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I have created a world map for a story I'm making. And it has been too long since I studied geography and geology. Assuming earth-like conditions, and a normal distribution of climate based on (approximate) lines of latitude (equator, tropics, arctics), what regions would have unique climates owing to atypical precipitation (very dry or very wet)? I'm assuming that forests are abundant otherwise.

I would most appreciate answers which can be explained in the context of our planet's climates and the underlying processes, so that it's easier to understand and extrapolate from.

Regarding scales: I don't know exactly how high the darkest bits should be, but assume Himalayan equivalents. Additionally the continents are Australian in size. The centre of the map is where the equator will be. Sorry for the lack of precise scale, I'll have to add that a bit later!

physical map

UPDATE: Given Kingledion's answer I have created a climate zone map, attempting to simplify the Koppen climate classifications.

Dark cyan being the coldest regions of pine forest, warming to light cyan maritime, yellow Mediterranean, dirty green savannah, bright green rain forest, orange scrub land, red desert.

climate zone map

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    $\begingroup$ Is this a world view(assume equator in center)? $\endgroup$ – user2448131 Aug 2 '16 at 0:35
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    $\begingroup$ The wettest place... would be the ocean? Unless I missed something, I'm not sure how anyplace else would be wetter. Driest would be if you've got a desert, or maybe a volcano. $\endgroup$ – Megha Aug 2 '16 at 8:55
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    $\begingroup$ Ah... once more this world in the making. Say, is the water-land distribution complete? I mean, are there other landmasses at the "other side" of this world? Or could you wrap this around a globe and call it a day... eh, planet? Second, what about the other direction? Did you build out ocean rifts? This would be important if there is any stream (which would greatly influence the weather). $\endgroup$ – Confused Merlin Aug 2 '16 at 11:23
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    $\begingroup$ Scale? Are those landmasses the size of the UK? The size of Australia? The size of Africa? Also the elevation scale is too tiny to read, even on the enlarged map. $\endgroup$ – DrBob Aug 2 '16 at 11:31
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    $\begingroup$ That map looks great. $\endgroup$ – kingledion Aug 4 '16 at 1:47
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First we have to assume that the planet's spin direction and orbital tilt are the same as Earth's. I would not assume Himalayan heights...the Himalayas are abnormally tall for mountains on earth, caused by a massive high speed plate collision that I don't see any evidence for in your map. Most mountain ranges probably topped out in the 4000m-6000m range through earth's history. Lets say your dark region in the Lesser Southlands is a ~4000m plateau surrounded by peaks up to 6000m, like the Altiplano of Peru and Bolivia.

Currents

You have a landmass that is completely exposed to the effect on oncoming currents on both coasts, so those currents will probably dominate the climate. The west coast of continents generally sees cold currents from the poles heading towards the equator (such as the California, Peru, Benguela, and Canary currents). The east coast will see warm currents from the equator to the poles (Agulhas, Gulf Stream, Brazil).

The climates that on West Coast go from Rainforest to Cool Desert to Mediterranean to Temperate Rainforest to Arctic. North America, South America, Africa/Europe, and the southern half of Africa all follow this pattern (though South Africa runs out of land in the Med zone).

The Climate son the East coast tend to go Rainforest, Wet/Dry Savannah, Humid Subtropical, Humid Cold-Winter, then Arctic. East Coast of North America is the best example. East Asia follows the patten, but has an additional monsoon bringing heavy summer rains, which I'll get into below. South America mostly follows the pattern, but doesn't have a large landmass to get the polar cold winters, after the Humid Pampas near Buenos Aires, it goes into cold dry Patagonia. Your continent would probably be this version look like this.

Atmospheric Movement

Another pattern that affect the earth is the Intertropical Convergence Zone (ICZ). This is a band of heavy rainfall that moves to the Tropic of Cancer (North) during the northern summer and to the Tropic of Capricorn in the southern summer.

Prevailing winds between the tropic and equator are westerly and towards the equator, prevailing winds between the tropics and arctic/antarctic circle are easterly and towards the poles.

Humid air tends to rise at the equator causing rainfall and dry air from high altitudes tends to descend around the tropics and cause reduced rainfall. This is the reason that the equator is blanketed in rainforest, but the tropics tend to go through deserts.

