Reply With QuoteI've tried determining the pressure zones for January; I think this is within the reasonable range?
WIP: Need help with ocean currents, pressure zones, and precipitation
Hello,
I've been working on a map and lurking a bit by reading up on some guides (particularly the climate one by Azelor https://www.cartographersguild.com/s...ad.php?t=27782). Before I draw out country borders I want to figure out where my climates and biomes are, and I'm still kind of confused on how to plot out the ocean currents, pressure zones, and precipitation.
1. What should my ocean currents look like in the inland sea on the left continent (zone A) and the northern part of the right continent (zone B) look like? Does what I have look reasonable?
2. I'm still somewhat confused about how to set up my pressure centers. For example, in the guide above it mentions that the ITCZ is a continuous strip; why is it broken up by the oceans then? Additionally, why don't the relevant pressure zones cover the whole continent? If it's just the zones of pressure extremes for a region, how does one approximate the shapes?
3. What happens when different precipitation factors contradict each other? For example, I've read that cold currents result in lower precipitation, but onshore winds result in higher precipitation; what happens with onshore winds blowing onto a shore that has a cold current?
I did not start with any tectonic plate designing, but rather with a handdrawn map of one part (I switched over to GIMP after realizing it would take quite a rather large amount of paper at the scale I was at), so the mountains and coastwork outside of the NE part of the left continent may need some touch-up. So far I have an elevation map, which is left out. Latitude is in 15 degree increments. The world is the same as Earth in regards to size, inclination, etc. All help is appreciated.
I've tried determining the pressure zones for January; I think this is within the reasonable range?
The currents running southwards along the west coast of the continents, in the northern hemisphere, should be cold.
Inland sea currents are hard to predict. Sometimes they are driven as much by salinity gradients as anything else- the Arctic is one example. You could realistically make up almost anything you want, as long as it gyres the correct way, and yours does (clockwise in the northern hemisphere). Since yours reaches from the equator to 60 degrees I think I would make it cold or at least tepid, but not warm, running down the east coast. But it's going to be very difficult predicting what that might result in. On Earth there is no inland sea that large, so I don't know if it would force a desert there or not. Probably.
Yes, a sea that large makes the worldbuilding very interesting. And hard to predict, so again you can sort of do what you like.
The pressure zones are easier to figure out with January and July next to one another, but that looks ok. There is a LOT of wiggle room, since we only have one model (Earth). Playing with the pressure zones is how you can affect climate to nudge things in the direction you want, as long as you keep roughly to the guidelines.
Last edited by acrosome; 01-18-2020 at 06:43 PM.
Thank you for the feedback! The currents have been adjusted, and pressure systems for July have been created.
When you say "inland sea", do you include the Mediterranean in that even though it's connected to the Atlantic at Gibraltar? Or do you mean a completely landlocked ocean? I ask since for the western sea, there's a channel that connects it to the larger ocean.
And I'm a bit confused as as to how precipitation factors interact when they'd have opposite effects. For example, consider a mountain's rain shadow (less precipitation) that's coastal alongside a warm ocean current (higher precipitation), or as mentioned previously a strip of coast alongside a cool current (less precipitation) with an onshore wind (more precipitation). Does one factor have greater priority than the other? Do they simply cancel out leaving an area of "average" precipitation?
Updated Ocean Current Map:
January Pressure Zones:
July Pressure Zones:
Yes, even with a small connection to the ocean, like Gibraltar, I would still call that an "inland" sea. I would save "landlocked" for things like the Aral or Caspian, which might more logically be thought of as endorheic lakes. But that's just me- others will have different definitions. The issue is that the connecting straight is much, much smaller than the sea, so flow through it is climatically trivial.
Rainshadows are one thing that require a bit of judgement call, even in Azelor's method. When you work out his method, in a couple of places it mentions wet maritime influences going inland thousands of miles unless stopped by a mountain range, so that is one way it gets done. But he doesn't say what constitutes a large enough range... Really, there is a lot of fudging going on, for instance to make the Gobi, which is the rainshadow of the Himalayas. The Rockies are large enough to lead to semi-arid conditions on their eastern side, all the way to 100 degrees of longitude or so. So, if you declare a range to be big enough, then it's big enough. Presumably a stronger wet influence requires a larger range. Etc.
Other than that, I would just point out that yes precipitation influences do seem to be additive (and subtractive). Azelor's method does it this way.
Sorry I can't give better guidance, there. But this is another way that you can manage your world to be what you want it to be, rather than just what some algorithm spits out. (The other way being how nebulously defined the pressure zones are.)
