You should try to learn these 10 cloud
names. Not just because
be on a quiz but because you will be able to spot them and name them
when you see these different kinds of clouds outdoors.
There is a smart and a not-so-smart way of
these names. The not-so-smart way is to just memorize them.
will inevitably get them mixed up. A better way is to recognize
the cloud names are made up of key words. The 5 key words
mostly tell you something about the cloud altitude and appearance.
Drawing a figure like this on a blank sheet of
paper is a good way to
cloud identification and classification.
Each of the clouds above has a box reserved for
it in the figure. You should be able eventually to fill each box
with a name, a sketch, and a short description of each cloud type.
Clouds are classified according to the altitude at which they form and the appearance of the cloud. There are two key words for altitude and two key words for appearance.
Clouds are grouped into one of three altitude
categories: high, middle
Cirrus or cirro
identifies a high altitude
cloud. There are three types of clouds found in the high altitude
Alto in a cloud name means the cloud is found at middle altitude. The arrow connecting altostratus and nimbostratus indicates that they are very similar. When an altostratus cloud begins to produce rain or snow its name is changed to nimbostratus. A nimbostratus cloud is also often somewhat thicker and lower than an altostratus cloud. Sometimes it might sneak into the low altitude category.
It is very hard to just look up at the sky and directly determine a cloud's altitude. You will need to look for other clues to distinquish between high and middle altitude clouds. We'll learn about some of the clues when we look at cloud pictures and discuss individual cloud types later in this lecture.
There is no key word for low altitude clouds. Low altitude clouds have bases that form 2 km or less above the ground. The summit of
Clouds can have a patchy of puffy (or lumpy,
wavy, or ripply) appearance.
are cumuliform clouds and will have cumulo or cumulus
In an unstable atmosphere cumuliform clouds will
Strong thunderstorms, cumulonimbus clouds, can produce severe and
dangerous weather conditions.
Stratiform clouds grow horizontally and form layers. They form when the atmosphere is stable. You'll find strato or stratus in the cloud name.
are sometimes considered to be a third type of cloud appearance.
The last key word, nimbo
or nimbus, means
precipitation. Only two of the 10 cloud types are able to produce
amounts of) precipitation. It's not as easy as you might think to
Nimbostratus (Ns) clouds tend to produce fairly light precipitation over a large area. Cumulonimbus (Cb) clouds produce heavy showers over smaller and more localized areas. Thunderstorm clouds can also produce hail, lightning, and tornadoes. Hail would never fall from a Ns cloud.
While you are still learning the cloud names you might put the correct key words together in the wrong order (stratonimbus instead of nimbostratus or nimbocumulus instead of cumulonimbus).
the cloud chart from earlier. We've added the three altitude
along the vertical side of the figure and the two appearance categories
the top. By the end of the class we will add a picture to each of
because the air at high altitudes is very cold and cold air can't
moisture (the saturation mixing ratio for cold air is very
clouds are also often blown around by fast high altitude winds.
Filamentary means "stringy" or "streaky". If you
imagine trying to paint a Ci cloud you
would dip a
small pointed brush in white paint brush it quickly and lightly across
colored canvas. Here are
some pretty good photographs of cirrus
clouds (they are all from a Wikipedia article on
A cirrostratus cloud is a thin uniform white layer cloud (not purple as shown in the figure) covering part or all of the sky. They're so thin you can sometimes see blue sky through the cloud layer. Haloes are a pretty sure indication that a cirrostratus cloud is overhead. If you were painting Cs clouds you could dip a broad brush in white paint (diluted perhaps with water) and then paint back and forth across the canvas. Note the two views show you looking through the cloud at the sun (left) and from the side (right) to emphasize how thin these high altitude layer clouds are.
Cirrus and cirrostratus clouds are fairly common. Cirrocumulus clouds are a little more unusual.
paint a Cc cloud you would dip a sponge in white paint and press it
against the canvas. You would leave a patchy, splotchy appearing
(sometimes you might see small ripples). It is the patchy (or
appearance that makes it a cumuliform cloud.
This is a flatter crystal and is called a plate. These crystals tend to all be horizontally oriented and produce sundogs. A sketch of a sundog is shown below.
enough that you probably won't see a shadow if you look down at your
feet. The sun may or may not be visible through the cloud. When (if) an altostratus cloud begins to produce
name is changed to nimbostratus. The figure shows you looking
through the cloud at left and viewing the cloud from the side at right.
are shown below (the first is from a
Wikipedia article, the middle and right
photograph are from an Environment
Canada web page)
This cloud name
unusual because the two key words for cloud appearance have been
combined, but that's a good description of this cloud type - a "lumpy
Because they are closer to the ground, the separate patches of Sc are about fist size. The patches of Ac, remember, were about thumb nail size (sources of the photographs: left photo, right photo ). If the cloud fragments in the photo at right are clearly separate from each other (and you would need to be underneath the clouds so that you could look up) these clouds would probably be "fair weather" cumulus. If the patches of cloud are touching then stratocumlus would be the correct designation.
(here viewed from the side) are usually thick enough to completely hide
There are lots of
features on cumulonimbus clouds including the flat anvil top and the
lumpy mammatus clouds sometimes found on
the underside of the
downdraft winds hit the ground below a
spread out horizontally underneath the cloud. The leading edge of
winds produces a gust front (dust front might be a little more
Winds at the ground below a thunderstorm can exceed 100 MPH, stronger
The top of a
thunderstorm (violet in the sketch) is cold enough that it will
composed of just ice crystals. The bottom (green) is composed of
droplets. In the middle of the cloud (blue) both water droplets
exist together at temperatures below freezing (the water droplets have
time freezing). Water and ice can also be found together in
clouds. We will see that this mixed phase region of the cloud is
for precipitation formation. It is also where the electricity
produces lightning is generated.
The top left photo shows a thunderstorm viewed from space (source: NASA Earth Observatory). The flat anvil top is the dominant feature. The remaining three photographs are from the UCAR Digital Image Library. The bottom left photograph shows heavy by localized rain falling from a thunderstorm. At bottom right is a photograph of mammatus clouds found on the underside of the flat anvil cloud.
Here's one final feature to look for at the bottom of a thunderstorm.