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View Full Version : DM Help Real World Nature & Society Questions for RPGs - Part 3



Yora
2014-07-08, 09:07 AM
We had two threads like this before and they tended to go for quite a while, so I am making a new one instead of starting a thread just for my current particular question.

If you have a question relating to how certain things work in nature or have been historically to better include them in your game, feel free to ask them here.
If you have a question about military technology and warfare, both historic and present, the Real World Weapons and Armor Question thread (http://www.giantitp.com/forums/showthread.php?347806-Got-a-Real-World-Weapon-or-Armour-Question-Mk-XV) is the place to go.

The particular question I am having now is what conditions have lead to the existance of the Gobi and Taklamakan deserts in China and Mongolia? The geography of my homebrew setting is roughly inspired by East Asia and a desert in roughly that area fits me really well. However, I have trouble understanding why these deserts exist in such a place.
The deserts of Africa, North America, and Australia are relatively easy to understand. Those are in regions of high temperatures throughout the year but lie north and south of the band of thick humid jungles along the equator.
http://www.kidsmaps.com/geography/images/fullsized/vegetation-world.png
But the Chinese deserts are on a latitude closer to the Great Lakes or France, which really aren't anywhere close to being deserts. Since evaporation does not seem to be a significant factor, the lack of water must come primarily from lack of rain.
Apparently it has something to do with the himalayas, but I don't completely understand the mechanics behind that. Is that the only factor, or are there more things to consider?

The exact numbers don't matter, but for my setting I'd like things to be at least somewhat plausible looking.

Palanan
2014-07-11, 07:07 PM
Originally Posted by Yora
The deserts of Africa, North America, and Australia are relatively easy to understand. Those are in regions of high temperatures throughout the year but lie north and south of the band of thick humid jungles along the equator.

High temperatures by themselves don't explain much, since the equatorial zone receives the most direct sunlight and experiences high temperatures as well. As it happens, desert conditions are prevalent at subtropical latitudes (centered on 30 N and S) because they're beneath prevailing high pressure zones caused by patterns of global atmospheric circulation. Under those conditions it's difficult for air to rise and cool, a necessary precursor for precipitation. This is the primary factor in the formation of the Sahara and the Australian deserts.


Originally Posted by Yora
The particular question I am having now is what conditions have [led] to the exist[e]nce of the Gobi and Taklamakan deserts in China and Mongolia?

For these deserts, the main factor is their location deep in the interior of a major continent, far from the oceans or other sources of moisture. This is compounded by the presence of high mountains (such as the Himalaya) and high plateaus, which serve as rainshadows by forcing moisture-bearing air to rise and condense on the front flanks of the mountain-barrier. (The interior effect is also a secondary factor for the Sahara and parts of the Australian deserts.)

On your graphic, notice that very thin band of blue along the southern flank of the Himalaya, representing montane forests. Those are humid forests watered by orographic rainfall, caused by the mountains intercepting moisture-laden air. Beyond those first mountain-slopes is the alpine tundra of the immense highlands beyond--the Tibetan Plateau. The Taklimakan is in the northern lee of both the Himalaya and the Tibetan Plateau, which means it's completely cut off from what would otherwise be a prominent source of moisture. I don't know my Central Asian paleoenvironments, but I'd assume that before subcontinental India rammed southern Eurasia to create the Himalaya, ocean winds helped create a substantially damper environment.

Also note that the Taklimakan is an extremely cold desert, which is another feature of continental interiors--they're not only too far from the moisture of oceans, but isolated from the oceans' moderating effect on climate. During the winter, Taklimakan is also exposed on the east to winds blowing in from eastern Siberia, which can drive the temperature down to nearly -30 C.

As for the Gobi, it's a classic example of an interior desert, again very cold in winter, and moderately high-altitude as well. Also note that "cold desert" in this context refers to the winter temperatures, but it's not cold year-round; the summertime temperatures easily surpass 40 C, so anything that lives there has to survive intense variation in temperature. These are hard, extreme environments, some of the toughest places to live outside of the polar zones--and, of course, the other kinds of deserts.

Jeff the Green
2014-07-11, 07:15 PM
You might bug Zahhak (http://www.giantitp.com/forums/showthread.php?282969-The-Enviromancer-Providing-useful-resources-on-climate-and-geography). He helped me with mine.

Palanan
2014-07-11, 07:56 PM
Zahhak would certainly be a great resource, but I think he's dropped off the edge of the Playground. His last activity was late November of last year.

I sent him a PM a few months ago and he never responded, so I have a feeling he's not really around here anymore.

Yora
2014-07-12, 05:30 AM
I think the general layout I have for the continent seems quite plausible.

http://spriggans-den.com/wp-content/uploads/2014/07/map-624x468.jpg

I didn't intend for the northern of the two north-south ranges to be very high, but bumping them up a bit isn't a big change.
Would the gap to the northern ocean in the north make a significant impact? Warm air moves towards cold air, so wind should blow from south to north, keeping moisture from the northern ocean from reaching the steppe, right?

