Clouds are classified by appearance and altitude, characteristics named in Latin. Formed by water vapor and ice crystals, clouds usually mean approaching precipitation.

What are Clouds?

Clouds form from the process of condensation, a cycle of gas or vapor changing to liquid. Water can turn into three different forms,

• Solid, or ice

• Gas

• Liquid, or water

Water evaporates into the air turning into gas or vapor, depending on temperature. As the air cools, the water vapor condenses into water droplets or ice crystals. These water droplets and ice crystals form clouds. Clouds are made of tiny ice crystals and water vapor, depending on altitude.

Main Cloud Categories

Clouds are categorized by their appearance and altitude. Luke Howard (1772 - 1864) developed a way of categorizing clouds by describing their characteristics in Latin. There are four main types of clouds, based on appearance:

• Cirro, or stringy, or hair-like
• Cumulus, or heaped or pile
• Stratus, or layered
• Nimbus, or rain bearing

Based on altitude there are three main types:

• High Layered - Cirro
• Middle Layered - Alto
• Low Layered - Stratus

Clouds are classified by their appearance and altitude, named by using a combination of Latin words.

10 Main Types of Clouds

1. Cirrus - High-layered clouds, forming above 20,000 feet, appearing white, like delicate strands or long streaks, called "mares tails". These wispy clouds are made of ice crystals. Cirrus clouds can be a warning for bad weather to come.
2. Cirrostratus - High-layered clouds that often cover the entire sky with an almost transparent sheet. They make halos appear around the sun or moon. Cirrostratus clouds form ahead of storms.
3. Cirrocumulus - Rippling rows of patchy clouds, which appear like fish scales, known as a "mackerel sky". Cirrocumulus clouds form when the wind changes direction, known as wind shear. They can be a sign of precipitation, forming in front of advancing storms.
4. Altostratus - Forming between 6,000 to 20,000 feet, these are middle layered clouds that are made of ice crystals and water droplets. These appear as a thick gray or bluish-white layer of cloud cover, covering the entire sky. These clouds let the sunlight or moonlight through. Altostratus clouds are known to produce widespread snow or rain.
5. Altocumulus - Gray patches forming in bands in the middle atmosphere. These clouds are bigger than cirrocumulus clouds. Altocumulus clouds have sharp edges due the fact that they contain more water droplets than ice crystals.
6. Stratus - These clouds appear low layered, just above the ground, as wispy fog. Stratus clouds cause gray overcast skies with drizzle.
7. Stratocumulus - These clouds appear as low lumpy clouds forming in rows or patches. These clouds may not bring rain but they appear as threatening clouds.
8. Nimbostratus - As their name means in Latin, these rain clouds develop as low layered clouds. They block the sunlight, with low, dark clouds. They appear "ragged", composed of water droplets, which cause precipitation, depending on the air temperature. These clouds form below 6,000 feet in the atmosphere.
9. Cumulus - Clouds can also form vertically called Cumulus clouds. These big, heaped clouds look like puffs of cotton. Cumulus clouds develop from the process of convection, “rapid local ascent when heated air at the earth’s surface rises in the form of thermal currents” (BBC, 2007).
10. Cumulonimbus - Meaning heaped rain cloud, the cumulonimbus can develop with a half hour, into towering “cauliflower-like” heap of clouds.They can grow vertically to almost 40,000 feet, developing into thunderstorms, called giant cumulonimbus clouds.

Sources:

Cox, John D. Weather For Dummies. 2000. Wiley Publishing, Inc. Indianapolis, Indiana.