© Frank Le Blancq
Noirmont Common, St. Brelade, Jersey
Latitude: 49° 10' 18'' N
Longitude: 2° 10' 8'' W
18 September 2010 1739 (Local Time)
Camera direction: towards SW
Image P/S code: S.13.1.5.1
Image I.D.: 4994
CL = 0, CM = 0, CH = 6
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Cirrostratus fibratus, circumzenithal arc and supralateral arc
The transparent white cloud is a thin veil of Cirrostratus, which only partly covered the sky. The presence of striations in the cloud suggest the species fibratus. Cirrostratus is composed of ice crystals which often produce halo phenomena, as in this case. The main feature is a strong circumzenithal arc with red colouration on the outside. Below and to the left of this arc is a much fainter supralateral arc extending towards the lower left of the photograph.
A circumzenithal arc will occur only when the light source (for example, the Sun) is at an elevation of less than 32° above the horizon. The circumzenithal arc appears high in the sky and is centred on the zenith, the point of the sky directly above the observer.
A supralateral arc is a rarer and fainter arc of spectral colour that also forms only when the light source is below 32° elevation. The supralateral arc may be mistaken for the 46° halo, but can be distinguished from it by the somewhat brighter and more coloured appearance of the supralateral arc. The apex of the arc is near to or touching the circumzenithal arc.
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© Frank Le BlancqNoirmont Common, St. Brelade, JerseyLatitude: 49° 10' 18'' NLongitude: 2° 10' 8'' W18 September 2010 1739 (Local Time)Camera direction: towards SWCL = 0, CM = 0, CH = 6Image P/S code: S.13.1.5.1Image I.D.: 4994
Low pressure covered much of the North Atlantic and Scandinavia. High pressure was established west of the Azores, Portugal, extending a ridge over north-west France and into Germany. A weak warm front was moving east over the Irish Sea, with the following cold front approaching western Ireland.
© Deutscher Wetterdienst
The Brest, France (WMO 07110) sounding from 1200 UTC shows that the wind at Cirrostratus level was north-west at about 25 kt (12.9 m/s), with a dry atmosphere evident from the surface to upper levels. An exception can be seen at 380 hPa (approximately 7 800 m), where a sharp increase in humidity is evident at the estimated height of the Cirrostratus cloud.
© University of Wyoming
The IR satellite image at 1800 UTC (1 hour and 20 minutes after the photograph) shows a basic frontal pattern in the upper (cold-topped) cloud over western UK and the East Atlantic. Disorganized upper cloud is seen in the north-west flow over the western and central English Channel, where the image was taken.
© EUMETSAT, 2010
Circumzenithal arc
This brightly coloured circumzenithal arc was formed by the refraction of sunlight through the ice crystals of a Cirrus fibratus cloud. The circumzenithal arc is a halo phenomenon that occurs only when the light source (for example, the Sun) is at an elevation of less than 32° above the horizon.
The arc is centred on the zenith - the point of the sky directly above the observer - and so is observed high in the sky. It typically displays bright spectral colours, as shown in this picture. A distinguishing feature is that red is always on the lower, outside of the arc, and violet is always on the upper, inside.
The exact location, length and brightness of the circumzenithal arc all vary with the Sun's elevation. When the elevation is about 22°, the arc touches the large (46°) halo, if it is visible. However, more frequently than not, the large halo is not seen – as in this case.
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© George AndersonFarnborough, Hampshire, United Kingdom of Great Britain and Northern IrelandLatitude: 51° 16' 39'' NLongitude: 0° 46' 5'' W22 July 2010 1810 (Local Time)Camera direction: towards WImage P/S code: P.13.1.5.1Image I.D.: 4068
A complex halo display
This magnificent halo display was formed by the refraction and reflection of sunlight through diamond dust at an altitude of 1 100 m in Neklid, Klinovec, Ore Mountains, Czech Republic.
Such complex displays are usually observed only in polar regions, although they may occasionally occur in mountains when there are ice crystals in the air, as in this case. The dust-like specks in this photograph are in fact the diamond dust ice crystals sparkling in the sunlight.
The halos visible in this picture are: a 22° halo; a parhelic circle and parhelia; a lower tangent arc; infralateral arcs; an upper tangent arc with a suncave Parry arc; a heliac arc; a supralateral arc that touches a circumzenithal arc; and four Tape arcs (also known as 46° Parry arcs).
Some of these halo types are quite common, such as the 22° halo and the parhelia. Others, however, are less frequently seen, and some, such as the heliac arc and Tape arcs, are rarely witnessed.
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© Claudia HinzNeklid, Klinovec, Czech RepublicLatitude: 50° 24' 12'' NLongitude: 12° 56' 19'' E30 January 2014 1056 (Local Time)Camera direction: towards SSEImage P/S code: P.13.1Image I.D.: 4204
Cirrostratus fibratus undulatus with 22° halo
The double layer of Cirrostratus is identified by the alignment of fibratus striations. In the lower layer, the fibratus is aligned north-east to south-west; the higher layer is at a right angle to the lower layer; that is, south-east to north-west.
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© Stephen BurtStratfield Mortimer, near Reading, Berkshire RG7, United Kingdom of Great Britain and Northern IrelandLatitude: 51° 22' 12'' NLongitude: 1° 2' 24'' W02 December 2009 1011 (Local Time)Camera direction: towards SECL = 0, CM = 0, CH = 8Image P/S code: P.3.2Image I.D.: 5491