I'm really interested in using a tidally locked planet as the setting for a new fantasy piece of mine. Here's what I have so far: The only habitable area would be the twilight zone (hehe). The dark side would be completely frozen over, with a dense atmosphere. The sunny side would be like Utah, or the Sahara with a thin atmosphere. Due to one side of the planet being hot and the other cold, there would be fierce storms, and all wind would be warm because of the high pressure air moving to the low pressure air. I have a feeling the sunny side would be full of gigantic mountains and valleys because the water that would normally be covering them would be evaporated. Due to the massive ammounts of evaporated water, there'd be a LOT of cloud cover. Would it rain all the time? it would probably be very humid. Anyways, these are my thoughts about it. Any insights would be greatly appreciated. Also, assume that the planet is about twice as big as Earth, and that the distance and size relative to its sun are the same ratio of Earth to our sun. Basically, its another Earth that happens to be tidally locked to its sun. Thank you for any response!
Tidal locking could render habitable planets inhospitable has a pretty thorough description of what you want. Here's another with a quick summary of winds, evaporation and erosion.
An author I enjoy muchly, Robert J. Sawyer, has a series called the Quintaglio Ascension that takes place on a tidally locked world and makes much use of this fact as a plot driver. In the real world, without any sci-fi glossing of truths, a tidally locked world would probably be a very seismic place. There are ever-present tidal differences between the near side and the far side of the sphere.
There is much debate among astronomers about the habitability of tidally locked worlds. My impression is that basically we don't know what they are like. I do think a significant difference in air pressure between the day and night sides is unlikely. Global winds would equalize the pressure pretty well. It has been thought that, in some cases at least, the night side would get so cold the atmosphere would freeze onto the surface, eventually creating a planet with no atmosphere. My understanding is that computer models of tidally locked worlds suggest the reality is likely more complex. I'm actually working (slowly) on a story that takes place on a tidally locked world. My interest is in all the little things we don't think about living on a planet like the Earth. For example buildings would cast unmoving shadows making the shadows themselves part of the landscaping. The daily rhythms we take for granted (sleep during the night, awake during the day) would either not exist or be tied to different cycles. In my story the natives are intelligent but they have an instinctual fear of darkness because their species evolved in a world where the sun never sets. Their astronomy and artificial lighting technology is relatively backward (who needs artificial lights when the sun is always up?). They design their cities so the buildings don't cast shadows on each other, affecting their architecture. The never ending daylight permeates their entire biology, culture, technology, and religious beliefs. The complexities of capturing such a world begin with the physical nature of it but definitely don't end there. Good luck!