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convert}}, far above all three layers.)
Earth atmosphere diagram showing the exosphere and other layers. The layers are to scale. From Earth's surface to the top of the stratosphere (50km) is just under 1% of Earth's radius.

The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and 99% of its water vapor and aerosols.<ref>McGraw-Hill Concise Encyclopedia of Science & Technology. (1984). Troposphere. "It contains about four-fifths of the mass of the whole atmosphere."</ref> The average depth of the troposphere is approximately {{safesubst:#invoke:convert|convert}} in the middle latitudes. It is deeper in the tropics, up to {{safesubst:#invoke:convert|convert}}, and shallower near the polar regions, approximately {{safesubst:#invoke:convert|convert}} in winter. The lowest part of the troposphere, where friction with the Earth's surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to {{safesubst:#invoke:convert|convert}} deep depending on the landform and time of day. The border between the troposphere and stratosphere, called the tropopause, is a temperature inversion.<ref name="DLA">Danielson, Levin, and Abrams, Meteorology, McGraw Hill, 2003</ref>

The word troposphere derives from the Greek: tropos{{#invoke:Category handler|main}} for "change" reflecting the fact that turbulent mixing plays an important role in the troposphere's structure and behaviour. Most of the phenomena we associate with day-to-day weather occur in the troposphere.<ref name="DLA"/>

Troposphere sections
Intro  Pressure and temperature structure  Atmospheric flow  Synoptic scale observations and concepts   See also   References  External links  

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