I hadn't considered jungles in the south of the steppe, at the coast of the large gulf. But it probably wouldn't make any sense to not have lots of vegetation in that area?

Palanan
2014-07-12, 08:06 AM
Originally Posted by Yora
I think the general layout I have for the continent seems quite plausible.

Can you label your sketch? Right now I can't make heads or tails of it.


Originally Posted by Yora
I hadn't considered jungles in the south of the steppe, at the coast of the large gulf. But it probably wouldn't make any sense to not have lots of vegetation in that area?

Well, it depends; Yemen is on the water and look at that landscape. But if you have a large body of water with prevailing winds sweeping onshore, then some sort of forest cover is more than likely, although it depends on latitude, soil type and other factors.

If you can label your sketch, and give estimates of the latitudes for key features, I can give some general suggestions.

Yora
2014-07-12, 08:19 AM
The green shapes are forest, the thin brown ones are mountains, the big brown one the steppe, and the blue line is the ocean shoreline.

The north coast would be a bit south of the arctic circle, and the south edge of the map at a comparable range to India or Vietnam.

Palanan
2014-07-12, 08:31 AM
Do you have names for these features? It'll be a lot easier to discuss if we can talk about the Windfang Gap or the Khebbesh Plain, as opposed to Brown Squiggly Line #3.

Yora
2014-07-12, 08:41 AM
No, this is as much detail as I currently have.
But I think the basic layout should be solid enough. There's lots of jungles with the sea in the east and mountains in the west, just as you find in South America and China. On the west side of the mountains there's a barren plain, which would be expected from a rain shadow. No obvious holes that would make the whole arangement entirely implausible.

Palanan
2014-07-12, 08:47 AM
I'll have a couple comments in a little while--breakfast calls in the meantime.



EDIT:

So, a couple of quick comments.

First, your interior steppe/desert may not be as severe as you were hoping. On its eastern flank there's a wide gap, evidently hundreds of miles across, between the northern and southern mountain ranges, which is a perfect window for easterly winds to come through and bring moisture from the eastern ocean, which I presume is a substantial body of water.

And on the south of the interior steppe there's an area of forest and a body of water beyond, with no mountains or other barriers along the way, so that's another avenue for moisture to reach in. The northern reaches of this interior steppe will certainly be harsh, but the central and southern portions won't be barren by any means.

The truly extreme landscape will be to the west of your intended steppe, north of that unnamed bit of mountains in the far southwest, which will serve as a rainshadow and exacerbate the aridity that comes of being in a continental interior. The easterly winds blowing through the broad gap in the eastern mountains will spread rainfall across the central belt of your intended steppe, but little of that will reach the unmarked region to the west. That's where your barren Gobi-analogue will be.

And second, to the southeast you'll certainly have lowlands rainforest, especially if this is low-lying terrain. The forest cover on the eastern landscape, between the eastern mountains and the ocean, will depend in part on whether the eastern mountains, especially the southern portion beneath the wide gap, rise up abruptly from low plains or if there's a piedmont or gradually rising terrain leading up to them.

To the immediate west of the northern stretch of those eastern mountains, there will indeed be a hard rainshadow, but not so with the southern arm of the eastern mountains; between the winds slipping through the gap to their north and moisture coming up from the bay to the south, you'll probably have some sort of forest cover, although it's hard to say more without knowing what the winds and soils and elevation all look like.

Yora
2014-07-12, 09:28 AM
The southeast is indeed a case of poorly drawn maps. Both the mountains and the jungle are meant to go all the way south.Things got a bit wonkey when I added the coastline last.

A different question: Does anyone know anything about clothing and armor in central Asia from 0 to 1000 AD? Everything from Ukraine to China would do.
I think designs from Sotheast Asia would also work to add some variations for different cultures.

Palanan
2014-07-12, 10:09 AM
Originally Posted by Yora
The southeast is indeed a case of poorly drawn maps.

If the maps aren't updated to reflect your intentions there's not much I can do.

:smallannoyed:


Originally Posted by Yora
Does anyone know anything about clothing and armor in central Asia from 0 to 1000 AD?

As a start, you might take a look at Soldiers of the Dragon (http://www.amazon.com/Soldiers-Dragon-Chinese-General-Military/dp/1846030986/), which is an omnibus of four Osprey titles surveying Chinese military history. That should give you all manner of ideas and visual references.

For a much more detailed and academic survey, I'd recommend Ancient Chinese Warfare (http://www.amazon.com/Ancient-Chinese-Warfare-Ralph-Sawyer/dp/046502145X/) by Ralph Sawyer. That should get you started.