Cloud Types

Clouds are divided into 4 main groups. Each group depends on the height of the cloud's base above the earth's surface. The following table provides information about each group and the cloud classes associated with them.

High Clouds

The high cloud group consists of Cirrus, Cirrostratus, and Cirrocumulus clouds. High clouds are made of ice crystals due to the cold air in the upper sky. The base of a high cloud above the surface can be anywhere from 6000-18000m in the tropics to 3000-8000m in the polar regions.

Cirrus
Cirrus clouds are the most common of the High Cloud (5000-13000m) group. They are composed entirely of ice and consist of long, thin, wispy streamers. They are commonly known as "mare's tails" because of their appearance.  Cirrus clouds are usually white and predict fair weather.

Cirrostratus
Cirrostratus clouds belong to the High Cloud (5000-13000m) group. They are sheetlike thin clouds that usually cover the entire sky.  The sun or moon can shine through Cirrostratus clouds as shown in the photo at left (Yes, the moon is in this photo...can you find it?). Sometimes, the sun or moon will appear to have a halo around it when in the presence of Cirrostratus. The ice crystals from the cloud refracts the light from the sun or moon, creating a halo. Cirrostratus clouds usually come 12-24 hours before a rain or snow storm. This is especially true if Middle group clouds are associated with it.

Cirrocumulus
Cirrocumulus clouds belong to the High Cloud group (5000-13000m). They are small rounded puffs that usually appear in long rows. Cirrocumulus are usually white, but sometimes appear grey as in the photo.  If these clouds cover a lot of the sky, it is called a "mackerel sky" because the sky looks like the scales of a fish. Cirrocumulus are usually seen in the winter time and indicate fair, but cold weather.

Middle Clouds

The middle cloud group consists of Altostratus and Altocumulus clouds. Middle clouds are made of ice crystals and water droplets. The base of a middle cloud above the surface can be anywhere from 2000-8000m in the tropics to 2000-4000m in the polar regions.

Altostratus
Altostratus belong to the Middle Cloud group (2000-7000m up). An altostratus cloud usually covers the whole sky and has a grey or blue-grey appearance. The sun or moon may shine through an Altostratus cloud, but will appear watery as seen in the photo at left.  An altostratus cloud usually forms ahead of storms with continuous rain or snow. Occasionally, rain will fall from an altostratus cloud.

Altocumulus
Altocumulus clouds are part of the Middle Cloud group (2000-7000m up). They are greyish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups and are about 1 km thick.  If you see Altocumulus clouds on a warm humid morning, then expect thunderstorms by late afternoon.

Low Clouds

Stratus
Stratus belong to the Low Cloud (surface-2000m up) group. They are uniform grey in colour and almost cover the entire sky. Stratus usually looks like a fog that doesn't reach the ground. Light mist or drizzle is sometimes associated with Stratus clouds.

Stratocumulus
Stratocumulus clouds belong to the Low Cloud (surface-2000m) group. These clouds are low, lumpy, and gray. Most form in rows with blue sky visible in between.  Precipitation rarely occurs with Stratocumulus clouds. To distinguish between a Stratocumulus and an Altocumulus cloud, point your hand toward the cloud. If the cloud is about the size of your fist, then it is Stratocumulus.

Nimbostratus
Nimbostratus belong to the Low Cloud (surface to 2000m up) group. They are dark grey with a ragged base. Nimbostratus clouds are associated with continuous light rain or snow.
 

Clouds with vertical growth

Clouds with vertical growth include Cumulus and Cumulonimbus clouds. Vertical growth clouds span all levels of the troposphere and can even shoot into the stratosphere. The clouds develop by warm air rising from the surface. Cumulus and Cumulonimbus clouds provide the most interesting and severe weather to our planet. 

Cumulus
Cumulus clouds belong to the Clouds with Vertical Growth group. They are puffy white or light gray clouds that look like floating cotton balls. Cumulus clouds have sharp outlines and a flat base. Cumulus clouds generally have a base height of 1000m and a width of 1km.  Cumulus clouds can be associated with good or bad weather. Cumulus humilis clouds are associated with fair weather. Cumulus congestus clouds are usually associated with bad weather. Their tops look like cauliflower heads and light to

Cumulonimbus
Cumulonimbus clouds belong to the Clouds with Vertical Growth group. They are generally known as thunderstorm clouds. A cumulonimbus can grow up to 10km high. At this height, high winds will flatten the top of the cloud out into an anvil-like shape. Cumulonimbus clouds are associated with heavy rain, snow, hail, lightning, and tornadoes.

Answer the following:

1  Name the four groups of cloud type.

2  Name two types of 'low cloud'

3  What kind of weather would you expect with Cirrus cloud?

4  What kind of cloud would you associate with heavy rain and tornedos?