Why does the Great Basin region and Mojave desert east of the Sierra Nevada mountains gets less rainfall than the western side of the Sierra Nevada?

The Great Basin region and Mojave Desert receive less rainfall than the western side of the Sierra Nevada primarily due to the rain shadow effect. As moist air from the Pacific Ocean rises over the Sierra Nevada mountains, it cools and condenses, leading to precipitation on the western slopes. Once the air descends on the eastern side, it warms and loses its moisture, resulting in significantly drier conditions in the Great Basin and Mojave Desert. This topographic barrier thus creates a stark contrast in rainfall patterns between the two sides.