Description: Scattered visible light and microwave radar can used used to detect clouds and precipitation. Cloud formation in rising air can be simulated in the classroom by suddenly dropping the pressure in a glass chamber. The small cloud droplets formed in this way fall too slowly to ever reach the earth. There are two main mechanisms by which precipitation is generated from clouds. Collision coalescence occurs mainly over tropical oceans whereas the ice phase mechanism is more common and also more relevant to the practice of cloud seeding.