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Convection in Thunderstorms
Building Atmospheric Giants
The up and down motions associated with convection help fuel monstrous thunderstorms. A thunderstorm feeds off of warm air underneath it. Warm air near the ground rises because it's less dense. When the air reaches the base of the cloud, water vapor in the air condenses and builds onto the cloud. When the water vapor condenses it releases some heat, which warms the air around it. This air now rises because it's less dense, and the process continues again and again. The air inside of a cloud continuously rises and falls, similar to a pot of boiling water. The cloud continues to build on itself until it reaches the tropopause, the point 10 - 12 kilometers above the ground where the atmosphere becomes stable. The tropopause acts like a lid, and forces the cloud to spread out at the top. This is why thunderstorms sometimes have an anvil shape. The thunderstorm will continue to grow as long as has a source of warm air underneath it. Once the supply of warm air is cut off, such as when falling rain cools the air under the cloud, the massive cloud will dissipate.