Terraformed Venus

[Azélor]

Isn't there a strata in Venus atmosphere where humans could survive if we managed to build floating cities? (without any terraforming)

[acrosome]

Isn't there a strata in Venus atmosphere where humans could survive if we managed to build floating cities? (without any terraforming)

Yes, using aerostats. It turns out that a breathable mix of nitrogen/oxygen would be buoyant in the Venusian atmosphere. You could just build a city inside a gigantic gasbag and float it, and manage the buoyancy to a stratum on Venus that is of reasonable temperature and pressure, which in this case would be ~50km altitude (which happens to be about 1 bar and 0C-50C). The atmosphere still wouldn't be breathable of course, but just being at 1 bar and a reasonable temperature makes the engineering involved much easier.

Actually, it turns out that something similar is true of Jupiter and Saturn...

I fixed some artifacts that probably nobody but me would ever notice, and added some minimal labels:

[acrosome]

OK, here's my preliminary shot at currents and pressure systems, for you all to rip apart!

But seriously, I'm open to any criticism at all. I'm feeling kind of weak on these subjects.

First, currents:



This was actually rather annoying. I don't have two large land masses running north/south to break the planet up in neat ways, like Earth. I'm not sure how all of those islands will affect things, but I tried to model it roughly on Southeast Asia, Malaysia, Borneo, etc. In particular, the way that currents might run between Pheobe and Artemis confounds me. (And it doesn't help that it's at the map edge.)

Also, I think that the way the currents generally run through those many channels that break the large equatorial continent in two is going to be very important for climate mapping. Any ideas?

I modeled that odd gyre south of Beta on the one in the far north Atlantic.

Here are the pressure systems and winds. Yellow is low pressure, green is high pressure:

January:



July:



Once you have beaten me up enough about these (I'm looking at you, Azelor) I'll start on humidity, temperature, etc. In particular, do you think that Ishtar (the large southern continent) is large enough to develop that big summer low?

Climate is going to be a lot of fun, with that huge continent with high mountains sitting right on the equator.

[jbgibson]

While you don’t have quite the Continental spread that earth does, it might simplify your currents (and generate other interesting effects) if you sketch in Continental shelves connecting many of the islands. If ocean is shallow enough it can plausibly steer currents almost as well as coastlines :-). Even if not extremely shallow, if a basin is cut off enough to discourage flow-through currents to drain away heat, you could get some powerful heat-engine storm drivers - see the Gulf if Mexico...

A ‘nice’ (well... interesting - maybe not so nice for the residents) effect of a bunch of warm shallow sea is the enhanced potential for cyclones/hurricanes.

[acrosome]

Thank you.

Hmmm. I'll have to look for some potential storm generators. That sounds interesting. Any ideas on what sort of shallow depths are needed? Any examples from Earth? The Caribbean is about as deep in the basins as the Atlantic, so how does that work?

But Venus doesn't have continental shelves per se. It doesn't work the way Earth does. That's why the mountains don't look "right", either. It's surface is volcanic, and relief depends upon where the lava has flowed and where the rifts have formed. The current theory is that the whole planet undergoes massive destructive resurfacing (i.e. it melts and/or drops into the mantle for recycling) every few hundred million years due to heat buildup from a lack of decent convection.

Here's one map showing some shallows (a repeat from the previous page):



I forget how shallow water had to be to be light blue- I want to say 500 feet. I can produce something again when I get home. What would be a good cut-off for ocean depths to affect currents? The Wikipedia page implies that defining a shelf is more a matter of slope than depth. Knowing what I do about Venus, most of the oceans will have enough slope almost instantly offshore, so this map might actually be decent for this purpose. Or I could have Wilbur spit out a slope map, but I might have to play around with that quite a bit to get something useful.

Some of those currents south of the equatorial continent (Aphrodite) might get really weird.

I suspect that I'm going to spend a LOT of time tweaking the currents and winds based upon input from you guys, so it may be quite a while before I even get to climate...

[Azélor]

So to sum up the info on the planet:

You rotated the map so it spins like Earth
A day is 24h
A year is 240 days
Axial tilt 20 degree


About the currents.
The map looks pretty good.
My only improvement would be the green current north of Artemis.
I would push it further east (assuming east is the right side of the map)
It makes the small red current bend, before mixing together.