Monsoons are caused by proximity of an ocean to a land mass that will heat up and cool down much faster than the ocean. The three major Monsoon systems of earth are caused by the Sahara Desert (West African Monsoon), Tibetan Plateau (Indian Monsoon) and Siberia (East Asian Monsoon). I don't see anything large enough on your map to cause a true monsoon. Maybe some weak smi-reversing monsoons, as we'll see below.

Arctic Regions

The North Pole of earth is completely surrounded by land and acts almost like a lake. The South Pole is a continent surrounded by water which is isolated by a strong circumpolar current. Your world has neither feature, so I'm not exactly sure what would happen. I'm going to assume that permanant pack ice never reaches the continents. Winter feature strong, constant, cold south-blowing winds from the poles to 60degrees latitude. Summer features a mild poleward breeze. The poles are over water, not land, so you can't get the frigid air masses that form over Siberia or Canada. Your land masses probably never get down to -20F. A comparable situation is Trondheim, Norway, on the Arctic circle with no land north of it, the record low is -14.8C.

Summary of Regions

  • North and West Northland (NOTE: NEED BETTER CONTINENT NAMES) are subarctic to temperate rainforest (Norway)
  • Northwest Westland is Mediterranean (Spain), Central-west Westland turns to Dry Desert (Morocco).
  • South Westland is tropical savannah turning to rainforest, with cloud forests on top of the mountains (like Thailand/Indochina).
  • The islands between Westland and Greater Southland are rainforest.
  • Northwest Greater Southland is dry savannah turning to semi-desert scrub and desert (like the Sahel of Africa). This is the largest desert in your map. The region trapped by mountains on three sides in the heart of the continent is a big sea of sand.
  • South Greater Southland is cool temperate forest, like European Russia.
  • The island below Lesser Southlands are Mediterranean like Perth, Australia (this is because of the cold circumpolar current coming below Greater Southlands). Best fisheries on the planet.
  • The eastern side of the south coast of Lesser Southlands have a wet oceanic climate, like Sydney and Melbourne Australia. As you go west, and higher in altitude, the rain drop off quickly. On the coast the weather will be like Adelaide, Australia at higher altitudes you get a dry climate like the Karoo of South Africa.
  • Southeast Eastland is the biggest rainforest on your planet.
  • The central and eastern parts of Westland (inside the ring of mountains) are are dry 6-8 months of the year, and then have brief wet season brought by the ICZ, but much of the water is blocked by mountains to the south. Semi-desert scrub mixes with dry thorn forest like the Deccan Plateau in India. Against the southern mountains you get heavy rainfall as the ICZ retreats in fall, so there you get a wetter seasonal forest. Probably the best place in your planet for big safari animals.
  • The basin of North Eastland, South Northland, and Northwest Westland is a steppe, and the biggest set of grasslands on your planet. The climate is like the Black Sea basin...except this is much larger and stretches much farther north to south. The south would start to be hot and dry like Phoenix, while the north will grade into forest-steppe like Kiev, Ukraine. Best agricultural area on the planet.
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  • $\begingroup$ Note that at the left of the map is an elevation guide. 16,000 ft is the maximum elevation. $\endgroup$ – WhatRoughBeast Aug 2 '16 at 2:22
  • $\begingroup$ @WhatRoughBeast the key was left in by accident as it was for colour coding only. But you really do have good eyesight! $\endgroup$ – inappropriateCode Aug 2 '16 at 13:32
  • $\begingroup$ That is a comprehensive answer, thank you so much! I shall get around to doing a climate map at some point. Thought when you mention "there being nothing like the Tibetan plateau" RE size, the continents are meant to be Australia sized; does that effect the outcome? $\endgroup$ – inappropriateCode Aug 2 '16 at 13:33
  • $\begingroup$ Additionally, any tips for how to decide where to place rivers? Presumably the most of them will be in the wettest places. But there's the potential for some otherwise if distance/elevation/rainfall permit? $\endgroup$ – inappropriateCode Aug 2 '16 at 13:48
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    $\begingroup$ A low-lying desert like Australia is not big enough to cause a monsoon. The Sahara is ~20% larger than the entire continent of Australia, not all of which is desert. The Tibetan plateau is 20% smaller, but has average elevation of 4500m. Elevation makes that pressure differences caused by seasons more significant. Siberia is...well its big. Your continents just don't have enough land to get real temperature extremes. I doubt anything on your world would be as hot/cold/wet/dry as a place on earth. Everything is too close to an ocean. $\endgroup$ – kingledion Aug 2 '16 at 16:18
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So... while there is already a fine answer, I used my lunch break to try to figure out "what is with the ocean trenches?".

