The troposphere is the lowest layer of the atmosphere. The troposphere extends from sea level to altitude of 18 km. Altitude is the height measured from sea level. However, the upper boundary of the troposphere varies with latitude and season. The upper boundary of the troposphere is called the tropopause.
The temperature in the troposphere decreases with altitude, which is the main characteristic of the troposphere. The troposphere is the densest layer of the atmosphere. About 99% of the atmosphere’s water vapor resides in the troposphere.
The temperature of the troposphere
In the troposphere, the temperature decreases with altitude. The temperature drops at a rate of 6.5° C per kilometer with increased altitude. The air is dense near the surface of the Earth, which absorbs the energy reflected by ground and ocean. Also, the absorption of infrared wavelengths is higher in the lower part of the troposphere. This is why temperature decreases with altitude in the troposphere.
Height of the troposphere
The height of the troposphere is not constant rather it varies with latitude and season. the upper boundary of the troposphere is called the tropopause. The altitude of tropopause depends on temperature. When the temperature in the troposphere increases with height, that height is assumed to be the upper limit of a troposphere. After the tropopause, the new layer begins called a stratosphere where temperature rises with height.
The tropopause at the equator is 18 km high, while near the pole it remains 8 Km. The graph above shows how the height of the tropopause changes with latitude. The tropopause height does not change gradually, rather it falls rapidly around at subtropical location.
Composition of the troposphere
The nitrogen and oxygen are the dominant gases in the troposphere. along with these, the troposphere contains carbon dioxide and other gases with small amounts. The troposphere also contains water vapor that is most important for clouds formation.
The tropospheric air also contains small dust particles or droplets that are called aerosols.
The common questions related to the troposphere
How is the height of tropopause determined?
In the troposphere, the air gets colder with height. But when we reach the tropopause then the air starts heating up. At this height, where the temperature starts to rise, it is considered the height of the tropopause.
Why do jet planes fly over the troposphere?
In the troposphere, air density is high. Most of the weather phenomena such as thunderstorms, cyclones, heavy clouds, and rainfall occur within the troposphere. To avoid this resistance the Aviator of a jet airplane often avoids flying in the troposphere.