Troposphere

The troposphere is the lowest of the main layers of the Earth's atmosphere. The troposphere extends from Earth's surface to an average height of about 12 km.

The name "troposphere" is derived from the Greek tropos, meaning "turning." This reflects the fact that air within the troposphere commonly "overturns" or mixes from top to bottom. A vivid example of this overturning is the motions within a deep thundercloud, where air parcels near the Earth's surface often ascend to the top of the troposphere (called the tropopause).