Good morning interweb,
let’s worldbuild. In this series, let’s figure out how to apply this, —the köppen climate classification system— to our fantasy worlds. Specifically our fantasy words that closely resemble Earth. Prerequisites:
a map, ocean currents, and wind patterns. Videos on all of these are in the description. Next, we need to figure out our relative precipitation and temperature variations. –the climate zones are based, in part, on these two factors. As per those previous videos, we can expect relatively high precipitation to occur under low pressure areas –namely the intertropical convergence zone and the polar front– anywhere worth prevailing winds blow moist air onshore, and in regions subject to warm coastal currents. Conversely, relatively low precipitation occurs in high pressure areas —the subtropical ridges— where prevailing winds blow either offshore or parallels and land masses, in areas subject cold coastal currents, and in the interior of continents. As for temperature, expect relatively high temperatures near the equator, and in the interior of continents. Expect relatively low temperatures towards the poles and along the coasts. Also expect seasonal temperature variations to be much larger inland than along the coasts as land heats up and cools down more rapidly, and to a greater extent than water does. Mountains also play an important factor here too. Due to a thing called orthographic lift, the side of a mountain facing into the prevailing wind, the windward side, will be subject to high precipitation whilst the side away from the prevailing wind, the leeward side, will be subject to no precipitation. We call this dry area the mountains rain shadow. No spur rain shadows occur on all major mountain chains windward, leeward dry, wet windward, leeward dry, wet And of course, temperature drops off with altitude. Now remember these facts because we’ll be using them to help us finesse our climate zones as we place them. Got it?!
Cool, let’s build. Start by marking off and ignoring all your tall mountains –altitudal climate variation is beyond the scope of this video. Now, what is and isn’t considered a tall mountain is a matter of debate, and semantics, but I usually ignore anything above about 800-ish meters, which on my map looks like this. Next place your tropical climates. Tropical climates go in the equator at half of the Hadley cell, out to about 15-20° north and south. These hot, wet climates come in three main subtypes: – tropical rainforests,
– tropical monsoons,
– and tropical savannas. Tropical rainforest climates are hot and wet year-round Think the Amazon: very dense forest, little underbrush, poor soil quality, and very high biodiversity. Place your rainforests in your low-lying areas between about 0-10° north and south Like so. But why this particular shape? Ordinarily, I would Center my rainforest in the interior of my continents and fade them out to the coasts. Kind of like what’s happening in Africa. Equatorial interiors are hot and wet, just what rainforests love. But on my world, there is a big hunk and rain shadow going on here, so I shifted my rainforest to the east, leaving only a thin strip in the west. I also skewed marine forest slightly to the south here, because of the warm currents and onshore winds —rainforests love themselves some heavy precipitation. There’s only a thin sliver here because of this rainshadow. The mountains here aren’t so tall so the rain shadow isn’t quite as large, allowing for more rain forests. And finally this island flanked by the warm current is totally rainforested, but this one flanked by a cold current is only partially covered in rainforest because cold currents lower precipitation. Kind of like what we see happening in Indonesia. And that is basically the method: locate the rough zones, finesse with precipitation and temperature in mind, compare and contrast, rinse and repeat. Next up: tropical savannas. Tropical savanna climates have hot, wet summers and long, dry winters. Think of these regions as your world’s Serengeti; shrubs and tall grasses, dotted with isolated trees. Expect frequent droughts and lower biodiversity. Tropical savannas should be placed in the low-lying regions outside of rainforest areas, out about 15-20° north and south. Like so. Notice that wherever a warm current is present I extended the savanna region out to about 25-30°. You’ll see why in a bit. Also notice that if your land is thin, as is the case with these islands and this peninsula, both sides can be made savanna. And I deliberately did not fill out the range outs because next up is hot deserts. Hot deserts have very hot, dry summers and warm, dry winters. These regions will be your world’s Saharas; rolling sand dunes and/or bald rocky surfaces, little to no vegetation, save for like a few shrubs and fleshy leafless plants like cacti, and biodiversity will be low. Place your hot deserts in the poleward half of your Hadley cell, between about 10-30° north and south. Like so. Hot and dry is the name of the game here so I only place my deserts in low-lying continental interiors and in regions affected by cold currents and/or offshore winds, hence why there’s no desert here, and why we extended those savanna regions so far poleward. it’s too wet for deserts in these regions. Because of the rain shadows here and here, I stretched my desert zone further south. Oh, and if you have a thin continent, as I do here for example, any deserts present will be milder (remember the ocean moderates and subject to a lot of fog). And so with that, we are nearly done with the Hadley cell. All that’s left to do now is placed on transition zones between these climate zones. Hot steps generally have hot summers and warm winters with low but nonzero precipitation year-round. Place them anywhere between about 10-35° north and south, primarily as a thin band around deserts. And wherever you couldn’t place deserts or savannas. Like so. Finally, tropical monsoon climates have long, hot, very wet summers and short, warm, dry winters. Place these between about 5 and 15/20° north and south, again, primarily as a thin transition strip between your rainforests and savannas. Like so. Also, include tropical monsoons long costs with onshore winds… Again as a fairly thin strip. Now if any of your coastal regions lie on a large continent occupying the 30° line and off a large equatorial ocean, those areas will likely be subject to monsoon circulation. That is the prevailing winds in those regions will likely reverse for part of the year. When the winds blow onshore, conditions are hot and rainy –monsoon season–, when they blow offshore, conditions are cooler and drier —the dry season. On earth monsoons mainly occur on the Indian subcontinent, but also in parts of Africa, East and Southeast Asia, and to a lesser extent, Australia and the southwestern portions of North America. Consider this a worldbuilding rule of thumb. If you’re interested in the real science behind monsoon circulation, check out the links. Unfortunately, my world doesn’t really have many great candidates. Maybe here a little… I guess. Regardless, that was how to place your Hadley cell climate zones. Next time. We’ll fill in the rest of the map. See you then Good morning interweb! Updates: from now on, there will be two documents linked in the description of each and every video: a corrections document and a script document, complete with footnotes and sources. So if you want the complete Artifexian experience, you should go check those out. Also minimizing wrongness is a good thing. Thank you all so much for watching, and a massive thanks y’all to all the patrons who help make Artifexian a possibility. In particular: Isaac Silbert, Andrew Chehayl, Robert Hilton, World Anvil, Ripta Pasay, John Hooyer, A.E. Stephenson, and new top-tier Patron: Alexander Roper. I say it every month, you folks truly are amazing, I could not do what I do without your help. And until next time! Edgar out.