Altostratus Pannus

Above: Altostratus Pannus

Altostratus Pannus

Altostratus pannus clouds are a type of cloud which is characterized by being very expansive. Typically, altostratus pannus clouds will have a large horizontal extent, which means that they can cover a large area of the sky. They also normally have great vertical heights, i.e. the distance between the pinnacle of the clouds and the bases. The contents of such clouds are also usually mixed. While other clouds are normally formed with water and ice crystals, altostratus pannus clouds are usually made of a mixture of different products such as water, ice and in some cases snow as well.

What height are altostratus pannus clouds found?

Altostratus pannus clouds belong to the genus altostratus, and they therefore conform to the general morphology of this genus as far as height is concerned. The altostratus pannus clouds therefore form at a distance of about six thousand to sixteen thousand feet above sea level.

Classification of altostratus pannus clouds

Altostratus pannus clouds are middle level clouds.

How are altostratus pannus clouds formed?

Altostratus pannus clouds are formed in more or less the same way as the other types of clouds, with only a few alterations that make them stand out from the rest. Basically, altostratus pannus clouds will form when air bearing a large amount of water is forced upward, where the temperatures are lower. At these altitudes, the water in the air condenses, forming clouds. The agent causing the upward rise of the air containing water could either be another cold air front, convectional currents or movement up a mountain.

What do altostratus pannus clouds look like?

The defining feature of altostratus pannus clouds is their expansiveness. These clouds are normally massive; they extend for large distances both horizontally and vertically. They are normally composed of water or ice. The composition of the clouds is normally stratified. This means that:

  • The upper part of the clouds are formed by ice crystals


  • The middle part of the clouds is made of a mixture of ice and cool water. Snow may also be a feature of this part of the cloud.


  • The bases of the clouds have a predominance of super cooled water.


There are many instances where the clouds are formed have only two layers; the upper part comprising ice crystals and the lower part with supercool water.

How common are altostratus pannus clouds?

Altostratus pannus clouds are more common in regions such as the temperate regions, where the air contains just the right amount of water so as to condense at the middle levels of 6,000 to 16,000 feet. In other areas such as climates with very low humidity, the condensation normally occurs very high up, and in such situations the clouds that form aren’t characteristic altostratus pannus clouds. By the same token, areas that have high humidity such as the tropical regions normally have clouds that form at very low altitudes, and these are normally much thicker due to greater water content.

Where can I see altostratus pannus clouds?

Altostratus pannus clouds are normally formed in regions where the moisture content in the air is not too much or too little. They can therefore be seen in areas of moderate humidity.

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