With increasing altitude air temperature drops rapidly with increasing height, until a temperature of -55 degrees Celsius is reached at the top of the troposphere. The tropopause , extending from 11 to 20 kilometers, is an isothermal layer in the atmosphere where temperature remains constant over a distance of 9 kilometers. Above the tropopause, is the stratosphere which extends from 20 to 48 kilometers above the Earth's surface. In the stratosphere temperature increases with altitude because ozone gas found in this layer absorbs ultraviolet sunlight creating heat energy. Ozone is primarily found in the atmosphere at varying concentrations between the altitudes of 10 to 50 kilometers.
Ozone protects life from the harmful effects of ultraviolet radiation.
Without it life could not exist on Earth. Separating the mesosphere from the stratosphere is another isothermal layer called the stratopause . Above the mesosphere is another isothermal layer called the mesopause . The final atmospheric layer has an altitude greater than 90 kilometers and is called the thermosphere . The thermosphere is the hottest layer in the atmosphere as oxygen molecules absorb solar radiation.