Radio atmospheric In the case of the ionospheric D-layer, it depends, in addition, on time of day, season, latitude, and the geomagnetic field in a complicated manner. VLF propagation within the Earth–ionosphere waveguide can be described by ray theory and by wave theory. When distances are less than about 500 km (depending on frequency), then ray theory is appropriate. The ground wave and the first hop (or sky) wave reflected at the ionospheric D layer interfere with each other. At distances greater than about 500 km, sky waves reflected several times at the ionosphere must be added. Therefore, mode theory is here
Atmospheric wave scale Rossby waves gives rise to sudden stratospheric warmings and the deposition by gravity waves gives rise to the quasi-biennial oscillation. In the mathematical description of atmospheric waves, spherical harmonics are used. When considering a section of a wave along a latitude circle, this is equivalent to a sinusoidal shape. Because the propagation of the wave is fundamentally caused by an imbalance of the forces acting on the air (which is often thought of in terms of air parcels when considering wave motion), the types of waves and their propagation characteristics vary latitudinally, principally because the Coriolis effect on horizontal