Altocumulus clouds are a type of mid-level cloud that form between 6,000 to 20,000 feet above ground level. They are characterized by globular masses or rolls in layers or patches, with individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. Altocumulus clouds are usually composed of droplets, but may also contain ice crystals, giving them a slightly more ethereal appearance than the big and fluffy lower level cumulus. They are thin, mid-altitude clouds that are often arranged in waves or lines which may be joined to form a continuous layer.
Altocumulus clouds can form in several ways, such as through convection or as a result of a weakening warm front. They are usually found in settled weather and are one of the most diverse cloud types, with many different species. Some of the most common species include:
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Altocumulus stratiformis: This is the most common type of altocumulus, looking like flat-bottomed puffy clouds packed tightly together but separated by small rivers of sky. These can sometimes extend over the whole sky but are more common in smaller patches.
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Altocumulus lenticularis: This is one of the most spectacular cloud types, also known as lenticular clouds, which are lens-shaped clouds that form over hilly areas.
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Altocumulus castellanus: This type of cloud frequently signals the development of thunderstorms later in the day, as it shows instability and convection in the middle levels of the troposphere.
Altocumulus clouds are generally not associated with precipitation, but if rain does fall, it doesnt reach the ground. This precipitation can be seen in the form of virga, where the rain is re-evaporated before reaching the surface.
In summary, altocumulus clouds are a type of mid-level cloud that are characterized by globular masses or rolls in layers or patches. They are usually composed of droplets, but may also contain ice crystals, and are not associated with precipitation. Altocumulus clouds can take on many different shapes and sizes, and are often arranged in waves or lines which may be joined to form a continuous layer.
