Is my large tropical continent too dry or not dry enough?

Question

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:

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.

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?

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 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.}