Lyman I think the geomorphology of Mtddle Earth is more that of California than Europe though the Climate regime is further North- for example Umbar probably has the Climate of Ensenada,BC. The main reason I came to that is the Misty Mtns are much like the Sierra Nevada. In fact when I fist read LOTR I was in the John Muir Wilderness & saw the hike to the Pass literally & how the snow especially in Winter would get more intense w/elevation. also the describtion of Caradhras fit the Sierra though red rocked peaks were rare. The now dry- thanks to LA- Owens river could have been the Anduin though maybe the lower Colorado workes better.The idea that Rhun with it’s Salt Playa lake reenforced that. The main problem is that at the latitude sugessed the Anduin Valley would have been in a huge Rain shadow & quite Arid.