FIG. A-22. Atmospheric layering. Weather is mainly controlled by the troposphere. The jet stream at about 11 km involves a wave-shape course at midlatitudes. A circumpolar vortex extends sometimes to 60 km. Ionized layers in the ionosphere are important in radio transmissions. Atmospheric pressure falls off rapidly above the surface and is very small above 20 km. Temperature falls rapidly in the troposphere, is about 210–220 K in the stratosphere, and then rises to about 275 K at 50 km because of the absorption of 2100–2900 Å radiation by ozone.