Genus Cirrus Clouds

Above: Genus Cirrus Clouds

Genus Cirrus Clouds

Clouds are beautiful to look at. When you look at the sky on a clear day, you are able to see different forms and shapes of the clouds. It is important to get to know clouds. They are not only useful in weather forecasting but they also play a big part in the Earth's climate.

Genus cirrus clouds are the kinds of clouds you see from the airplane window. These are high altitude clouds that are found about 20,000 feet above sea level. Cirrus clouds were named by Luke Howard in 1803 along with cumulus and stratus clouds. These clouds are classified according to their appearance and altitude.

What are Genus Cirrus Clouds?

This type of cloud is found in the highest level of the atmosphere. Genus Cirrus clouds are formed at altitudes of about 20,000 feet above ground. These clouds are named cirrus because they are curly. Cirrus means curly in Latin. These clouds are transparent, wispy, and thin. They resemble mares’ tails. On average, they have a thickness of 100m to 1,500m. Since they are high up in the sky, they are made up of ice crystals. Cirrus clouds are sometimes the forefront of thunderstorms and hurricanes.

How are They Formed?

These clouds are formed at the edge of a warm front. These conditions have atmospheric pressure from 600 mbar up to 200 mbar, from 4,000 meters above sea level and 12,000 meters above sea level, respectively.

These clouds are formed by convection. They tend to be thin in appearance since they are in such high altitudes with low humidity. Natural cirrus clouds have been known to form after the creation of contrails by aircrafts. They can also come from tropical cyclones. They can also form thunderstorms and develop after a thunderstorm has passed.

Genus Cirrus clouds are said to form on other planets such as Mars, Jupiter, Saturn and Uranus. In Mars, it was observed to have produced precipitation. Meanwhile, the cirrus clouds in Jupiter are made up of ammonia.

Cirrus Clouds Sub-forms

Genera cirrus clouds have several sub-forms namely:

  • Cirrus Castellanus’ size is quite large and is rising out of the cloud’s main body. Its name means tower-like or castle-like in Latin.


  • Cirrus Fibratus is the most common cirrus form. It is feather-like. They seldom cover the sky and the sun can be seen shining through the cloud.


  • Cirrus Intortus has a shape of extreme contortion. Their filaments are curved and irregularly arranged.


  • Cirrus Radiatus stretches across the sky and has large radial bands. Its name is derived from Latin meaning striped or rayed.


  • Cirrus Spissatus is the highest of the genera cirrus clouds. They frequently exhibit optical phenomena.


  • Cirrus Uncinus has hooked forms and it is commonly called mares’ tails. They generally signal that rain is approaching.

Relation to Other Clouds and Its Subtypes

Genus cirrus clouds are one of the three high-level clouds. It belongs to the highest altitudes that form above 6,000 meters in temperate regions. The other two are low-level and mid-level altitudes. The cirrus cloud family is referred to as cirriform clouds. These compose of cirrus, cirrostratus and cirrocumulus clouds.

Cirrostratus clouds cover the whole sky. They are whitish and have no distinguishable features. These clouds often indicate moisture in the upper atmosphere, and may mean rains are coming in the next twelve to twenty-four hours. Cirrocumulus clouds are formed through convection. They are composed of ice crystals but also have water droplets. Because a solitary cirrocumulus cloud is small, it is referred to as a cloudlet. 

Significance in Weather Forecasting

Genus cirrus clouds have played a great role in weather forecasting. In the 19th century, they were used to predict incoming hurricanes. Looking at them in the sky, random and individual cirrus clouds do not hold any particular implication on the weather. But large cirrus clouds can be seen as a signal for weather changes, be it a disturbance in the upper air or approaching frontal systems.

The cirrus cloud castellanus is often visible at this point. Cirrus fibratus or cirrus radiates indicate the coming of a weather front. Cirrus clouds turn into cirrostratus clouds when a warm front is approaching. After, the cirrostratus clouds lower and thicken, becoming altostratus and altocumulus clouds. In the case of a cold front, the cirrus clouds get blown away and are replaced by cumulonimbus clouds. Thus, cirrus clouds play a big role for meteorologists to forecast weather.

Effect on Climate

Cirrus clouds have an effect on the Earth’s climate. These clouds cover 25% of the Earth and are responsible for balancing radiation that goes in and out of our planet. Clouds play a role in the greenhouse effect. Observe a cloudless summer sky, and you will realize that the temperature is much higher than if there were clouds present.

Clouds present three major effects on the Earth’s climate. First, clouds are able to reflect sunlight. Cirrus clouds can reflect about 10% of the sun’s visible light. Second, they are part of the greenhouse effect by absorbing thermal radiation and re-radiating it back down to Earth. Lastly, thermal radiation is reflected back to the Earth’s surface.  But it is important to remember that their effect depends upon the type of cloud and the time of day.

Optical Phenomena

The Genus cirrus clouds are able to create optical phenomena. For example, glories, which are similar to a Saint’s halo, can they appear over the head of the observer. These things are created by uniformly-sized droplets in the cloud that backscatters light towards the source. They are formed when ice crystals are aspherical, and the ice crystals are 0.009mm to 0.015mm in length.

Sundogs and halos are also produced by cirrus clouds. Sundogs are found on either side of the sun in the sky, creating bright spots. Halos, on the other hand, are ice crystals that create white and colored spots and arcs in the sky. The cirrus spissatus clouds usually exhibit this kind of optical phenomena.

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