Mesosphere

The mesosphere (from the Greek μέση, Mese "center" and σφαίρα, sphaira " ball " ) is the average of the five layers of the atmosphere and part of the ionosphere and homosphere.

It is bounded to the earth by the stratopause ( about 50 km altitude) of the stratosphere and upward through the mesopause ( at 80 to 90 km altitude) of the thermosphere. Because of this extremely thinned air, and the fact that hardly any more ozone is present and the absorption of high-energy UV radiation in the stratosphere takes place, the temperature drops from about 0 ° C at the stratopause with seasonal fluctuations on average about -90 ° C in about 80 kilometers altitude. The temperature decrease is approximately 3 K / km, however, considerably lower than that in the troposphere.

So the mesosphere extends from about 50 km up to an altitude of about 85 km. She is known as the cold layer, since the temperature and air pressure drop dramatically. Since this sphere is above the ozone layer, the UV light is so strong that a human body would be contracted within a very short time severe burns. Above her is the mesopause. Thereafter, the temperature remains constant and only increases again in the thermosphere strongly again - depending on solar activity - up to 2,000 ° C at. In the mesosphere circulation of summer and Winterpol that causes an upward transport of air masses in the range of Sommerpols and a downward transport in the area of ​​Winterpols exists. Due to the associated adiabatic cooling and heating of the air in the summer is the mesosphere significantly (about 130 to 150 K) cooler than in the winter.

The chemical composition of the mesosphere is fairly constant, as in the troposphere and stratosphere. Their major constituents are nitrogen, oxygen, argon and carbon dioxide. The mesosphere thus belongs to homosphere. When meteors fall to the earth, they usually burn up in the mesosphere (see meteor ).

In the upper mesosphere, the polar ice caps to form the noctilucent clouds, which are bluish - silver shimmer visible to the naked eye in our latitudes, if they reflect the light of the setting sun. It is believed to be accumulations of ice particles, which therefore should not be confused with the North or northern lights, but not with the polar stratospheric clouds.