Rheia: one final try at ground-up worldbuilding

[Naima]

Alright, now for precipitation, which is probably the part I'm least confident about overall. Unfortunately it also seems to be the area where ExoPlaSim makes the most noticeable systematic errors, so while it's certainly useful comparing the outputs there's definitely lots of room for interpretation here. Below are my first passes at precipitation maps, along with ExoPlaSim's outputs. Note that I didn't take into account orographic lift yet for my July map, as MrBragg sent me the ExoPlaSim results for Rheia before I got to that and I wasn't patient enough to wait.

Rheia_precipitation_jan.pngRheia_precipitation_jul.pngpr_in_rheia01_av10_jan.pngpr_in_rheia01_av10_jul.png

Phew, alright, some noticeable differences there. Specifically:

1. ExoPlaSim moves the ICTZ much less, keeping peak precipitation mostly near the equator regardless of the season. Others have noticed this as well (see: MrBragg's results in his thread, Nikolai's results in the Pasta tutorial I linked in my last post), and it means that equatorial areas are wetter than otherwise expected, and subtropics are much dryer. It seems to be less about pressure systems (which in general I agree with), and more about how it models precipitation and maybe winds. I suspect this has something to do with the lack of currents in the model: onshore winds that pass over warm currents seem to drive the particularly heavy monsoon rains. Still, I'm not sure in general. Whatever the reason, I'm electing to keep my rainiest areas around the ICTZ, rather than right along the equator as ExoPlaSim calls for. On the other hand, I definitely moved my ICTZ a little bit too far in some spots, so I'm moving my heaviest rains equatorward in some spots.

2. ExoPlaSim seems to do a surprisingly good job of modeling lee cyclogenesis (winds passing perpendicular to mountain ranges create some precipitation on the leeward side), and it caught some areas that I missed. I'm including those, and it's an impressive bit of modeling, assuming that's what it's really catching.

3. On the same token it does a pretty good job of modeling the rainshadow effect, modelling leeward areas of mountains as being fairly dry. In some spots I think it might even overstate the effect a little, especially near the ITCZ, but in general it's helped catch some spots I missed.

4.Unsurprisingly, ExoPlaSim doesn't really model the effects of cold currents that make areas east of high-pressure areas particularly dry (think: Atacama and Kalahari Desert), meaning that some areas are wetter than I'd put in. I'm keeping those dry where there's wind blowing off of a cold current from a subtropical high.

5. In addition to the monsoon, ExoPlaSim also seems to underestimate the extratropical storm paths to the west of the subtropical ridge, making east coasts somewhat dryer than they really are; on Earth this shows up as making the southeastern US mediterranean climates and making Japan a little dryer than it should be as well. I probably overstated this effect a little bit in my map so I'm making my east coasts a little dryer, but not as dry as ExoPlaSim calls for.

6. In general it models continental interiors as somewhat drier than what I put; in part this might be due to understating the impact of some of the effects I mentioned above like monsoons and extratropical storms, and this is probably why it modeled Rheia's continental interiors as being blisteringly hot. On the other hand I think I was underestimating the extent to which moist winds would be blocked by all my coastal mountain ranges. Again, I'm making things a little dryer, but not making them into the blast furnaces ExoPlaSim is modeling.

I also just went through and made some other random adjustments where my initial maps differed from the ExoPlaSim model, generally assuming the model was more correct than I was. Here are my revised precipitation maps:

Rheia_precipitation_jan_revised.pngRheia_precipitation_jul_revised.png

I'll leave this here for now, as now I need to figure out how to run the scripts from the Azelor tutorial... did them once already but that was a VERY long time ago. Will make another post when I have my complete climate maps. Anyway, as always comments and corrections are very welcome!

Great job. Though don't stress too much because to have a more precise calculation of climate simulation the tools should also take into account : thermohaline circulation, volcanic activity, solar flares , strenght of solar luminance, albedo reflection , possible meteoric impacts, biological activity density, axial tilt and planet orbit , greenhouse gases densities, in particular co2 concentration, carbon dioxide levels absorbed by oceans relative to its mass, vegetation land cover ... when co2 gradually drops overall it allows the climate to cool, with some ups and downs. Once carbon dioxide concentrations becames low enough (around 300 parts per million) , the ice age cycle begins.
Its all far to complex to take track in precise simulation I think so any good informed guess is more than accurate to me.

[MrBragg]

thermohaline circulation, volcanic activity, solar flares , strenght of solar luminance, albedo reflection , possible meteoric impacts, biological activity density, axial tilt and planet orbit , greenhouse gases densities, in particular co2 concentration, carbon dioxide levels absorbed by oceans relative to its mass, vegetation land cover

A number of these actually are taken into account during the simulation. Solar flux (and star temp), albedo of different land types, vegetation cover, obliquity / eccentricity, and gas concentrations / pressures are all treated. There are certainly simplifications and systematic errors in the model outputs, but in terms of variables that get treated it does quite a thorough job and allows the effects of any one of these variables to be isolated and varied.

[Naima]

A number of these actually are taken into account during the simulation. Solar flux (and star temp), albedo of different land types, vegetation cover, obliquity / eccentricity, and gas concentrations / pressures are all treated. There are certainly simplifications and systematic errors in the model outputs, but in terms of variables that get treated it does quite a thorough job and allows the effects of any one of these variables to be isolated and varied.

Nice then could be an alteration of those parameters that gives abnormal temperatures on continents like I read before?

[MrBragg]

Nice then could be an alteration of those parameters that gives abnormal temperatures on continents like I read before?

When I ran the simulation for Rheia I kept all of the parameters identical to Earth's except for the heightmap. ExoPlaSim consistently seems to overestimate temperatures--it does so by several degrees for Nikolai's baseline earth model--and I had to drop the CO2 levels by >50% to get more reasonable temperatures for my simulations. I could do that here, too, though Tiluchi seems to have already done a really nice job of hybridizing the ExoPlaSim results with their intuition.