WIP Climate Help, Please

[acrosome]

Howdy, all. I have a long-term project mapping a terraformed Venus. Everything in that link is obsolete, though, so just look below, but it will answer questions about rotation, axial tilt, etc. (Basically, you can assume that the planet is now Earth-like, with a 24-hour day, a 20-degree or so axial tilt, and the sun rises in the east.) I have been using the method of Azelor, and Azurewings' script. Maps follow, with my questions at the bottom.

First, the topographic overview:





Temperatures:





Precipitation:





The climate output:





These temperature and precipitation maps are crude first approximation products- I intend to do some smoothing. But before I get too far into that I have some questions.

1. That large desert in Artemis... should it cut all the way to the east coast? I modeled that area on China and southern Asia, which gets quite a bit of precipitation, but unlike China there really is no mountain range to stop the desert.

2. Mountain rain-shadows are giving me fits. I tried to model the mountains themselves by dropping their precipitation, but in particular those very high mountains on Atlu and Ishtar should probably have rainshadows. I suspect that mine are not the right size, or dryness. I'm alsop not so sure about the scattered high (but much more isolated) peaks on Thetis and Ovda.

And of course, ANY other input is quite welcome. I do ok with temperature maps but in particular I suck at precipitation maps.

[AzureWings]

Just my two cents, as someone who also struggles with making satisfactory-feeling precipitation maps:

Do you have a map with wind contours drawn on it for the updated version of the project? Precipitation decisions really depend on how you've decided the winds work out. For example, whether that desert in Artemis reaches the east coast depends on whether the east coast has a source of precipitation like being the receiver of a wind pattern originating in warm waters (and then depending on the direction of that wind the question is to what extent do factors prevent that water from reaching the desert portion, such as it being more tangential to the coastline and missing the desert region or the water all raining out before it gets to the desert). Mountain ranges don't generally stop deserts as far as I know; they're more likely to cause them (though they aren't the only possible cause) due to rain shadow effects causing water not to reach the desert side depending on wind directions. If there is any wind coming off warm waters reaching that east coast before other large land areas it should be seeing that precipitation. If the wind patterns from water bodies "miss" that area during a given season, or come overland through other areas that see precipitation from it before reaching that area, it should be drier. Given your desert positioning I'm assuming that region's centered on around 30N latitude; note that both the Sahara and Florida are around the same latitude but the latter gets wind off the Atlantic and varying pressure systems and the former has a high pressure system that stays mostly in place and gets most of its wind coming from the northeast (with mostly land in that direction). That's from some brief research but I'm not really knowledgeable about the complexities involved in those systems. As an overall summary, if the east coast of Artemis is getting wind coming from the ocean to the east it should be wet, like China getting wind off the Pacific; if its prevailing winds are coming from the west across the desert it should almost definitely be dry (and of course those statements apply for individual seasons if the wind patterns change over the course of the year).

When looking at rain shadows, it's not that the mountains are dry specifically; it's that on the rising slopes more water falls due to orographic lifting and then there isn't as much moisture left in the air by the time it reaches the other side. Mountains that exhibit strong rain-shadow effects probably have increased precipitation on one side and decreased on the other. Azélor's tutorial talks about orographic lifting increasing precipitation; just remember that anytime you increase the precipitation of an area due to elevation any area whose precipitation is fed by the same airstream further on has lost that extra precipitation that fell there. The more you increase the precipitation on the side water-bearing air is incident on, the more you should decrease it past that point.

[acrosome]

Yes, I generally understand all of that. Frankly, my precipitation woes stem, I think, from not having too much confidence in my wind maps, so I tend to look at real-world examples that are similar when I am unsure. Like China for eastern Artemis. So for instance (with lat/long):





I worked these out through Azelor's tutorial, and you can see that wind tends to avoid eastern Artermis in January... but I have come to doubt that it would really work that way. I think that I didn't quite do winds correctly. I didn't have a good grasp of how large a landmass had to be to cause a high pressure zone, and looking at real Earth examples wasn't much help, since it seemed to vary considerably. Or maybe I'm wrong and I should tone down the January precipitation and just rely on those July winds for precipitation. I may try that and see how it works.

I understand orographic lift and (generally) rainshadows, too. Orographic lift is what I was referring to when I mentioned mountains that "stop" a desert- like the Ethiopian Highlands do- since that was how Azelor referred to it too. But where I fail is understanding just how profound the effect is for a given mountain. The Olympics are big enough that Sequim doesn't get as much rain as the west of the Washington Coast, but the Himalayas cause the Gobi Desert. There is a difference in scale, there. So I'm trying to figure out exactly how large and dry these rainshadows should be. And also, since I think my wind maps aren't quite perfect, in which direction.



Oddly, I tend to be more confident about my currents...

And just because I think it's a thing of beauty I'm going to post this, too: