© George Anderson
Wokingham, England, United Kingdom of Great Britain and Northern Ireland
Latitude: 51° 25' 4'' N
Longitude: 0° 51' 48'' W
25 June 2014 1938 (Local Time)
Camera direction: towards NNW
Image P/S code: P.1.16
Image I.D.: 5563
CL = 0, CM = 0, CH = 1
This is the second image in a series of three photographs that show the development of Cirrus uncinus homomutatus. It was taken 11 minutes after the first picture.
The original aircraft contrail at 1 and 2, at the bottom of the picture, is fragmenting into tufts of cloud at 3 and 4. From these tufts, filaments of Cirrus homomutatus fill the picture.
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This photograph is the first in a sequence of three images showing the development of Cirrus uncinus homomutatus.
Several aircraft contrails (Cirrus homogenitus) are shown in the picture at 1, 2, 3 and 4. However, the main feature is the larger area of Cirrus stretching diagonally across the image. This is Cirrus homomutatus, which has formed by the spreading out of a contrail in a north-westerly upper wind. The original contrail can be seen below and to the left of the Cirrus, stretching diagonally towards the lower right of the picture. Filaments of Cirrus homomutatus extend away from the original contrail towards the top right of the picture.
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This is the final picture in a sequence of photographs that show the development of a Cirrus uncinus homomutatus cloud. It was taken 31 minutes after Image 1 and 20 minutes after Image 2, as the cloud drifted overhead.
The picture shows filaments of Cirrus at 1 and 2 that end in tufts of cloud at 3 and 4 (species uncinus). The tufts are the remnants of the original contrail. Over time, the original aircraft condensation trail (Cirrus homogenitus) has resulted in the development of Cirrus uncinus homomutatus. The term homomutatus is applied to signify the man-made, or anthropogenic, origin of this cloud.
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Persistent aircraft condensation trails at 1 and 2 (contrails) cover much of the sky in this picture. These contrails are classified as Cirrus homogenitus. The name homogenitus is used where the cloud has developed as a consequence of human activity. Because new or recently formed contrails may display a variety of transient shapes, no species, varieties or supplementary features are used in the classification.
Some of the older contrails can be seen to have spread out over time. These clouds have lost their original linear appearance and have transformed or mutated into cloud, taking on the appearance of a more natural-looking Cirrus. This cloud is Cirrus homomutatus at 3 and 4.
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This Cirrus resulted from a single aircraft contrail. The contrail (Cirrus homogenitus) is in the process of mutating into Cirrus floccus homomutatus, characterized by tufts of cloud accompanied by virga; this process would take approximately half an hour. Eventually this led to the total dissipation of the contrail through falling ice crystals. Winds at the aircraft level were very light.
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In this picture there are several aircraft condensation trails (contrails) across the sky, seen at 1, 2 and 3. These are classified as Cirrus homogenitus. Near the horizon there are Cirrus and Cirrostratus fibratus. A Sun pillar rises vertically above the Sun, formed by the reflection of sunlight on ice crystals in the Cirrostratus. The contrail across the middle of the picture is spreading out to form Cirrus fibratus homomutatus and the cloud at the top of the picture has completely transitioned to Cirrus homomutatus, having lost almost all resemblance to its previous linear shape as a contrail.
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This is the second of two images showing the development of Cirrus spissatus homomutatus cloud. The picture was taken only two minutes after Image 1.
The main feature of this photo is an area of Cirrus homomutatus that has rapidly thickened, over the course of just a couple of minutes, into a dense cloud (species spissatus), seen at 1 and 2. The patch of cloud above the aerial is developing into the species floccus. Other patches of the anthropogenic cloud are mutating into straight filaments, suggestive of the species fibratus, and small cloud elements, suggestive of Cirrocumulus. Meanwhile, a prominent contrail in the earlier picture has drifted towards the top right, and so too has the thin, natural Cirrocumulus at a higher level.
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This is the first of two images showing the development of Cirrus spissatus homomutatus.
