What characterizes the tropopause?

The tropopause is best characterized as the boundary between the troposphere and stratosphere. This layer acts as a transition zone between the two atmospheric layers. In the troposphere, which is the lowest layer of the atmosphere, weather phenomena such as clouds, precipitation, and storms occur due to its relatively high density and the presence of water vapor. In contrast, the stratosphere, which lies above the tropopause, contains the ozone layer and has a more stable climate with fewer weather systems.

This transition is significant; it represents a point where temperature ceases to decrease with altitude, which is a defining feature of the tropopause. Above this boundary, the temperature tends to increase with altitude in the stratosphere due to the absorption of ultraviolet radiation by ozone. Understanding the role of the tropopause is crucial for meteorology and aviation, as it influences weather patterns and flight operations.

While the tropopause does dictate the limits of weather activity—meaning weather phenomena are generally less intense above this layer—the primary characteristic is its function as a boundary. It's also important to note that while there may be variations in humidity within the atmosphere, the tropopause itself is not defined by having a high concentration of water vapor.