Image credit: C Messier - Own work, CC BY-SA 3.0, Circumhorizontal arcĬircumhorizontal arcs are visually similar in some ways to cloud iridescence, but are in fact part of the halo family. The color patterns tend to be unordered or chaotic, with a pastel look to them. Such colors can occur in high-level cirrus clouds or in mid-level altocumulus clouds or in some polar stratospheric clouds known as nacreous clouds or mother-of-pearl clouds. Their apparent convergence toward the sun is a perspective effect.Ĭolors in clouds similar to those seen in oil films in puddles, due to diffraction of light by small water droplets or ice crystals. Rays of light that appear to radiate from the location of the Sun in the sky, caused by sunlight streaming through cloud gaps and emphasized by the cloud-shadowed regions where no sunlight is streaming. It is seen only when the clouds are observed from above, and is caused by reflection of sunlight from the flat ice crystals of which the clouds are composed. Wilson saw a glory while working as an observer at the Ben Nevis weather station in Scotland, and that sight inspired him to study clouds and eventually led to the development of his cloud chamber.Ī special type of halo that appears as an enlongated mirror image of the Sun in the clouds. To see a glory, the observer must be between the Sun and the cloud, so it often seen from aircraft. Each ring is red on the outside and bluish toward the centre. One or more diffuse concentric rings of colored light around a shadow image of an object projected on a cloud of refracting water droplets. The aureole of a lunar corona can be enhanced if seen through a cloud layer that is not too thick and/or has breaks.Ī type of halo consisting of a pair of bright spots to the left and right of the Sun.Ī vertical shaft of light extending upward or downward from the Sun, generally seen when the Sun is very low in the sky, and caused by reflection of sunlight from ice crystals that form high, thin cirrostratus clouds. It may be the only visible part of the corona, particularly for those associated with the Moon. It appears as a whitish or bluish-white disk that fades to a pale reddish-brown toward the circumference of the disk. The central bright area of a corona is called the aureole. Bishop's ring coronas can be larger than the usual coronas associated with thin clouds, which are smaller than halos. It is caused by scattering of light from very small (~ 1 micrometer, or 1/1000 of a mm) particles, usually stratospheric dust or ash or sulphate droplets from volcanic eruptions that are suspended in the atmosphere. Coronas usually occur in the presence of thin clouds, but a particular type, known as the Bishop's ring corona, occurs in the absence of clouds. In a corona the reddish tones are at the outer part of the rings. One or more diffuse concentric rings of light around the Sun or Moon, formed by diffraction of light as it moves through water droplets in the atmosphere the rings may have more color than halos. Halos are large - in the most common halo, the angle between the centre and the ring is 22 degrees (approximately the angle defined by the span of a hand at arm's length, as in this example), but other even larger halos are also possible.Ĭorona (diffraction ring around the Sun or Moon, not the corona composed of plasma surrounding the Sun) If colors are present the reddish tones are at the inner part of the rings. The term for various circles or arcs of light around the sun or Moon, caused by reflection and refraction of light as it moves through ice crystals in the atmosphere. The following phenomena fall under part 1 of the above definition, and philatelic items referring to them are included in this page. The interaction of charged particles from the sun (the solar wind) with certain atmospheric gases.Ītmospheric Optical Phenomena included in this page:.The interaction of light from the Sun or the Moon with certain components of the atmosphere (cloud water droplets or ice crystals, liquid or solid precipitation, dust, water vapour and the gases of the atmosphere itself) or with certain atmospheric structures (such as the vertical distribution of temperature and/or humidity) or.We define atmospheric optical phenomena to be the visual results of: If readers know of additional information or images, please contact the authors using the e-mail addresses at the bottom of this page.Ītmospheric Optical Phenomena: Definition Catalog numbers, years of issue, and notes on the items featured are given when available. (except Rainbows and Auroras) halo Sun pillarīelow is a checklist of Atmospheric optical phenomena (except Rainbows and Auroras) on postal items (stamps, souvenir sheets, aerogrammes, postal cards, etc.). Atmospheric Optical Phenomena (except Rainbows and Auroras) Atmospheric Optical Phenomena
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