I'm looking for a realism check on the climates of a Eurasia-like continent situated mostly in the tropics. I want to maximize tropical rainforests, savannahs, and hot semi-arid climates.

Here is my world's topography: world topography

I asked advice on a previous version of this Earth-like world here. Since then, I've reworked the big equatorial continent, breaking up mountain ranges and introducing a lowland belt strung with shallow seas along the width of my big equatorial continent in order to create contiguous savannahs and rainforests.

Here's my climate map: Note that I've marked out areas above 1000, 1500, and 2000m because it's important to know where they are due to their rain shadows and because I'm less sure how to apply climates to them. The climates I've put in these regions can be considered tentative. Also note that ocean currents deflect in unusual ways in several places because of sunken continents just under the surface.

world climates

Is my desert too small?
Given the rain shadows caused by the high mountains and the large plateau, the presence of warm and cool ocean currents on either coast, and the relative lowness of the area around the shallow inland seas, have I struck the right balance between aridity and humidity? Would my plateau be this dry considering its height (average of 1100m), would the desert extend all the way to the western archipelago as I've drawn it, and could enough moisture feasibly reach this far inland to make such an extensive rainforest--or should the savannah be predominant? To the East, I'm aiming to have a region like the Brazilian savannah, with arid highlands where the mountains come down to about 1000m. Is this realistic, or are my mountains too high there?

climate south detail

  • $\begingroup$ My mistake, I added a key. The colors are from the Koeppen climate classification, just with fewer subtypes. $\endgroup$
    – fred die
    Feb 20, 2022 at 20:44
  • $\begingroup$ Very confusing map. There are some colors in the map, which are not in the key. Where is the land and where is the ocean? $\endgroup$
    – imtaar
    Feb 21, 2022 at 13:43
  • $\begingroup$ @imtaar the first map shows which bits are land and which bits are not. I don't think overlaying the climate map on an ocean depth map has help clarify things, though. $\endgroup$ Feb 21, 2022 at 14:04
  • $\begingroup$ @imtaar my mistake, I didn't think the map would be confusing. I will edit the image for clarity. $\endgroup$
    – fred die
    Feb 21, 2022 at 15:40
  • 1
    $\begingroup$ @VogonPoet I will edit the question to be limited to a single region. $\endgroup$
    – fred die
    Feb 21, 2022 at 18:58

1 Answer 1

  1. Nobody can actually compute the climate map of a planet (which has a water cycle) given a detailed topograhical map, accurate orbital parameters, accurate data about the atmosphere and accurate data about solar irradiation.

  2. Very much less so without a detailed topograhical map, accurate orbital parameters, accurate data about the atmosphere and accurate data about solar irradiation.

  3. Your map appears sufficiently fine for the purposes of fiction, provided your story actually needs all that hot desert.

  4. Because, in the real world, which is indeed an "Earth-like world", let us consider one large hot desert, the Sahara:

    • 14,000 years ago it was larger than it is today, and as dry than it is today.

    • Then, 12,000 years ago, subtle changes in the orbit of the Earth (see Milankovitch cycles for a gentle introduction) triggered a positive feed-back loop which resulted in our dreadful Sahara transforming into a green lush grassland teeming with animals and people, with patches of forests, great lakes and plentiful rivers, full of fish and hippos and crocodiles.

    • Then, 4,500 years ago, this happy state of affairs came to an end, and the deadly desert came back.

    • Overall, we have reason to believe that this is a regular oscillation with a period of nobody knows exactly how long, but somewhere between 10,000 and 50,000 years.

      This regular oscillation of the Sahara between a happy, wet, green phase and a grim, dry, desolate phase was very important for the spread of many animal and plant species, humans among them, from Africa to Eurasia. See Sahara pump theory.

  5. Which means that if you made such maps of our very own Earth as it is today and as it was 10,000 years ago you will notice that Africa, which is indeed a "large tropical continent" had very very different climate zones. The same continent, on the same planet, in the same geological period, just 10,000 years apart.

  6. In conclusion, go with your map if it fits the story. Do not hesitate to modify it if the story needs more desert, less desert, no desert, more forest, less forest and so on.

Herding cattle in the Sahara, 5,000 years ago

Herding cattle in Tassili n'Ajjer, a rugged plateau right in the middle of the Sahara. Painting from pastoral period of the green happy days of what is now the world's largest hot desert. Reproduction available on Wikimedia, public domain.

  • $\begingroup$ Thank you for your answer, I'm aware of Milankovitch cycles and the green Sahara, and it is indeed very interesting. However, "go with your map if it fits the story" isn't the kind of response I'm looking for. $\endgroup$
    – fred die
    Feb 21, 2022 at 20:23
  • $\begingroup$ @freddie: But what else are you looking for? The point of the answer is that even for Earth, the most Earth-like world which can ever be, one specific large tropical continent would be shown very differently on climate maps at different times, separated by only a few thousand years. There is no other possible answer than, yes, your map is sufficiently fine, and you are even allowed to tweak it to a large extent if you want or need to. $\endgroup$
    – AlexP
    Feb 21, 2022 at 20:26
  • $\begingroup$ I'm specifically asking if given the mountain ranges and plateaus that I've drawn, moist air would be able to reach further inland, or if my intuition about how orographic lift works is right. An answer like this $\endgroup$
    – fred die
    Feb 21, 2022 at 20:30
  • $\begingroup$ Or, maybe rain shadows won't have such a big effect at these latitudes, and there are other factors that I don't know about. $\endgroup$
    – fred die
    Feb 21, 2022 at 20:37
  • $\begingroup$ @freddie: The bolded question is the question is literally "Is my desert too small?" I have given a real world example showing that your desert is perfectly allowed be as large or as small as you want it and need it. Nobody can compute such a map even if given detailed accurate data, because the climate of a world like Earth, with a water cycle, is a chaotic system (in the mathematical sense) and changes all the time. At the moment of the story, the climate of the world is as shown on your map. It will certainly change over centuries and millennia. Climate maps are empirical results. $\endgroup$
    – AlexP
    Feb 21, 2022 at 20:39

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