If there was a supermassive structure built on earth (30km tall, 10km wide/deep tower with slightly slanted faces), what sort of effects would this cause on the surrounding areas? Specifically, what effect would this have on clouds, wind, and precipitation? What are the effects of a shadow this size on surrounding ecosystems? Could it be possible to create an entirely new “vertical” biome on the faces of this structure?
Let's put this in perspective here:
30km is 30,000 meters.
There are 14 mountains in the Himalayas that are over 8,000 meters. Your building is insanely high. If you are talking about having some kind of vertical biome it would have to be enclosed. Just think of what kind of life lives at the peaks of the highest Himalayan mountains. Exactly. And that's not even up to one third of the height of your megastructure. So I would say having a vertical biome on the faces of the structure might only be possible at lower elevations in the bottom fourth of the building. Then you would have to have a way to change the atmospheric pressure inside and oxygen levels inside the building also. But that's not your question.
Environmental/Meteorological effects. There would be a massive shadow, for sure. Also depends which hemisphere your building is in. Let's assume it's the north. Then the northern side of the building will have shorter vegetation, moss, lichen, due to less sunlight. It'll be colder, snow will stay on the ground longer. 10,000 meters of shadow is pretty significant.
There sheer size of the building could break up cloud formations.. may form heavy condensation (?) on the sides of the building. Of course one side could be protected from prevalent winds come from a specific direction, but that would be more apparent the closer the location to the building.
It will be windy around the tower.
Might be more precipitation as clouds will be forced up along the walls. You might get hail, or maybe even avalanches from ice that forms high up on the tower.
The massive shadow will stunt plant growth, but only at a short distance since motion of sun will still provide almost the same amount of sunlight to places only a few km from the tower.
Vertical biome assumes there are cracks and holes for plants and animals to live in. But that means that the tower material is weathering, so it will collapse pretty soon (maybe couple hundred years). If somebody is maintaining the tower, they will keep all life off it. If you really want biome on it, have it made from indestructible material, but with nooks and crannies to accommodate living things.
Edit: you have to think about how this thing was built. If it was built from local materials, there will probably be a good sized lake (or a few missing mountains) nearby. The weight of it might push the entire area down. And you will need some super-strong materials, or hydrogen balloons to deal with weight.
you may have something like a Chinook effect similar to Alberta depending on the geography. For those who don't know a Chinook is when moist air from off the coast gets pushed uphill losing temperature and thus its water carrying potential raining/snowing on the coastal side of the vertical climb and when descending the far side of the slope the air is much warmer and drier. This isn't the most scientific explanation and will update this later.