|Pico Veleta, Sierra Nevada
© Copyright by the observers
The rare phenomenon of a lower light column can be seen below the moon. These columns are created by light reflection at horizontally oriented plate ice crystals in the atmosphere. Perfectly flat oriented crystals in a constant altitude below the observer and the light source would produce a reflected image of the moon. But the crystals show small deviations from the horizontal orientation and are also positioned at different heights. This leads to the elongated form of the reflection and if the light source has a low elevation above the horizon even to a column formed appearance. This effect is very similar with the light column that can be seen below the setting or rising sun on a water surface.
M.G.J. Minnaert: "Light and Color in the Outdoors", Springer-Verlag