This is a diagram showing relief rainfall. Hot, moist air rises as it approaches the mountain, cooling and producing rain. Once it is cold, this air is denser, and so moves back towards the warm air above the ocean. This happens because the warm air is less dense; air will always move from areas of high density to low density. Once back above the ocean, the air moistens and warms again, continuing the cycle. This movement of air causes breezes.