Atmospheric optical phenomena in which the Sun appears to have risen
This article is about the phenomenon of later dawn. Not to be confused with the earlier
False dawn.
A false sunrise is any of several
atmosphericoptical phenomena in which the
Sun appears to have
risen, but is actually still some distance below the horizon. A number of different atmospheric conditions can be responsible for this effect, all of which divert the
sunlight in such a way as to allow it to reach the observer's eye, thereby giving the impression that the light comes directly from the Sun itself. The spread of light can sometimes be deceivingly similar to a true sun.
Several atmospheric phenomena that may alternatively be called a "false sunrise" are:
Simple reflection of the sunlight off the bottom of the clouds.
A type of
ice crystal halo, such as an
upper tangent arc or, more commonly, an upper
sun pillar (similar to a
subsun, but extending above the sun instead of below it). Like all
halos, these phenomena are caused by the reflection and/or refraction of sunlight by
ice crystals suspended in the atmosphere, often in the form of
cirrus or
cirrostratus clouds. The temperature on the ground is irrelevant to their occurrence, meaning that halos can be seen throughout the year and in all climates.
A type of
mirage, specifically the
Novaya Zemlya effect. Restricted mainly to the polar regions, this phenomenon was named after its first observation on
Novaya Zemlya during the third polar expedition led by
Willem Barentsz in 1596/97, when the Sun was seen above the horizon "in his full roundnesse"[1] two weeks before its predicted return after the
polar night. The account, written by officer
Gerrit de Veer, was met with general scepticism for centuries, and not until modern times was the effect proven to be genuine.[2]
The term "false sunrise" should not be confused with "false dawn", which is a term sometimes used to refer to the
zodiacal light.
^Siebren van der Werf, Het Nova Zembla verschijnsel. Geschiedenis van een luchtspiegeling ("The Novaya Zemlya phenomenon. History of a mirage"), 2011;
ISBN978 90 6554 0850.