CLOUD GLOSSARY

GLOSSARY OF TERMS

Genera Terms

Alto means middle.

Cirro, from which cirrus is obtained means "wisp of hair."

Cumulo, from which cumulus is obtained means "heap." Clouds with this designator appear to be piled up. These type clouds form in unstable layers of air. The initial lifting may be due to convective lifting or forced (mechanical) lifting, such as; orographic, frontal or convergence lifting. If the layer is unstable, the air parcel will continue to rise producing a cumulo-form cloud.

Nimbo: This designation means "rain." Thus, nimbostratus and cumulonimbus are clouds from which precipitation occurs.

Strato, from which stratus is obtained means "layer" or "layered." Clouds with this designator form in stable layers of air; except the stratocumulus type which forms in a thin, unstable layer of air.

Species Terms

Calvus: Cumulonimbus in which at least some protuberances of the upper part are beginning to lose their cumuliform outlines but in which no cirriform parts can be distinguished. Protuberances and sproutings tend to form a whitish mass, with more or less vertical striations.

Capillatus: Cumulonimbus characterized by the presence, mostly in its upper portion, of distinct cirriform parts of clearly fibrous or striated structure, frequently having the form of an anvil, a plume or a vast, more or less disorderly mass of hair. Cumulonimbus capillatus is usually accompanied by a shower or by a thunderstorm, often with squalls and sometimes with hail; it frequently produces very well-defined virga.

Castellanus: Clouds which present, in at least some portion of their upper part, cumuliform protuberances in the form of turrets which generally give the clouds a crenelated appearance. The turrets, some of which are taller than they are wide, are connected by a common base and seem to be arranged in lines.

Congestus: Cumulus clouds which are markedly sprouting and are often of great vertical extent. Their bulging upper part requently resembles a cauliflower.

Fibratus: Detached clouds or a thin cloud veil, consisting of nearly sraight or more or less irregularly curved filaments which do not terminate in hooks or tufts.

Floccus: A species in which each cloud unit is a small tuft with a cumuliform appearance, the lower part of which is more or less ragged and often accompanied by virga.

Fractus: clouds in the form of irregular shreds, which have a clearly ragged appearance.

Humilis: Cumulus clouds of only a slight vertical extent. They generally appear flattened.

Lenticularis: Clouds having the shape of lenses or almonds, often very elongated and usually with well-defined outlines; they occasionally show irisation. Such clouds appear most often in cloud formations of orographic origin, but may also occur in regions without marked orography.

Mediocris: Cumulus clouds of moderate vertical extent, the tops of which show fairly small protuberances.

Nebulosus: A cloud like a nebulous veil or layer, showing no distinct details.

Spissatus: Cirrus of sufficient optical thickness to appear greyish when viewed towards the sun.

Stratiformis: Clouds spread out in an extensive horizontal sheet or layer.

Uncinus: Cirrus often shaped like a comma, terminating at the top in a hook, or in a tuft the upper part of which is not in the form of a rounded protuberance.

Varieties

Duplicatus: Superposed cloud patches, sheets or layers, at slightly different levels, sometimes partly merged.

Intortus: Cirrus, the filaments of which are very irregularly curved and often seemingly entangled in a capricious manner.

Lacunosus: Cloud patches, sheets or layers, usually rather thin, marked by more or less regularly distributed round holes, many of them with fringed edges. Cloud elements and clear spaces are often arranged in a manner suggesting a net or a honeycomb.

Opacus: An extensive cloud patch, sheet or layer, the greater part of which is sufficiently opaque to mask completely the sun or moon.

Perlucidus: An extensive cloud patch, sheet or layer, with distince but sometimes very small spaces between the elements. The spaces allow the sun, the moon, the blue of the sky or over-lying clouds to be seen.

Radiatus: Clouds showing broad parallel bands or arranged in parrallel bands, which, owing to the effect of perspective, seem to converge towards a point on the horizon or, when the bands cross the whole sky, towards two opposite points on the horizon, called "radiation point(s)."

Translucidus: Clouds in an extensive patch, sheet or layer, the greater part of which is sufficiently translucent to reveal the position of the sun or moon.

Undulatus: Clouds in patches, sheets or layers, showing undulations. These undulations may be observed in fairly uniform cloud layers or in clouds composed of elements, separate or merged. Sometimes a double system of undulations is evident.

Vertebratus: Clouds, the elements of which are arranged in a manner suggestive of vertebrae, ribs, or a fish skeleton. The term applies mainly to cirrus.