, glad you liked them. Hope your writing and mapmaking are going smoothly!
Cheers - Akubra

Thank Akubra, I appreciate it! Figuring out climates during the year is an element that I haven't taken into consideration when drawing the rough outlines of my current map. The more realistic the better. Same goes with topography. It's a fantasy world so of course I can get away with some stuff but when realism can be applied then why not?

[Azélor]

I see a couple of problems with the maps you posted.

The variation of temperature with altitude are not ok. The summits are often too cold, especially in winter. Very few places on Earth have temperature below 0 in their hot season. Outside of the high central Greenland (covers 80% of the island), most of Antarctica and some Canadian islands with mountains in the Arctic, only the high mountaintops have an average temperature below 0.

95% of Tibet is slightly hotter than that in summer, it's a tundra. Same thing in the Andes with a city like La Paz (average temperature always close to 10 degrees) https://en.wikipedia.org/wiki/La_Paz
I'm not sure what the ration altitude/temperature should be but I know that high humidity tends to limit the effect of elevation.
A thinner atmosphere mean a drastic variation in temperature, making high mountains on the poles have greater temperature variations. (can someone confirm this?)

---

About the temperature: some general rules.

Yes, the biggest factor is the latitude: places hit directly by the light from the Sun will be hotter that those receiving it at an angle. But it does not tell us why Ireland is hotter than Newfoundland or why Asia is generally colder than America at the same latitude or why the east coast are sometimes much colder than the west coasts.

Other important factors:

1-Temperature of the currents: apparently, the water does not contribute in much of the temperature difference. Because the air/winds have a larger impact on changing the temperatures. Therefore, the Gulf stream has little influence on New England and Eastern Canada because the winds are blowing to the east pushing the warm air to Europe (but a large portion is probably lost in the sea)

Humboldt current is probably one of the coldest on Earth, Chili's cost is also colder than the other west coasts.
California current is cold, it's just mild and help tempering the extremes. It's influence is only limited to the coast tough.
Benguela current is also cold but not as cold as Humbolt probably because of it's medling with a hot current: Aguihas.
The Labrador current is much colder than the Kamchatka current because it receive a lot more of cold water directly from the Arctic.
And so on.

2- Actually China is Colder than the USA only in winter but it's hotter in summer. The differences are even more extreme in Central Asia around Kazakhstan. The 2 reasons are often linked. A large landmass far from the water at high latitude can become very cold. If the winds are blowing from the sea like in Eastern Europe (Belarus, Ukraine, Western Russia), it will limit that impact. but if the winds are blowing from already cold places, it's likely to make the air even colder as in China. China is actually cold in winter compared to other places at the same latitudes, I noticed that only 1 or 2 days ago!

more later

[Akubra]

The more realistic the better. Same goes with topography. It's a fantasy world so of course I can get away with some stuff but when realism can be applied then why not?

Derik, if you want to go the "realistic way" you might be interested to read these threads:

• This is a thread in which Azelor is trying to find "climate rules" on Earth and apply them to a fictional planet.
• This, this and this are other threads which try to follow plausible rules from tectonics to ocean currents to climate.

Hope you find something to your taste!

Cheers - Akubra

[Akubra]

Azelor, thanks a lot for the long explanations.

Very few places on Earth have temperature below 0 in their hot season. Outside of the high central Greenland (covers 80% of the island), most of Antarctica and some Canadian islands with mountains in the Arctic, only the high mountaintops have an average temperature below 0.

Ok, so something that I should keep in mind. On the other hand, some of my mountain ranges are very, very high, even higher than Everest. A good example is the N/S oriented range in the middle of Nohhon, the large continent in the west. This is where two enormous plates collide and it results in the highest mountain range on the planet, over 10,000 m high. To the west of it lies a large plateau sloping down gradually from 5000 m. I can imagine that temperatures in the higher regions of that range never go over 0°C.

I'm not sure what the ration altitude/temperature should be but I know that high humidity tends to limit the effect of elevation.

