| Troposphere | Structure of the Earth's Atmosphere : Troposphere |
Troposphere The troposphere is the atmospheric layer closest to the planet and contains the largest percentage of the mass of the total atmosphere. It is characterized by the density of its air and an average temperature decrease with height ( lapse rate ) of 6 oC per kilometer.
Temperature and water vapour content in the troposphere decrease rapidly with altitude. Water vapour plays a major role in regulating air temperature because it absorbs solar energy and thermal radiation from the planet's surface. The troposphere contains 99 % of the water vapour in the atmosphere. Water vapour concentrations vary with latitudinal position(i.e. North to South). They are greatest above the tropics, where they may be as high as 3 %, and decrease toward the polar regions.
All weather phenomena occur within the troposphere, although turbulence may extend into the lower portion of the stratosphere. Troposphere means "region of mixing" and is so named because of vigorous convective air currents within the layer.
The boundary between the troposphere, and the stratosphere is called the tropopause. The height of the tropopause from the ground ranges from 8 km in high latitudes, to 18 km above the equator. Its height also varies with the seasons; highest in the summer and lowest in the winter. Air temperature within the tropopause remains constant with increasing altitude. The tropopause is a boundary layer defined by a sudden change in lapse rate.
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