Genus Cirrostratus

Above: Genus Cirrostratus

Genus Cirrostratus

High-level clouds are divided into three kinds, and these are: cirrus, cirrostratus, and cirrocumulus. These clouds are present at the top of the atmosphere. The genus cirrostratus has the same features of cirrus clouds although they do have their distinctions as well. Its color is similar to that of the cirrus clouds, but the latter can produce precipitation. Both belong to the Family A together with cirrocumulus, when cross-classified by height. They are part of the cirriform cloud category and have a single genus, called the cirri.

High-level clouds, with a height of more than 20,000 feet above sea level, have the prefix cirro, and that is how the name cirrostratus came to be. These clouds cannot prevent objects from casting shadows on the ground because they are not thick enough.

Genus Cirrostratus Definition

Genus cirrostratus clouds are widespread clouds that are white in color and lacking in contrast. Due to this lack of contrast, it may sometimes be difficult to determine their thickness. They often have several horizontal layers clumped together but appear as a single layer from the ground. When they are so thin that they can hardly be distinguished, it often means there is plenty of moisture in the high levels of the atmosphere.

They are often used to determine if precipitation is coming in the next 12 to 24 hours. These clouds themselves do not produce any rain. They can either totally cover or partially cover the sky. Its appearance is generally diffused, and lacks the standard structure like grains, masses, and rolls, among others. They may be sometimes confused with very thin stratus clouds but they are distinct by their fibrous appearance and by being white throughout.

Appearance and Composition

Cirrostratus clouds appear to be white and almost transparent, and that is because these clouds are so high up in the atmosphere where humidity is low. Temperature is high in this level and thus these clouds are composed of ice crystals. Sunlight often passes through these clouds, as they are generally thin. Halos can often be observed with cirrostratus clouds and look quite interesting from the ground. The halo can either be white or colored and forms a ring around the sun or moon. Sometimes, only the halo indicates the presence of cirrostratus clouds. The sparseness and smallness of the crystals make the cirrostratus appear transparent.

How are They Formed?

Genus cirrostratus clouds are often formed by the merging of cirrus clouds. When cool and dry air meets moist and warm air, cirrostratus clouds are formed. They normally develop as a product of fair weather days with light winds. These winds normally increase in strength all throughout the day.

These clouds can also signal a change in weather condition. These clouds are formed at any time during the day and night, contrary to the belief that they are formed only during daylight. It’s just that cloud formations are not as easily observed in the dark as it is at night. Being high-level clouds, they are found at an altitude of 20,000 to 42,000 feet. But in particular, they form at above 23,000 feet. They move in a direction generally from the west. They are much slower compared to lower clouds. They typically precede other clouds in cloud bands, together with cirrus clouds.

Cloud Formations

Cirrostratus clouds can form from cirrus clouds that merge. But they can also be formed from the merging of cirrocumulus elements as well. It can also be formed when ice crystals of the cirrocumulus fall. The thinning of the altocumulus clouds can create cirrostratus clouds or when a cumulonimbus clouds’ anvil spreads out. These clouds are often obscured by lower level clouds and so are not given much notice by ordinary people.

Subspecies of Cirrostratus

In the past, genus cirrostratus clouds had no subspecies and because of the lack of structural detail and their unchanging appearance, all clouds under this genus were considered as one and the same. Today, there are already four subspecies of cirrostratus clouds and these are:

  • Cirrostratus Nebulosus are the most common of cirrostratus clouds. Halos are formed around the sun or the moon.


  • Cirrostratus Fibratus clouds are visibly fibrous and patchy and are surrounded by cirrus cloud at times.


  • Cirrostratus Undulates duplicates and form more than one layer of clouds. They are wavy and rippling.


  • Cirrus Duplicatus are separate sheets or layers that merge, with one on top of the other.

Identifying Cloud Types

There are an amazing number of cloud types and subspecies. It is sometimes hard to distinguish clouds, especially high-level clouds since they are at a great height and distance from the ground. But if you know the description of the clouds’ subspecies, you can easily identify them.

The Internet is a good source of pictures of different cloud types. You will be stunned by the beauty of a cirrostratus nebulosus that forms a halo around the sun. It may seem like an optical phenomenon although in reality, it is the ice crystals in the cloud that make a ring around the sun. Genus cirrostratus clouds are, in reality, thin and wispy clouds. They are so thin that they appear like an aura surrounding the sun or moon, for that matter.

Cirrostratus Clouds and the Weather

Like most clouds, genus cirrostratus clouds can indicate good weather. But they can also be the bearer of bad weather such as thunderstorms, cold fronts, and developing troughs. If you will observe cirrostratus clouds for changes in the weather, never forget that they will persist until the actual change has occurred. If it develops and dissipates during the day, it will continue to do so the next day and so on. Even after the change has occurred, the cirrostratus cloud will still continue to develop.

As mentioned, Cirrostratus clouds produce no precipitation but can indicate an approaching weather front. If the cloud is followed by a mid-level cloud, it often means that rain or snow is coming in the next 24 hours.

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