The upper atmosphere, 10 to 50 km above the surface, where a protective ozone layer forms.

An atmospheric layer between approximately 15 and 50 km above the Earth.

The layer of atmosphere that lies about 15 to 50 kilometres above the Earth's surface. In the stratosphere, the temperature rises with increasing height, which is the opposite of the situation in the lower atmosphere. Ozone occurs in minute quantities throughout the full depth of the atmosphere, but its concentration peaks within the stratosphere at an altitude of about 35 kilometres. This is referred to as the ozone layer. There is little up-and-down air movement in the stratosphere, so the ozone layer stays in position.

The region of the atmosphere immediately above the troposphere (q.v.). In the lower stratosphere temperature may continue to decrease with increase of height (but more slowly than in the troposphere) or may remain practically constant, or may increase with height. The transition front troposphere, to stratosphere, judged by change of temperature with height, is not always abrupt. At greater heights are other regions with special characteristics, e.g. the ozonosphere, where the concentration of ozone gas is greatest, centred at a height of about 20 miles; the ionosphere, the highly-electrically conducting region of ionised gases, extending upwards from the height of 50 or 60 miles. This region plays an important part in radio propagation. The main subdivisions of this region in order of increasing height are usually referred to as the D. E. (or Kennelly-Heaviside), F (or Appleton) regions or layers.