Which layer of the atmosphere is closest to the Earth's surface?

The troposphere is the layer of the atmosphere that is closest to the Earth's surface. It extends from the ground up to about 8 to 15 kilometers (5 to 9 miles) high, depending on geographic location and weather conditions. This layer contains most of the atmosphere's mass, including clouds and weather phenomena like rain, snow, and storms, making it critical for meteorology and climate.

Temperature generally decreases with altitude in the troposphere, which contributes to weather patterns and phenomena. The troposphere is also where we find the air we breathe, as well as most living organisms, making it essential for life on Earth. This proximity to the Earth's surface means that it contains the bulk of the atmosphere’s water vapor, which is an important component for weather systems.

Other layers of the atmosphere, such as the thermosphere, stratosphere, and mesosphere, are located above the troposphere, and they have different characteristics concerning temperature, pressure, and composition. Each of these layers plays a unique role in atmospheric science, but none are as directly involved in our day-to-day weather as the troposphere is.