The stratosphere is the second layer of the Earths atmosphere, located above the troposphere and below the mesosphere. It is characterized by a highly stable temperature gradient that cools from top to bottom, with temperatures increasing with altitude due to the presence of the ozone layer, which absorbs and scatters ultraviolet (UV) radiation from the Sun, serving as a protective shield for life on Earth. The stratosphere is an atmospheric layer composed of a mixture of gases, including nitrogen, oxygen, and ozone. It is a region of intense interactions among radiative, dynamical, and chemical processes, in which the horizontal mixing of gaseous components proceeds much more rapidly than does vertical mixing. The overall circulation of the stratosphere is termed as Brewer-Dobson circulation, which is a single-celled circulation, spanning from the tropics up to the poles, consisting of the tropical upwelling of air from the tropical troposphere and the extra-tropical downwelling of air. The stratosphere is also a region where winds can far exceed those in the troposphere, reaching near 60 m/s (220 km/h; 130 mph) in the Southern polar vortex. The stratosphere is a layer of Earths atmosphere that is essential for life because it absorbs ultraviolet radiation.