In this image there are two fairly new contrails (Cirrus homogenitus) at 1 and 2, but the main features are the areas of Cirrus cloud covering most of the picture. This cloud has formed by the spreading out of older contrails and is Cirrus homomutatus (seen at 3 and 4). In particular, in the lower part of the picture, the cloud has lost its original linear, contrail-like structure, such that without constant observation its anthropogenic origin might not be obvious. Indeed, this differentiates homomutatus from homogenitus.
At the top of the picture, the Cirrus homomutatus spans an angle of about 10° (roughly the width of a clenched fist held at arm’s length). The patch of cloud above the aerial is developing into Cirrus floccus homomutatus. At top right of the picture there is naturally formed, thin Cirrocumulus at a higher level.
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This high cloud formed due to the spreading out of an aircraft contrail. By the time of the photograph, it had expanded to a width covering an angle of about 22° (roughly the area of sky covered by the outstretched fingers of a hand at arm’s length). The individual cloud elements are rounded in appearance (2 and 3) and are generally greater than 1° in width. The cloud can be classified as Cirrus floccus homomutatus.
Some naturally formed Cirrus cloud was spreading in from the north-west and the sky was also completely covered with a very thin, milky veil of Cirrostratus nebulosus. The coding is therefore CH = 7.
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Virtually all of the cloud in this photograph is of anthropogenic origin (man-made), formed through the spreading out of aircraft contrails. Below and to the left of centre, the cloud filaments are largely straight (Cirrus fibratus) with an orientation from the top left towards the bottom right (1 and 2). Because of its anthropogenic origin, this is Cirrus fibratus homomutatus. The brighter streaks in the centre of the cloud filaments are remnants of the original contrails (3 and 4). The large arc of cloud lying diagonally across the image above and to the right of the centre has also originated from the spreading out of a contrail. It has parts composed of small rounded elements of less than 1° in width at 6 and 7, which is suggestive of Cirrocumulus. The patch of cloud on the far left also has these elements. Some natural Cirrus is in the sky as well; this is mostly thin and faint fibratus. In this image, there is a hint of some faint background cloud where the sky has a milky appearance, at the top right and top left of the picture (9 and 10).
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All of the clouds in this photograph have formed from the spreading out of aircraft contrails and because of this anthropogenic origin are homomutatus.
At bottom right of the image, there are two recently formed contrails (Cirrus homogenitus). Above this, on the right of the image, a contrail has spread out and displays small elements with an apparent width of less than 1°; this is Cirrocumulus homomutatus. Left of this, there is Cirrus with fine white filaments that are generally straight; this is Cirrus fibratus homomutatus. In the top centre of the image, there is a large area of Cirrus fibratus homomutatus; however, there are also some small elements on the left side suggestive of Cirrocumulus. This cloud has spread from the contrail on its right side and appears to be at a different level from that of the Cirrus on its right, as evidenced by the contrail shadow; the variety duplicatus applies. At the lower left, there is a thicker and more extensive area of Cirriform homomutatus. The full extent cannot be seen because it is outside of the picture, but the cloud is suggestive of Cirrostratus.
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Apart from a few patches of Cumulus fractus, virtually all of the cloud in this photograph is of anthropogenic origin (man-made). The clouds have formed through the spreading out, over time, of persistent aircraft condensation trails (contrails). Contrails (Cirrus homogenitus) are visible near the top right, top left and centre of the image. The contrail in the centre is in the process of transitioning to homomutatus. Elsewhere the original contrails have mutated into extensive areas of Cirrus (Cirrus homomutatus). At the top of the picture, strands of Cirrus take the form of the species fibratus. On the left, the cloud displays small rounded elements suggestive of Cirrocumulus. In the lower part of the picture the cloud is dense (spissatus).
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(NB. Hour of day not specified therefore estimated)
The sky is crossed in every direction by contrails of different ages. As they expand progressively they form fluffy or fibrous clouds and it is impossible to say with certainty whether there are also clouds of natural origin in the sky. Note the pendant swellings, like inverted toadstools, at 1 - 2, typical of recently formed contrails. From an anticyclone in the south-west a strong ridge of high pressure extended over the area. In the higher layers, advection of warm and rather humid air was in progress from the north-north-east. The associated warm front was at about 250 km west-north- west of Farnborough; it caused only light precipitation when it passed.
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