The stratosphere (/ˈstrætəˌsfɪər, -t-/) is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere.[3][4] The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air high in the sky and the cool layers of air in the low sky, close to the planetary surface of the Earth. The increase of temperature with altitude is a result of the absorption of the Sun's ultraviolet (UV) radiation by the ozone layer.[5] The temperature inversion is in contrast to the troposphere, near the Earth's surface, where temperature decreases with altitude.

Space Shuttle Endeavour appears to straddle the stratosphere and mesosphere in this 2010 photo. "The orange layer is the troposphere, where all of the weather and clouds are generated and contained. This orange layer gives way to the whitish Stratosphere and then into the Mesosphere."[1] (The shuttle is actually orbiting at more than 320 km (200 mi) in altitude, far above this transition layer.)
This image shows the temperature trend in the lower stratosphere as measured by a series of satellite-based instruments between January 1979 and December 2005. The lower stratosphere is centered around 18 kilometers above Earth's surface. The stratosphere image is dominated by blues and greens, which indicates a cooling over time.[2]
Diagram showing the five primary layers of the Earth's atmosphere: exosphere, thermosphere, mesosphere, stratosphere, and troposphere. The layers are to scale. From Earth's surface to the top of the stratosphere (50 km) is just under 1% of Earth's radius.

Between the troposphere and stratosphere is the tropopause border that demarcates the beginning of the temperature inversion. Near the equator, the lower edge of the stratosphere is as high as 20 km (66,000 ft; 12 mi), at midlatitudes around 10 km (33,000 ft; 6.2 mi), and at the poles about 7 km (23,000 ft; 4.3 mi).[5] Temperatures range from an average of −51 °C (−60 °F; 220 K) near the tropopause to an average of −15 °C (5.0 °F; 260 K) near the mesosphere.[6] Stratospheric temperatures also vary within the stratosphere as the seasons change, reaching particularly low temperatures in the polar night (winter).[7] Winds in the stratosphere can far exceed those in the troposphere, reaching near 60 m/s (220 km/h; 130 mph) in the Southern polar vortex.[7]

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