Troposphere
The troposphere is the lowest atmospheric layer, where temperature generally decreases with altitude and most weather occurs.
Environmental lapse rate: The rate at which atmospheric temperature changes with altitude at a particular place and time. Its usual decrease with height gives the troposphere its defining thermal pattern.
Atmosphere: A layer of gases surrounding a celestial body and held by gravity. The troposphere is the lowest part of this larger gaseous envelope.
Weather forecasting: The use of observations and models to predict future atmospheric conditions. Forecasts depend on tracking tropospheric winds, moisture, temperature, and pressure.
Tropospheric ozone: Ozone in the troposphere, formed through sunlight-driven reactions involving nitrogen oxides and volatile organic compounds. Unlike protective stratospheric ozone, it is a pollutant that harms health and vegetation.
Convection: Heat transfer through the movement of fluids, including rising warm air and sinking cool air. Uneven heating drives vertical motion that forms clouds and redistributes heat.
Atmospheric pressure: The force per unit area exerted by the weight and motion of gases in an atmosphere. Pressure falls with altitude, influencing air density and weather processes in this layer.
Numerical weather prediction: The use of computer models that solve equations of atmospheric motion to forecast weather. Models represent tropospheric processes to predict storms and evolving weather systems.
Photochemical smog: Air pollution produced when sunlight drives reactions among nitrogen oxides and organic compounds. Its ozone and other oxidants form in sunlit tropospheric air.
Atmospheric boundary layer: The lowest part of the troposphere, directly influenced by the underlying surface. Surface heating, friction, and moisture dominate this layer’s daily changes.
Water vapor: Water in its gaseous state, present in varying amounts in planetary atmospheres. Most atmospheric water vapor is concentrated here, enabling clouds and precipitation.