How are Different Cloud Types Named and Defined?
For anyone who has ever gazed up into the vast blue pool that encompasses the Earth, horizon to horizon, they will have noticed on more than one occasion the different cloud shapes dotting the sky. Some may note them as appearing like fluffy bunnies, others may see dragons, others denote them as simply describing the mood of the sky, while another may discern them to be bumpy or wispy. But what is it that is common amongst these descriptions? Reviewing them, all have to do with a physical appearance of the cloud. Describing the physical appearance of a cloud is actually one of two parts in how the different types are defined from one another. The second part of differentiating one type of cloud from another has to do with altitude in the atmosphere at which that cloud exists, and sometimes the ability of that cloud to precipitate. So what are those fluffy looking clouds called anyways, and what does their name indicate about the cloud?
There are five main categories of cloud name roots that help describe a cloud. These roots are cirro-, alto-, cumulo-, nimbo-, and strato-. All are latin in origin and define the height, appearance, and the precipitation ability of a cloud. The roots are combined to name the specific cloud. Starting with cirro-, this root means “a lock of hair” or “curl-like fringe” and describes clouds that have a wispy, hair-like appearance. The root indicates that it is a high-level cloud, existing at about 6,000m and above in altitude. Situated so high in the atmosphere, they are composed of millions of ice crystals that give them their characteristic hairy, or wispy appearance. Some may even describe them as smudged.
The root alto- means “middle”and describes clouds that exist at middle altitudes in the atmosphere, around 4,000m. As you might imagine, the roots cirro- and alto- cannot be combined to describe a cloud seeing as they both partially indicate the height at which a cloud exists.
In contrast to the previous two roots, strato- does not indicate a cloud’s height whatsoever, and can be found at all levels in the atmosphere. Strato- means layer, such as something that is stratiform, or stratified. As such, stratus clouds are those with a layered look, like sheets covering the sky. Fog is actually a type of stratus cloud! The root can be combined with any one of the other roots to name a cloud. For example, a cirrostratus cloud indicates a cloud that is high level, composed of ice crystals, but in layered form. An altostratus cloud describes a mid-level cloud that appears in sheets or bands.
Moving on, the root nimbo- actually come from the Latin word “nimbus” which means “cloud” in Latin. This specifies a nimbus that precipitates, and can be combined with a few of the different roots, except for alto- and cirro-, seeing as these clouds exist above the freezing point in the atmosphere and cannot precipitate since they are composed of ice. Nimbus clouds are low-level clouds, existing from about 2,000m and below, that often precipitate, be it rain, snow, hail, or sleet.
Finally there is cumulo-, meaning “heap or pile.” Cumulus clouds are interesting in that they occur at all levels of the atmosphere and can be combined with any of the roots listed above. At a low level these clouds are the ones people often make out to be fluffy bunnies or cotton balls thanks to their heaped and bulging appearance. Cirrocumulus appear to be round but raggedy white spots that repeat throughout the sky, while altocumulus are a bit softer and larger in appearance. Stratocumulus tend to occur in waves or lines, and often look as though they are connected, hence where the stratiform appearance comes into play. Finally, the largest and most dramatic of the cumulo- family is the cumulonimbus, a massive cloud that can reach the tallest heights of cloud existence in the atmosphere, up to the troposphere, and sometimes beyond into the stratosphere if they have what is called an “overshooting top.” These clouds are those that produce isolated thunderstorms and are often responsible for large hail storms. Reaching all heights within the atmosphere, these clouds tower, and appear ominous with their dark, bulging bases, and icy tops.
When taking a look into the sky, no longer will you simply see cotton balls and bunnies, but perhaps the many individual types, from a cirrostratus, to a cumulonimbus, to a simple cumulus that so makes those fluffy bunnies! All are distinct in their nature and build, and are constructed from a variety of different atmospheric conditions, but there is no denying that each finds common ground in their unique beauty and ability to spark the imagination.
© Weather Forecaster Alexis Clouser
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