Thunderstorms
Brazil

ANVIL
Solar heating of the Earth's surface heats the lower atmosphere. This heat can form a thermal updraft, and in the right circumstances a thunderstorm develops. The flat cloud structure seen here forms when thunderstorms reach the base of the stratosphere at roughly 13,500 meters. There it encounters a temperature inversion (the tropopause) and becomes neutrally buoyant and spreads out laterally.
UPDRAFT
This small domical cloud on the top of the anvil forms when the powerful updraft of the thunderstorm overshoots the tropopause.