Weather in a 5 mile deep crater

I've done a fair bit of research to come up with this scenario. I hope it's not "too broad" to ask for a reality check. Have I overlooked anything? Does it all sound plausible?

My world takes place in a massive crater, the only habitable place left on the planet. It is roughly 800 x 600 miles and 5 miles deep. At the bottom it is 1.2 atm in pressure, while the surface is at 0.5 atm.

Due to the extreme "altitude" conditions the surface of the planet is cold (would it really be though?) windy, and home to extremophile bacteria mats/mounds, and possibly lichens/moss. The wind here is extremely fast because there's not much to slow it down.

The sides of the crater are gently sloping downwards, and the wind follows it down. The bacterial mats slowly give way to montane grassland and meadows. Early morning dew from the cold winds is the source of water here. Small gnarled trees grow slowly and are warped by the wind. Meadows are nearby springs, where ancient aquifers were fractured during the meteor impact.

Next comes the treeline and the coniferous forests with fern undergrowth. The wind is slowed by both the trees and its compression at -12,000 feet into the crater. Rain occasionally falls here if the conditions are right. Overall the precipitation is mostly occult. This area has sizable lakes from other meteor impacts which are filled by fractured aquifers and streams from up the crater.

Eventually the heat of the Earth warms the cool air and we reach temperate deciduous forests. Winds are breezy here and carry precipitation from higher up the crater. Evening showers are relatively common. Streams have become rivers by this point. The forests reach all the way to sea level, except where humans have cleared them away for agriculture.

A massive sea covers much of the bottom of the crater, and fortunately it has reached an equilibrium between evaporation and being filled from the aquifers.

In the sea are a series of islands from the complex crater. These islands experience hot moist air, daily rain, and are temperate rainforests. It is here, finally, that the air rises up in a massive updraft. The hot air rises, disperses, and mixes with the atmosphere. Some water vapor finds its way back into the crater, but much more leaves.

I know it's a big task, but does this all sound plausible? Is there anything I've missed or greatly overlooked?

posted about 6 years ago

Hippeus_Lancer‭

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