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StratosphereEdit

The stratosphere is the second major layer of Earth’s atmosphere, lying above the turbulent, weather-driven troposphere and below the mesosphere. It extends roughly from about 10–15 kilometers above the planet’s surface near the poles to about 50 kilometers at higher latitudes and around the equator. Unlike the troposphere, where convection drives weather systems and mixing, the stratosphere is comparatively stable, with far fewer weather processes and very little vertical mixing. A defining feature is the presence of the ozone layer, a region where ozone (O3) concentrates and absorbs a significant portion of the Sun’s ultraviolet radiation, shaping both the chemistry of the layer and the amount of UV radiation that reaches the surface.

Because of its relative calm and its role in shielding life from harmful ultraviolet light, the stratosphere has been a focus of scientific study and technological use. It supports long-range, high-altitude flights, weather balloon research, and satellite-based observations that inform climate and atmospheric science. The scientific record on the stratosphere includes robust explanations of its structure, chemistry, and dynamics, as well as ongoing debates about how human activities influence stratospheric chemistry and climate.

Structure and boundaries

  • The lower boundary of the stratosphere is the tropopause, where the temperature stops decreasing with height and begins to rise. The tropopause marks the transition from the troposphere to the stratosphere and shifts with latitude and season. See tropopause.
  • The upper boundary is the stratopause, where temperatures stop increasing with altitude and start to fall again as one moves into the mesosphere. See stratopause.
  • The vertical extent of the stratosphere varies with latitude and season, but it commonly spans about 10–50 kilometers above the Earth’s surface.
  • Temperature in the stratosphere generally increases with altitude, a reversal of the tropospheric pattern. This inversion is driven largely by the absorption of ultraviolet radiation by ozone, a process that warms the surrounding air.

Thermal and chemical structure

  • The temperature rise with height in the stratosphere (the thermal inversion) is intimately tied to ozone chemistry. Ozone absorbs UV radiation, converting it into heat and creating a stable layer that inhibits vertical mixing.
  • The ozone layer resides primarily in the lower to middle stratosphere, where ozone concentrations are highest and UV absorption is most intense. See ozone layer.
  • Stratospheric chemistry is shaped by interactions among ozone, oxygen, and various trace gases. These reactions determine ozone production, loss, and transport within the layer. Relevant topics include ozone depletion and related atmospheric chemistry.
  • The overall chemical balance in the stratosphere is influenced by natural processes (solar radiation, volcanic aerosols, meteor injections) and human-produced substances that reach the upper atmosphere, such as chlorinated and brominated compounds. See chlorofluorocarbons and ozone depletion.

Dynamics and transport

  • The stratosphere is more stable than the troposphere, which means less vertical mixing. This stability helps isolate stratospheric chemistry and allows long-range transport patterns to develop.
  • A principal large-scale circulation in the stratosphere is the Brewer–Dobson circulation, which describes the slow ascent of air in the tropics, poleward transport in the stratosphere, and descent in higher latitudes. See Brewer–Dobson circulation.
  • Polar vortices are strong, persistent cyclonic circulations that form in winter and can influence stratospheric temperature and composition. When disrupted, they contribute to events such as stratospheric sudden warmings, which have downstream effects on weather patterns. See polar vortex and stratospheric sudden warming.
  • Volcanic eruptions and other atmospheric disturbances can inject aerosols into the stratosphere, where they can persist for months to years and alter radiation balance and chemistry. See volcanic aerosol.

Ozone layer and UV protection

  • The ozone layer acts as a shield, absorbing the majority of the Sun’s damaging ultraviolet radiation. This protective effect is critical for reducing the risk of skin cancer, cataracts, and harmful impacts on ecosystems.
  • Human activities that release ozone-depleting substances into the atmosphere have historically reduced ozone concentrations in the stratosphere, leading to international policy responses. See ozone depletion and Montreal Protocol.
  • The discovery of the ozone hole over Antarctica in the 1980s highlighted the vulnerability of the stratosphere to anthropogenic emissions and spurred regulatory action. The science and policy implications are discussed in sources on ozone layer, Montreal Protocol, and related topics.

Human interactions and technology

  • Stratospheric aviation takes advantage of the stable, low-turbulence environment at high altitudes for certain types of research aircraft and long-range flights.
  • Stratospheric balloons and satellites enable measurements of atmospheric composition, temperature, wind, and radiation, contributing to climate models and weather prediction.
  • Policy debates have centered on the balance between environmental protection (such as preserving the ozone layer) and economic activity. The history of regulation, innovation, and international cooperation around ozone-depleting substances is a notable case study in environmental policy. See Montreal Protocol and chlorofluorocarbons.

Measurement, observation, and research

  • Remote sensing from satellites provides global views of ozone concentration, temperature, and chemical tracers in the stratosphere. See satellite technologies relevant to atmospheric science.
  • In situ measurements are obtained through radiosondes, aircraft campaigns, and balloon-borne instruments. See radiosonde for a common atmospheric profiling tool.
  • Ground-based and airborne lidars, spectrometers, and other instruments complement satellite data to build a comprehensive picture of stratospheric chemistry and dynamics. See lidar and spectroscopy for related methods.

See also