Note how all the continents mirror the sides of Tamriel. Atmora is a frozen over hellhole as an exaggeration of Skyrim. Yokuda was a barely hospitable desert like Hammerfell. Pyandonea is a tropical rainforest like Valenwood and parts of Elsweyr. So logically Akavir must mirror the east of Tamriel. Judging by Morrowind, most of Vvardenfell is volcanic wasteland and marsh. Black Marsh is obviously marsh too. Thus, Akavir is mainly marshes. Disaster at Ionith mentions Akavir having rich, well watered fields, and that could've easily been marsh before Akaviri irrigation and whatnot. China has plenty of swamps, so a marshland Akavir would fit in with the Oriental stylings. Kamal is all frozen over, being an anomaly in this, but since Disaster at Ionith implies the Akaviri have weather magics, and since everyone hates the Kamal, I imagine that the Akaviri sorcerers intentionally froze the landscape to hinder the Kamal.