One side of a mountain is often rainy while the other side remains very dry. This dry area is called a "rain shadow." Mountains that are close to an ocean often have rain shadows. Air blows from the ocean to the mountains. When the air reaches the mountains, it must rise. As the air rises, it cools. Cool air cannot hold as much water as warm air can. So, as air rises over the mountains, it releases water as rain. On the other side of the mountain, the air falls and becomes warmer. The air has lost most of its water. There is little rain on the other side of the mountain.
Why does it rain as air passes over the mountain?
1. because air releases water as it cools
2. because the air falls and becomes warmer
3. because the mountain is close to the ocean
4. because two sides of a mountain are different
1. because air releases water as it cools
As the air rises over the mountain, it cools and cannot hold as much water vapor, so it releases the excess water as rain.