[Azélor]

January pressure map:

Again in Artemis, I would push the high pressure system east, and maybe a bit south. The north west should not be affected much.
The north pole should be more like a high pressure area. Such is the case on Earth because the pole is covered with ice. But since there is not much land up there, this doesn't really matter.

Same thing with the south pole is July. The high pressure system should be expanded if there is an ice shelve.

July:

No high pressure system overland in the northern hemisphere, only over the water. Land is warmer and so the pressure lower.

The rest looks ok to me.

[acrosome]

As always, thanks for the awesome input.

So to sum up the info on the planet:

You rotated the map so it spins like Earth
A day is 24h
A year is 240 days
Axial tilt 20 degree

Correct.

My only improvement would be the green current north of Artemis.
I would push it further east (assuming east is the right side of the map)
It makes the small red current bend, before mixing together.

January pressure map:

Again in Artemis, I would push the high pressure system east, and maybe a bit south. The north west should not be affected much.
The north pole should be more like a high pressure area. Such is the case on Earth because the pole is covered with ice. But since there is not much land up there, this doesn't really matter.

Same thing with the south pole in July. The high pressure system should be expanded if there is an ice shelve.

July:

No high pressure system overland in the northern hemisphere, only over the water. Land is warmer and so the pressure lower.

The rest looks ok to me.

That's it? Damn. I was expecting a thrashing. But I guess that I have done this a few times before with input from you and Pixie, and not a lot has changed since then.

So, to feed back to you:

1. Have the current north of Artemis flow closer to the coast, as described.

2. Nudge the winter Artemesian high a bit southeast.

3. Put a high-pressure area in the center of the low-pressure areas I have around the poles in winter. (Yes, there are polar icecaps.) Should the southern one be confluent with the low over that southern continent (Ishtar) or kept separate? If it's confluent, that will break the circumpolar low, won't it? Is that "allowed"? Or would the low bend down south around it, like the low around Greenland on the Earth map in your tutorial? And what would that do to the nearby oceanic high?
Also, are there easterly (blowing east-to-west) winds around the extreme poles, then?

4. Crap, I think that I put that northern-hemisphere continental high in July when I meant to put it in January. (I was basing it off of the high over Greenland.) Would that make more sense? And thanks for catching it! And tame question about the low bending south around it applies, I guess.

Updated and prettified maps will follow.

[acrosome]

Here's the prettied-up currents:



Sorry it looks so busy; I used a brush of a set width to help me track my loops, to be sure I closed them. I tweaked the current around Imdr so that it gets hit by a warm current, not unlike Europe. Hopefully it'll have a mild climate despite being at 40-50 degrees latitude. I tweaked a few other things, too, like the cold current hitting Artemis; I'd like a large desert there. I sort of wanted western Beta to be less desert but it's looking like there's no way to avoid that.

My warm currents seem to hit clusters of islands and ramify a lot. (I'm basing that on Southeast Asia, Malaysia, Borneo, etc.) Well, that and the rule of thumb that cold currents tend to be more cohesive, whereas warm currents break up like that. I generally tried to put small currents in where they mattered, too.

Here are the north and south poles, to check that they make sense:

North:



South:



Having that large continent sitting just off the south pole does lead to odd stuff. The circumpolar current has to mix with the warm water from that southern oceanic gyre. So, no huge cohesive warm current hitting Ishtar- it'll be a very cold place. Good fishing grounds, though...

I can probably neaten up that southern subpolar current, though. The area would be analogous to Earth's north pole, with a lot of land nearby but not actually on the pole. In Earth's Arctic Ocean the Beaufort Gyre is displaced significantly off of the pole. I'll move some currents around at my south pole.

[Azélor]

There is a low pressure system south of Greenland because the water is much warmer. But it's high overland.

Polar easterlies do exist but Wikipedia says they are weak and irregular,

4. Crap, I think that I put that northern-hemisphere continental high in July when I meant to put it in January. (I was basing it off of the high over Greenland.) Would that make more sense?

Somewhat low in July.

My warm currents seem to hit clusters of islands and ramify a lot. (I'm basing that on Southeast Asia, Malaysia, Borneo, etc.) Well, that and the rule of thumb that cold currents tend to be more cohesive, whereas warm currents break up like that. I generally tried to put small currents in where they mattered, too.

My guess it that slows down the currents (with possible shallow waters).
Meaning warmer water in the region.
The water is pretty hot around Indonesia. But as hot as in the Red Sea.