False sunrise

This article is about the phenomenon of later dawn. Not to be confused with the earlierFalse dawn.

A "false sunrise" (in the form of a fragmentary upperSun pillar) as seen nearBologna,Italyin October 2008. Note the "lake-reflection" effect which is not real because there is no water in between.

Afalse sunriseis any of severalatmosphericoptical phenomenain which theSunappears to haverisen,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 thesunlightin 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 resemble that of the 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 ofice crystal halo,such as anupper tangent arcor, more commonly, an uppersun pillar(similar to asubsun,but extending above the sun instead of below it). Like allhalos,these phenomena are caused by the reflection and/or refraction of sunlight byice crystalssuspended in the atmosphere, often in the form ofcirrusorcirrostratus 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 ofmirage,specifically theNovaya Zemlya effect.Restricted mainly to the polar regions, this phenomenon was named after its first observation onNovaya Zemlyaduring the third polar expedition led byWillem Barentszin 1596/97, when the Sun was seen above the horizon "in his full roundness"two weeks before its predicted return after thepolar night.The account, written by officerGerrit de Veer,was met with general skepticism for centuries, and not until modern times was the effect proven to be genuine.

The term "false sunrise" should not be confused with "false dawn", which is a term sometimes used to refer to thezodiacal light.

See also

• False sunset
• Halo (optical phenomenon)
• Mirage
• Novaya Zemlya effect
• Subsun
• Sun pillar
• Upper tangent arc
• Zodiacal light