The pressure zones look great, by the way.
P.S. Since that smallest continent in the lower left extends from 45 degrees almost to the equator, I personally would have had it generate separate gyres. So there would be a warm south-flowing current on it's eastern coast, and a cold north-flowing current on it's west coast. Also, that western continent is probably huge enough to form a Siberian low. Worth noting. You also have a large mountain range positioned to block it's west coast desert from progressing too far east, but the continent is also large enough that much of it's interior may be arid or semi-arid nonetheless, like Central Asia.
Last edited by acrosome; 01-21-2020 at 11:29 AM.
Thanks for the advice!
I've managed to finish what I think should be a good-enough January winds map.
That's true, I used to live in Alberta, Canada. Now, it's not a desert, in fact in places it resembles the Shire, lovely landscape, truly my heart says it's one of the most beautiful places on Earth with its many different regions. But it is very much arid. The air is extremely dry and I notice it every time I return home. It rains half as much as it does in BC, and while this is acceptable farming conditions so you could never call it a desert, it's definitely influenced by the Rockies. The further out you go, the lands become prairie, flattened out by ancient glacial movement. Today I live in the hollow of Lake Agassiz, which once covered an enormous amount of this land, and off somewhere to the west of here there's a transition uphill to the old lakebed. The conditions, in many ways, are similar to Alberta, but the humidity is higher. The starkness of Saskatchewan is because of our colonists cutting down far too many trees, and they're still recovering from that damage, as the wind across the flatlands has stripped it in places. When you consider the rain shadow in northern regions it's fun to also consider the glaciers and how they shaped the land so long ago.Originally Posted by acrosome
Often our weather blows in from the Ontario direction, or the United States, because those are not blocked by the Rockies. We are far from the sea, but can often predict when something will hit us based on the distance it's travelling. Like, a fierce snowfall in Newfoundland means a few days from then, there'll be a pretty bad snowfall here.
Another weather effect you can consider is what Calgary endures, which is the warm again-cool again they get. This severity of sudden weather changes does not happen as far away from the mountains as Edmonton, but Calgary is right in sight of them, and it captures some extremely rapid cycling changes. These are called chinook winds, and they're caused by the valley funnelling wind rapidly towards that area, and can cause 20 degree temperature differences. So that's fun! On the other side of the wind tunnel valley the opposite is experienced, and this is called a squamish. I believe these may be very regional terms. Anyway, ultimately, the point is that the way the entire range is shaped can make for a world of difference from one city to the next.
Click my banner, behold my art! Fantasy maps for Dungeons and Dragons, RPGS, novels. No obligation, free quotes. I also make custom PC / NPC / monster tokens.
Contact me: calthyechild@gmail.com or _ti_ (Discord) to discuss a map!
So I've made the map for January and July winds now; I think I had to wing it where the land-and-sea based pressure centers aren't quite connected but are awfully close, particularly up top. Thank you guys for the continued assistance!
January Winds:
July Winds:
Well, I can not comment about the winds maps as I have not the knowledge to advise you about it (for me is quite a minor thing about worldbuilding and I've never researched too much about the matter)... But I do belive that I can advise you concerning the ocean currentes circulation...Thank you for the feedback! The currents have been adjusted, and pressure systems for July have been created.
When you say "inland sea", do you include the Mediterranean in that even though it's connected to the Atlantic at Gibraltar? Or do you mean a completely landlocked ocean? I ask since for the western sea, there's a channel that connects it to the larger ocean.
And I'm a bit confused as as to how precipitation factors interact when they'd have opposite effects. For example, consider a mountain's rain shadow (less precipitation) that's coastal alongside a warm ocean current (higher precipitation), or as mentioned previously a strip of coast alongside a cool current (less precipitation) with an onshore wind (more precipitation). Does one factor have greater priority than the other? Do they simply cancel out leaving an area of "average" precipitation?
Updated Ocean Current Map:
I could not avoid notice that as far I know, you seemed to have underestimates the power of your equatorial ocean currents... You see, the equatorial counter current should be represented (as it's a very strong one and expands a few degrees). Related to that, your north and south equatorial currents are very, very latitudinally low there... Both of this currents expands as far as 15-20º degrees north and south respectively... I really think that you should look that up... It may vary your whole sistem...
I let you Earth's example so you can see how powerfull the equatorial currents actually are: https://en.wikipedia.org/wiki/Ocean_...rderless)3.png
Ah, thanks for the insight!
By counter-current, do you mean the middle-right side of the equatorial oceans where it crosses from east to west?
Posting Permissions
