Our lowest layer, where weather occurs. Height lowers temperature and air pressure.
Ozone protects against UV radiation from tropopause to 50 km. CFCs cause the "Antarctic ozone hole.
After stratosphere, mesosphere reaches -90°C at mesopause.
Absorption of solar energy raises mesosphere temperatures. Ionosphere over 80 km affects radio wave reflection and absorption.
Starting at 500 km, the exosphere has few oxygen and hydrogen atoms. Some escape into space; few collisions.
Charged particles produce Van Allen belts in Earth's magnetic field.
Earth's atmosphere weighs around 5×10^15 tonnes, or 1/200,000 of its total mass. Water-vapor-induced annual fluctuations.
the mean mass is 5.1480×10^18 kg, with slight yearly fluctuations due to water vapour.