<|im_start|>user
Can you provide a detailed explanation of the different types of clouds and the meanings behind their formations, including their altitude, appearance, and the types of weather they typically indicate, as well as the different classification systems used to categorize clouds and their characteristics?<|im_end|>
<|im_start|>assistant
Clouds are classified into different types based on their general shape and height in the sky. According to the World Meteorological Organization’s International Cloud Atlas, more than 100 types of clouds exist. However, these many variations can be grouped into one of 10 basic types.

The 10 basic types are divided by their height and are as follows:

Low-level clouds (cumulus, stratus, stratocumulus) that lie below 6,500 feet (1,981 m)
Middle clouds (altocumulus, nimbostratus, altostratus) that form between 6,500 and 20,000 feet (1981–6,096 m)
High-level clouds (cirrus, cirrocumulus, cirrostratus) that form above 20,000 feet (6,096 m)
Cumulonimbus clouds tower across the low, middle, and upper atmosphere.
Each type of cloud has its own characteristics such as appearance and altitude. For example:

Cirrus clouds are high-level clouds that are thin and wispy and composed of ice crystals.
Cumulus clouds are low-level clouds that appear puffy and look like cotton balls or popcorn.
Stratus clouds are low-level clouds that hang low in the sky as a flat, featureless layer of grayish cloud1.
These different types of clouds can indicate different types of weather. For example:

Cumulus clouds develop on clear sunny days when the sun heats the ground directly below and are often called “fair weather” clouds.
Stratus clouds are seen on dreary overcast days and are associated with light mist or drizzle.<|im_end|>
