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I've pretty much finished the map of a world I'm building for a fantasy novel, but I've realised that on one of the continents I need there to be forest on both sides of a large mountain range. I've never made maps/worlds before so have had to research everything from scratch and I didn't really account for rain shadows.

The climate in this area is humid continental. The people living on the right side of the mountain have to some extent used magic to help the forest grow, but I would like the forest to exist naturally rather than have it all be down to magic.

The world is like Earth, only the land masses are different.

Is it realistic for there to be a forest to the right of this mountain range, or would this be in the rain shadow and too dry for a forest? If so, are there any other conditions I could alter to make it work?

I'll include a picture (with my crude climate colouring overlaid, though still unfinished on the other continent): (Some of the lakes are black, because I realised I had too few lakes and rivers and went back to add more.) I've circled the area I'm asking about. I had planned for both sides of this mountain range to have forests, but more so on the east side. enter image description here

EDIT:

If I add a great lake on the west side and make a deep inlet on the east coast to bring some warm water in to evaporate/make rain, does that help? Kind if like on this map (except I'd try to polish it a bit):

enter image description here

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    $\begingroup$ Any north-south oriented topological feature such as a mountain range is going to have a major effect on climate. Even in your tropical band on the western landmass, you will have rainshadow effects. My advice is, if you seek a realistic map, you must take this into account. $\endgroup$ Jul 1, 2019 at 21:27
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    $\begingroup$ How tall are the mountains? The Appalachians are rough enough to limit where wagons and railroads could go, but are low enough that there were forests on both sides of the mountains. $\endgroup$
    – Jasper
    Jul 1, 2019 at 22:51
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    $\begingroup$ @Jasper: It's not just that the Appalachians are low enough, but that you get storms moving off the Atlantic as well as from the west. See the term nor'easter: weather.gov/safety/winter-noreaster The OP's area looks like it should experience something similar. $\endgroup$
    – jamesqf
    Jul 2, 2019 at 6:41
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    $\begingroup$ The mountains are meant to be quite tall, kind of like the Himalayas in the northern half to the Alps in the south. There are some shorter mountain passes. The prevailing wind at that latitude would be the westerlies, so from west to east. On the east coast there are warm currents from the equator coming up along the coast, so maybe that would help precipitation? Would a large lake in the rain shadow area help? $\endgroup$
    – Nora R
    Jul 2, 2019 at 10:03
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    $\begingroup$ The Inlet, given that it begins between 15 and 30 degrees latitude, will certainly help to bring warm equatorial water up to that region, and thus increase precipitation. The lake on the opposite side of the mountains will only affect precipitation on that side, as moisture will be dropped by air that is forced up to higher altitude as it strikes the elevated terrain. $\endgroup$ Jul 3, 2019 at 21:01

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Yes, depending on wind patterns.

It's definitely possible for a mountain range to have significant precipitation, so long as there isn't a strong, dominant wind pattern going across the mountains.

Globally, climate patterns look like this:

enter image description here

Looking at the US, in much of the West there are large rainshadow regions. These are behind the Cascade and Rocky mountains, because there's a strong, persistent wind system from West to East. Further North, though, areas like Montana are heavily forested, despite being "behind" the mountains, because they get moisture from air currents from the North, as well.

Wind patterns on Earth are shown here. They change seasonally, in many areas, so fixed maps aren't as useful. (That map shows wind patters as they are in real time, I think.)

The Appalachians don't have any significant dry areas surrounding them, in part, because there are no major cross-mountain wind systems. Major storm systems come from multiple directions, so the effect of the mountains in regulating the climate is severely reduced. (Plus, they aren't terribly tall, so their rain shadow effect would be small, even in the case of strong prevailing winds.)

Many mountain ranges in the far North, such as the Urals in Russia, don't produce deserts because Arctic air currents provide both sides of the mountains with different moisture-rich wind systems. For the Urals, winds from the West bring warmer air from across Europe, while winds from the East bring cooler (but still relatively moist) air from across Siberia.

On your map, you could easily have wind systems dominated by Arctic winds on at least one side of your mountains, perhaps with a dominant wind system coming from the South in the other direction. Your climate pattern would be similar to that present in the Ural mountains, with forest present on both sides, but with one side markedly colder than the other.

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  • $\begingroup$ @Jasper Yep, good catch! $\endgroup$
    – ckersch
    Jul 3, 2019 at 1:24
  • $\begingroup$ Hi, thanks for your comment! From my research the prevailing wind pattern at those latitudes on my map would be west to east, so sadly it goes straight across the mountains... isn't the region on my map too far south for arctic winds? Google tells me the Ural mountains are at 60 degrees latitude. My mountains are also supposed to be quite a bit taller. $\endgroup$
    – Nora R
    Jul 3, 2019 at 20:48
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The answer is almost certainly yes, unless there is a unique localised climate (like the dry valleys in Antarctica or the Atacama Desert).

Although smaller in scale than the large continental regions your map depicts, the climate pattern of Te Waipounamu (South Island of New Zealand) is a good example of a rain shadow effect where forest is the primary biome on both sides of the mountains.

