Answer: Rain shadow
Step-by-step explanation:
This relates to frontal rainfall. With frontal rainfall, warm and moist air is made to rise up due to the incline of the mountain and as it reaches higher areas, it condenses and forms clouds which then fall as rain.
This air will no longer be warm or moist and so will no longer be able to induce rainfall and as it sinks to the opposite side of the mountain, it forms a rain shadow which is an area that does not get much rain because the rain has already fallen on the other side.