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

The layer of the atmosphere that is closest to Earth's surface is the troposphere. This layer extends from the ground up to about 8 to 15 kilometers (5 to 9 miles) in altitude, depending on geographic location and weather conditions.

The troposphere is where all weather phenomena, such as clouds, rain, and storms, occur, due to the presence of water vapor and air movement. It is characterized by a decrease in temperature with increasing altitude. The troposphere is crucial for life on Earth because it contains the air we breathe and is integral to the overall climatic systems that support ecosystems and human activities.

Understanding the structure of the atmosphere is essential, especially for those in fields related to environmental science, meteorology, and HVAC, as it influences weather patterns and air quality, which are critical in various applications, including refrigerant management and compliance with regulations like those in the EPA 608 certification.