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I'm trying to create a continent where desert areas are as maximal and fertile coastal areas as minimal as possible.

I've been trying to find some tools to help me with this, but I've only been able to find Geoff's Climate Cookbook.

Unfortunately, Geoff's has it backwards. The Cookbook wants me to have a predefined map and then it helps me define the climates for that map. But I wanted to draw a map that would fit the climates I have in mind, not the other way around.

In short, I wanted to know how to draw a map of a continent that has a particular preponderance for a particular climate, namely hot deserts. The mountains, latitudes, winds, everything should be drawn to make as much hot deserts as possible.

Are there any resources that would help me do this? Please, bear in mind that I have absolutely no scientific knowledge regarding climates, so it should be an easy-to-understand resource.

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I'm going to give you some guidelines that will give you the result you want. I'm assuming that your planet is very much earth-like. If it's not the case, you can specify the differences so I can modify the answer later. Maybe it's not going to have any consequences though.

  • The regions located close to 30° north and south tend to be dry because, in the general atmospheric circulation, it is where the air is sucked back toward the land from the higher atmosphere. That air contains very little moisture.
  • I just said that it tends to be dry but in fact, it's not always the case. Large landmasses became so hot in summer that a low pressure system may form, which is what we could call a monsoon. That monsoon can bring a lot of rain even if it's just for a short period of time.
  • But the good thing is that not all low pressure systems will bring rain. For example, the Sahara is dry all year long despite having a low pressure system overland in summer. There are two things that can cause this dryness.

    1. A lack of a nearby ocean: although a low pressure system is favorable to precipitations, it need to gather the moisture from somewhere. The Sahara usually receive winds coming from the central part of Africa and from Arabia (in summer) so the winds are completely dry because of this. The situation is different in Asia where the winds can pick up the evaporating water from the ocean before dropping it on the continent.

    2. Mountains: Imagine if there was a tall mountain range in eastern China running north to south. In summer, the land became really hot. The winds converge to this low pressure system but the mountains will block all the moisture. The eastern coast would be a tropical rainforest, very rainy in summer and drier in winter and the west would be a desert. The mountains would need to be about 3000-4000m tall if you really want to block all the moisture (the effect of altitude on the precipitations is negligible if you go higher than that).

The direction of the winds is generally from east to west near the equator and the poles, but from west to east in mid latitudes. Again, the monsoon is a reversal of the direction of the winds and can happen both in summer and in winter if the landmass is hot/cold enough (example is the Siberian high forming over Mongolia in the winter).

Lastly, the driest desert on Earth, the Atacama (with some places receiving an average of 1mm or precipitation per year) is located on the west coast and it's not a coincidence. First, that part of South America is too small to have any monsoon season. Secondly, the western coasts is generally where the cold currents flow. The Humboldt current takes the water from the Southern Ocean back to the equator. This coldness is responsible for the high pressure systems forming in the area, which are generally dry. Also, colder water and colder winds transport less moisture than hotter ones.

  • To summarize, you need to make sure that you desert receive winds not from the oceans but form the interior of the continent. If it's from the ocean, it need to be on the west coast close to 30° or blocked by a mountain range.
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  • $\begingroup$ Thank you so very much for your response. Let me see if I got this straight: Imagine the planet is earth-like (maybe with less axial tilt, since I read elsewhere this may help form deserts). Now, let's imagine a continent like this (it's not my continent, it's just a thought experiment): 1) Rectangular, with an area aproximate to that of North America (it may be bigger), with the length paralel to the equator 2) The north coast is at 30º latitude 3) It is plain on the center and on the west 4) Is very mountanous on all the east coast How would that be desert-wise? $\endgroup$ – Pedro Gabriel May 16 '16 at 19:03
  • $\begingroup$ Forgot to add the continent is in the south hemisphere $\endgroup$ – Pedro Gabriel May 16 '16 at 19:19
  • $\begingroup$ @PedroGabriel Winds can also blow from north to south and vice-versa. Which could also bring significant precipitation on the continent. Also, West Africa receive a lot of rain during the wet season with winds blowing in the opposite direction compared to what is normal at that latitude. The reel challenge is always to figure out where the monsoon will be. You can see that it's making almost a straight line in Africa by looking on Google earth. $\endgroup$ – Vincent May 16 '16 at 23:20
  • $\begingroup$ I was thinking that by placing the north margin at 30º latitude, the dry wind from the Hadley cell would off-set the moist winds from the ocean. And that the cold ocean currents would dry the west margin, at least on the lowest latitudes... I could place mountains elsewhere at the west. (I'm not concerned with the south margin about now, I would like to keep focused on the north, east, west and center). $\endgroup$ – Pedro Gabriel May 17 '16 at 19:03
  • $\begingroup$ Or maybe if I diminish the area of my continent, then the monsoon effect will not be so pronounced... but then, I would lose the "lack of a nearby ocean" factor as a way to dry my winds... PS: I'm sorry if I'm sounding stupid... I'm really a newbie to this. $\endgroup$ – Pedro Gabriel May 17 '16 at 20:36

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