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enter image description here

That's the rough outline of my fantasy world. The entire location is somewhat shifted towards the Northern Hemisphere because you can't see the polar ice caps of the southern hemisphere.

Now, the dark green area in the south is rainforest or tropical vegetation. Central area is the desert.

How can I explain the presence of such vegetation ?Because the temperate area above the desert is also on the same latitude as the tropical below it. I need some explanations like presence of rains/winds/natural disasters/humanoid intervention ?

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  • $\begingroup$ the climate changes top to bottom. but not left to right. with the pole at the top that is exactly how it is on earth. $\endgroup$ Sep 14 '21 at 8:26
  • $\begingroup$ Yes, but equator here is somewhere near the light brown part. So if you equal distance north/south, you experience different foilage. How to explain that? $\endgroup$
    – Abhay123
    Sep 14 '21 at 10:40
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    $\begingroup$ One word: Altitude $\endgroup$
    – Humphrey
    Sep 14 '21 at 12:09
  • $\begingroup$ @Humphrey - since you propose it, flesh it out. I think that is the right answer but I only steal ideas from the comments of AlexP. I have principles you see. $\endgroup$
    – Willk
    Sep 14 '21 at 14:29
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    $\begingroup$ If equator corresponds to the desert band, then we have (imho) a bigger problem of explaining that. If that is the case, it means that Hadley cells function very different on this planet, if function at all. $\endgroup$
    – Alexander
    Sep 14 '21 at 17:44
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Here on Earth we have other kinds of forests growing at the same latitudes as tropical rainforests. In different places, of course. And we have other kinds of ecoregions overlapping the latitude ranges of tropical rainforests.

For example:

  • The temperate rainforests of Taiwan are at about the same 25°N latitude as the tropical rainforests of Cuba.

  • In Central America we have both tropical rainforests and tropical dry forests, side by side.

  • The latitude range of the broadleaf deciduous forest of eastern Australia overlaps the latitude range of the tropical rainforests of Madagascar.

Look at a climate map of Earth:

Köppen-Geiger Climate Classification Map

Köppen–Geiger climate classification map. Picture by user NVergopolan, availabe on Wikimedia under the Creative Commons Attribution 4.0 International license. Tropical rainforests are dark blue; note that they do not necessarily stretch in a nice east-west band across a continent; also note how tropical rainforests occur in a wide range of latitudes, and share that range with many other climatic regions.

Note how the Sahara is the only climate region extending west to east across the entire breadth of a continent. Note how most climate regions do not have nice east-west boundaries, and many actually extend in north-south strips. Note that the climate regions are not at all symmetrical with respect to the Equator. Note the striking difference between the distribution of climate regions in Africa and in South America, and in Europe and North America, although the continents pairwise share the same range of latitudes.

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  • $\begingroup$ you should notice that the patches of tropical rain-forest at those latitudes are small. and those climates that extend north to south are created by a difference in rainfall due to a mountain chain running north-south. it rains mainly on one side of a mountain chain. because mountain chains usually don't let moisture pass them. the difference in north america and Europe is from the influence of the ocean. if that kind of ocean influence were the cause of the difference in temperature then one would see either the east or the west part be a tropical rain-forest. $\endgroup$ Sep 14 '21 at 18:34
  • $\begingroup$ as for south africa and south america. those differences are also due to it not raining on 1 side of mountains. the winds blow mainly east to west in those parts of the planet. in africa there are mountains in the east and in america there are mountains in the west. when the wind brings the moisture it will fall out in front of the mountain making it dry on the other side. $\endgroup$ Sep 14 '21 at 18:40
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    $\begingroup$ @PostlimFort: Your observations are (mostly) true. You are well on the way to understand how come that climate regions are not nice bands circling the planet uniformly. $\endgroup$
    – AlexP
    Sep 14 '21 at 19:12
  • $\begingroup$ thanks @AlexP and Postlim Fort, i would make mountain chains barricading moisture to be one of the components of the explanation. $\endgroup$
    – Abhay123
    Sep 16 '21 at 4:54
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You can match the gyroscopic precession of the planet to the orbital period. This would essentially eliminate seasons. But allow your equator to be on a different place than the tropical rain-forests. And there would be no southern ice-cap. And it would be eternally dark at the north pole. think of a northern hemisphere winter.

The easier solution would be to scale the planet up so that the equator is in the tropical rain-forest.

https://en.wikipedia.org/wiki/Axial_precession

if you look at the stars at night then you may notice them following a circular path. this is from the earths spin. only there are 2 that don't spin but are always at the same pont. these are the poles. but on earth the place of the poles amongst the stars moves in a circle. completing one circle in about every 26,000 years. this movement of the poles is the precession of the earths axis. due to this precession the time it takes for earth to go through its cycle of seasons is about 20 minutes shorter than the time it takes to make a full lap around the sun.

Now for this to happen in a single orbit. One would need a massive star at or near the maximum luminosity. Creating an orbital period in the habitable zone to be much longer than the earths. Long enough for a large offset moon to make the presession match the orbital period. Only the star wouldn't live long enough for life to evolve. Only about a million or so years.

Again the easier solution would be to scale the planet up so that the equator is in the tropical rain-forest.

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    $\begingroup$ Pretty sure axial precession can't (realistically) proceed at near the orbital period. Precession of the Earth, as I understand it, is mainly due to the misaligned axis of the Moon's orbit (which in turn is due to being WAY too far out). $\endgroup$
    – Zeiss Ikon
    Sep 14 '21 at 17:00
  • $\begingroup$ I really really do not believe that you can have the axis of rotation of a planet precess so fast. Please provide a credible mechanism for such astonishingly fast axial precession; even a remotely credible mechanism will do. $\endgroup$
    – AlexP
    Sep 14 '21 at 17:30
  • $\begingroup$ Will read on it! Thank you $\endgroup$
    – Abhay123
    Sep 16 '21 at 4:59

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