Before humans arrived and started clearing the landscape with fire, the eastern river plains were a giant podocarp forest of enormous totara, matai and kahikatea trees, with beech forest covering the high foothills. The eastern plains receive much less rainfall than the west coast, but there is easily enough water flowing through the landscape and enough rain coming off the ocean to sustain a large forest. Sadly it no longer exists, except in small isolated patches.

In this map of the original forest cover (1000AD), you can see that the dry tussock landscapes created by the prevailing rain shadow winds are mostly in high mountain valleys and plateaus. Everything else is forest.

The dry areas are still directly visible in recent satellite images.

Key things to think about:

  • Orographic rainfall is the prevailing wind, not the only wind. Rain will still come off the sea and sometimes off the mountains via storms.
  • Rivers coming down from the mountains can move large volumes of water across the landscape, and tend to create extremely fertile alluvial soil on the dry side, even if it receives less rainfall than on the wet side.
  • In areas where the forest clings to the mountains, the bushline will recede the closer towards the polar regions you are.
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Yes. Example: In western North America, there are forests of arid tree species (Juniper, Lodgepole Pine) in the rain shadow of many mountain ranges. The trees are slower-growing than their wet-side counterparts, the forests thinner and more sparse-looking.

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Certainly. A very good example is the Scandinavian peninsula. As you can see from the map below, there are lots of forest to the east of the north-south mountain range that forms much of the border between Norway and Sweden. They don't get as much rainfall as on the other side, but enough of the rain that falls on the mountains make it into the eastern valleys as rivers.

These valleys are also warmer than on the other side, since the dry air going down heats faster than the wet air going up cools. Since your mountains are rather far to the north in your world, this is an important factor.

Something that works against it in your world is that the west wind reaching your mountain range has travelled across a lot of land, giving off the moisture it picked up over the sea. You may want to include something like the Great Lakes to the west of the mountain range where the wind can pick up moisture.

enter image description here

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    $\begingroup$ The majority of the Scandinavian Peninsula lies north of 60 degrees latitude, which means it is in the Polar Cell. At latitudes this high, the Coriolis effect is significantly weaker, and as a result the prevailing wind direction is largely north to south. Thus, the north-south oriented mountain range doesn't cast much of a rain shadow. $\endgroup$ Jul 2, 2019 at 21:41
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    $\begingroup$ Are you sure about that, I live there and all the major weather systems move west to east. $\endgroup$
    – lijat
    Jul 3, 2019 at 7:38
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    $\begingroup$ I'm not certain of it, having not visited, but that was my understanding. It may be that your weather systems are influenced more by the ocean than by the polar cell? $\endgroup$ Jul 3, 2019 at 20:15
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    $\begingroup$ Hmm, it is true that Sweden is at a higher latitude than the mountain range on my map. I'll try to add a great lake or two on the west side of the mountain like you suggested. Would it help if I add a large inlet on the east coast where the warm currents from the equator can go a bit further inland and maybe evaporate and cause some rainfall? $\endgroup$
    – Nora R
    Jul 3, 2019 at 20:19
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    $\begingroup$ The inland lake certainly helps, though you might consider making it an entire lake system like the Great Lakes, fed by rivers coming down from the mountain. If your mountains are Himalaya high, though, I doubt a lot of moisture will make it across. The Scandinavian Mountains are much less tall; only 1,000 to 2,000 m in most places. $\endgroup$ Jul 4, 2019 at 7:27
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You may not need to look any further than the Andes and the Amazon basin to find an example on Earth. There is dense rain-forest "to the right" of much of the Andes mountains.

If you want forest on both sides then there is the Urals with boreal forest on both sides (Urals are obviously lower than the Andes, but still a significant mountain range).

If you look at the western end of the European Alps, they clearly hook around to the South in the vicinity of northern Italy. The natural vegetation on both sides of the North-South section is deciduous forest.

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    $\begingroup$ The prevailing wind direction around South America is East to West, though. The dry side of the mountains is to the west, and contains the Atacama desert. $\endgroup$
    – ckersch
    Jul 1, 2019 at 22:48
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    $\begingroup$ Adding to Ckersch's comment, the direction of prevailing winds affects weather patterns as well as the ocean currents which provide precipitation. In this case, the northern part of the Andes lies in the Hadley Cell, so wind are blowing East to West (and therefore dropping their moisture in the Amazon), whereas the southern part of the Andes lies in the Ferrel Cell, and has West to East winds, which drop their moisture on the coast thus forming the Valdivian Rainforest. $\endgroup$ Jul 2, 2019 at 1:23
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If you want a more exotic landscape, postulate an irrigation tunnel drilled through the mountain range to capture precipitation from the upwind side. This is pretty much Denver Colorado and the https://en.wikipedia.org/wiki/Moffat_Tunnel.

The water is then used to create a forest, possibly by having the outflow spread to a wide number of adits on the downwind side or a level canal-like structure made of rock that overflows at many points (think infinity pool).

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    $\begingroup$ Thanks! That is an interesting thought, the people living on the east side of the mountain range are supposed to be more technologically advanced than the rest of the world, so they would definitely be able to do something like that! $\endgroup$
    – Nora R
    Jul 3, 2019 at 20:49

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