TROPOspheric

The troposphere is the lowest layer of Earth's atmosphere, extending from the surface up to the tropopause, the boundary with the stratosphere. It contains the majority of atmospheric mass and is where nearly all weather phenomena take place.

Its thickness varies by latitude and season, from roughly 8–12 km at mid-latitudes to about 16–18 km near the equator and lower near the poles. Temperature generally decreases with height at an average lapse rate of about 6.5°C per kilometer, giving a surface temperature around 14–15°C in mid-latitudes and frigid temperatures near the top.

Within the troposphere lies the planetary boundary layer at the surface, a region of active turbulence and mixing driven by surface heating, humidity, and roughness. Weather systems, clouds, rain, snow, and storms develop and evolve here as moisture and heat are transported vertically and horizontally.

Composition and chemistry: Water vapor is the most abundant greenhouse gas in this layer; carbon dioxide, methane, and nitrous oxide are also present. Ozone in the troposphere is produced photochemically and acts as a pollutant and greenhouse gas; in contrast, the protective stratospheric ozone layer resides above the troposphere. Aerosols and particulates influence radiation and cloud formation, affecting climate and air quality.

Boundary with the stratosphere occurs at the tropopause, whose altitude depends on latitude and season; the tropopause acts as a barrier for most convection. The term tropospheric is used to describe anything pertaining to this layer, such as tropospheric winds, tropospheric ozone, or tropospheric humidity.