20.6 The Atmosphere

20.6.2 Define the terms:

(a) troposphere;

The troposphere is the lowest layer of the atmosphere, extending from the Earth’s surface up to the tropopause.

It contains most of the atmosphere’s water vapour, cloud, and weather.

The depth of the troposphere varies with latitude and season, but is typically about:

• 26,000 ft near the poles
• 36,000 ft in the mid-latitudes
• 52,000 - 59,000 ft near the equator

Within the troposphere, temperature generally decreases with increasing altitude.

(b) tropopause;

The tropopause is the boundary between the troposphere and the stratosphere.

It marks the upper limit of most normal weather activity.

At the tropopause:

• The normal decrease of temperature with height largely stops.
• Temperature becomes nearly constant with height, or may begin to increase above it.
• Most cloud and weather are found below it.

The height of the tropopause varies:

• Lower near the poles
• Higher near the equator
• Generally higher in summer and lower in winter

Jet streams are commonly found near the tropopause.

(c) stratosphere.

The stratosphere is the layer of the atmosphere above the tropopause, extending upward to about 160,000 ft.