Atmosphere of Earth However, polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest. The stratosphere is the highest layer that can be accessed by jet-powered aircraft. The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about , although this altitude varies from about at the geographic poles to at the Equator, with some variation due to weather. The troposphere is bounded above by the tropopause, a boundary marked in most places by a temperature inversion (i.e. a layer of
Computation of radiowave attenuation in the atmosphere recommendations is available for download and is available to the public. The document ITU-R P.676-8 of the ITU-R section considers the atmosphere as being divided into spherical homogeneous layers; each layer has a constant refraction index. By the use of trigonometry, a couple of formulas and an algorithm were derived. Through the use of an invariant, the same results can be directly derived: An incident ray at A under the angle Φ hits the layer B at the angle "θ". From basic Euclidean geometry: By Snell's law: so that Notes: The ITU recommended algorithm consists of launching a ray from