Final answer:
The tropopause is the cold boundary between the troposphere and stratosphere, located at the top of the troposphere around 11-13 kilometers above the Earth's surface.
Step-by-step explanation:
The tropopause is the boundary between the troposphere and stratosphere. It signifies the transition from the lowest atmospheric layer, where temperature decreases with altitude, to the stratosphere, where temperature begins to increase due to the absorption of UV radiation by ozone. The tropopause is the coldest part of the atmosphere and marks the top of the troposphere, which extends from earth's surface up to an altitude of about 11-13 km (7-8 miles).