What atmospheric layer is closest to Earth's surface?

The troposphere is the atmospheric layer closest to Earth’s surface, extending from ground level up to about 8 to 15 kilometers (5 to 9 miles) in altitude, depending on geographic location and weather conditions. This layer contains most of the atmosphere's mass, including water vapor and aerosols, which are essential for weather phenomena.

In the troposphere, temperature generally decreases with altitude, which contributes to weather patterns and the formation of clouds. All human activities and life occur within this layer, making it critically important for our daily weather, climate, and overall environmental conditions.

The stratosphere, located above the troposphere, starts around 10 to 20 km and contains the ozone layer, which protects life on Earth from harmful ultraviolet radiation. The mesosphere lies above the stratosphere and is where temperatures begin to decrease with altitude again. Finally, the thermosphere is the highest layer mentioned, characterized by increasing temperatures due to solar activity, and it is situated far above the troposphere. Each of these upper layers serves different functions and plays distinct roles in Earth's atmosphere, but the troposphere is uniquely vital for weather and life as we know it.