They are not inserted yet, so I tried to figure out how the continental and ocean plates do look after all... which wasn't as clear as I hoped at the beginning.

tectonic madness part one

plate tectonics

You have mountain ranges which look like they were created by plate uplift, you have hills that might be the result of an ice age glacier action and some might even be volcanoes, which love to pop up at plate rifts.

My picture does look... well... I have no idea how the plates are drifting and so at the moment I can't tell where rifts in the ocean might be after all.

If you extend the orange lines you should find stuff like underwater mountains (volcanoes) OR deep rifts. The read lines are much more likely to result in high places under water, but still... I got the feeling your world rips itself apart at this long rift right in the middle, BUT because there are volcanoes this might mean that the ocean isn't pretty deep after all.

Even more, I think this might be a pangea which was struck by unexplainable hot weather which resulted in an overall rise of water. Which means: Some of the even important parts of the landmasses are hidden below the ocean surface.

So you would end up with swallow water between the continents and more deep water outside the "where the pangea had its beaches" point.

Anyway, you are beyond the point where a restructuring would make sense. When I'm right with my outlining, you will end up with a greater body of water between a northern and southern group of continents, while the mountains might grow and the land start to extent at the water ends of the red lines. In many centuries....

weather impact

Due to swallow water, not much currents would form between the continents, but if we insert a more deep rift at all orange lines, we might get some east-west currents which will supply water from outside the continent area. You will end up with more wet climante where this happens and more dry climate where no currents pass by. Especially that... phallic island.

At the same time northern Eastland and eastern Northland and northern Lesser Southlands will get more wet climate (warm winters, wet summers).... Aaaand... I think I cannot add very much to kingledions answer after all saldy.

To be honest, the distribution of mountains, islands and water still looks like it wasn't done by tectonic forces but... well... a god who hasn't much experience in making worlds.

But maybe I'm wrong with my interpretation.

EDiT:

While staring at it for some time I think I found a useful tectonic layout... and this is indeed a pangea breaking up. Still the masculin monkey-wrench island is getting kind of... pressure; you will end up with salt lakes or death seas... have a look (its getting more confusing)

enter image description here

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  • $\begingroup$ A fine addition, thank you! A complaint from friends is that it doesn't look sensible tectonically, so you're right to be suspicious. One suggested that the only way it makes sense is if we assume that westland is a giant volcano... which exploded so enormously that most of the material landed and became lesser southlands. And that "phallic island" (lol) was an igneous extrusion from that event. Personally, I thought it looked more like a wrench. :( $\endgroup$ – inappropriateCode Aug 4 '16 at 12:09
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    $\begingroup$ well.... I didn't see your comment until I posted my edit; so the monkey-wrench island could be a impact-crater - look at middle america (yucatan?). Stuff like this can end up with a hill at its middle because of the grounds resonance to the impact. Still, that island gives me headache. $\endgroup$ – Confused Merlin Aug 4 '16 at 12:55
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    $\begingroup$ The map of this planet does not lend itself well to subdividing the various continents into plates. I would recommend one of three solutions: 1. This is a world with no plate tectonics (with all that implies). 2. There are two places divided right down the middle, that are slowly separating like Asia and North America during the Cretaceous. Lots of little islands between them. 3. Plate tectonics was not widely accepted until the 1960s. If your technology level is pre-1960, maybe don't even address the issue. $\endgroup$ – kingledion Aug 4 '16 at 12:55
  • $\begingroup$ Maybe 2. I'm going to go with 3. And hope the story gets to the point where a fan can post rationalise it better than I. $\endgroup$ – inappropriateCode Aug 4 '16 at 14:05

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