Stratosphere
Stratosphere, upper layer of the atmosphere commencing at an altitude of 8 to 16 km (5 to 10 mi) and extending upward to about 50 km (30 mi). In the lower portion of the stratosphere, the temperature remains nearly constant with height, but in the upper portion the temperature increases rapidly with height because of absorption of sunlight by ozone. The stratosphere is almost completely free of clouds or other forms of weather.