This is a Wikipedia article about it. According to it a rule of thumb is 10°C/km in relatively dry air and 5.5C°/km in saturated air. But apparently it can vary a bit with other factors. This confirms what you say about humidity. So that would mean that on the rainshadow side of a mountain range it should be colder at a certain height than at the same height on the other side of the range.

You make interesting observations about the difference between water and air, regarding their impact on temperature. If I understand this correctly, ocean currents and wind direction should be handled together then, and currents would have an effect on nearby land if the wind is blowing in the direction of the land. If not, its effect would be negligible.

Looking forward to other discoveries!

Cheers - Akubra

[Azélor]

This is the article: http://www.americanscientist.org/iss...mild-climate/1

Basically, it says that the winds would be blowing differently if North America had no mountains chain to disturb it. As the air moves over the Rockies, it gets compressed and shifts south to keep to momentum because of the force of Coriolis? Personally, I'm not entirely sure it would have such a great impact. The thing is that, without mountains, the warmer air from the North Pacific would reach further inland, more like in Europe but maybe not as hot. This would probably lower the pressure center of the continent but NA would still be colder because the maritime influence has it's limits. Europe is a fairly small continent surrounded by water. So yes, the Gulf stream does not heat NA much. Also, the impact of the winds form the Gulf stream on Europe is marginal in summer when the temperature of the water are usually lower than overland.


Yes about the humidity/effect on temperature based on elevation but it gets very complicated to apply on a created world, on top on all the other things.


The other problem on you map has to do with subpolar oceanic currents. Unless the latitude is very high, the winds should blow from west to east like this : http://www.learn-eo.org/lessons/l6/i...a_ice_map2.jpg
maybe above 75 or 80.

[Akubra]

The other problem on you map has to do with subpolar oceanic currents. Unless the latitude is very high, the winds should blow from west to east like this : http://www.learn-eo.org/lessons/l6/img/l6_sea_ice_map2.jpg maybe above 75 or 80.

And I thought that my currents map was ok. Not so, it seems.

Well, I am starting to think that on the one hand all this is very interesting and absorbing, but on the other hand where does it lead to in relation to what we're trying to achieve here? My goal is to have a believable climate map. It doesn't mean that everything must be explainable. I'm not sure how deep you want to delve into this and to what level of accuracy you want to go. It's a fact that the inner workings of Earth's climate still withhold big chunks of unexplained matter from us. And I wonder, if we don't understand our own planet's climate well, how can we discover the rules to which the climate of an imaginary planet would obey?

So I think I'm going to be a bit more pragmatic about it and try to find a way to carve up my planet into the most plausibe climatic zones I'm capable of. The thing is, right now I don't really know where to start. Have you read Deadshade's tutorial about Realistic CLIMATE DESIGN for cartography? I'm tempted to give it a go, perhaps a little less general and taking into account some of my planet's peculiarities where I can. I'm going to think this over for a while...

Cheers - Akubra

[Azélor]

Well, the last thing about oceanic circulation seemed pretty important. I know I go into a lot of detail but it's important that understand the little details in order to come with a simpler system. Sometimes a lot of these details are irrelevant but unless you have an idea of the whole picture, who can't realize they are.

No we don't understand all the climate on Earth. I don't delve into thermohaline circulation or El Nino because their impact of the climate and why they form is not fully understood. Maybe the thermohaline makes the Brazil current weaker than the Gulf stream but it does not seems to have any meaningful impact ...

I just need to go into a lot of details to eventually be able to explain it simply with a model.

[Akubra]

Thanks for your explanation, Azelor. It makes a lot of sense.

I had the impression that you were trying to build a fine-tuned climate model consisting of a multitude of little steps, and that would have been a bit too much for me. Luckily that is not the case.

I'll be following your progression with a lot of interest. I'm all for a sturdy (and not too difficult ) model that can be used for many planets.

Cheers - Akubra