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Weather school: It’s all about the clouds

TYPING Our current naming system classifies clouds by their height, then by their looks

Clouds, where would we be without clouds? Besides being esthetically pleasing to look at (if you’re not looking at them all the time), without them there would be no rain or snow, thunder or lightning, or rainbows! I know we have discussed the topic of clouds in the past, but I can’t seem to find when we last revisited this topic. So, to finish off the last few weeks of summer, let’s take a detailed look at clouds: the different types, how they are named and how they are formed. In the words of July Garland: “Behind every cloud is another cloud.”

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If we were to define a cloud, we could say it is a visible collection or aggregate of tiny water droplets or ice crystals floating or suspended in the air. Stealing a line from Meteorology Today, “some clouds are found only at high elevations, while others nearly touch the ground. Clouds can be thick or thin, big or little — they exist in a seemingly endless variety.” Identifying all the different types of clouds can be a little tough, but with some practice, you can become reasonably proficient at identifying them.

Our current method of naming and classifying clouds was developed in 1803 by Luke Howard, an English naturalist. His system employed Latin words to describe the clouds as they appear from the ground. Clouds that appeared to look like sheets were called stratus, which is Latin for “layer.” Puffy clouds were called cumulus, which is Latin for “heap.” Wispy clouds were called cirrus, which is Latin for “curl of hair,” and finally, rain clouds were called nimbus, meaning “violent rain.” In essence, Howard’s system had four different cloud types. These types could then be combined to cover other types of clouds. For example, stratus clouds that have rain falling from them would be called nimbostratus, cirrus clouds that form a layer would be called cirrostratus, and so on.

In 1887, Abercromby and Hildebrandsson expanded Howard’s system by creating four different groups into which clouds can be divided into based on height. These would be high clouds, middle clouds, low clouds, and a fourth group for clouds that span more than one region, or what we call “vertically developed” clouds.

This is the system we use today. Clouds are classified by the height at which they occur and then by their appearance. The list below shows the four major cloud groups and their types.

This addition to the naming and classifying of clouds does at first seem fairly simple and straightforward, but a couple of things make it a little confusing. First of all, we have cloud types of stratus (layer) and cirrus (wispy). To add in the height of the cloud we could use the term “cirrus” for all high clouds, “alto” for middle-level clouds and “stratus” for low-level clouds. So we are using the same word – cirrus — to mean two different things: high and wispy. When we take a closer look, it does make some sense.

Wispy cirrus clouds only occur at high altitudes, so anything high up in the atmosphere will either be cirrus or have “cirro” attached to the front of it. Mid-level clouds are easy as we simply add the term “alto” to the cloud type. Naming low-level clouds works like the high-level clouds, except this time we use the term “stratus” to describe the cloud. For example, low-level cumulus clouds would be called stratocumulus.

Next article we will continue our look at clouds and begin to examine each different type of cloud and what they usually tell us about our weather.

Clouds and their types

HIGH-LEVEL CLOUDS

  • Cirrus
  • Cirrostratus

MID-LEVEL CLOUDS

  • Altostratus
  • Altocumulus

LOW-LEVEL CLOUDS

  • Stratus
  • Nimbostratus
  • Stratocumulus

CLOUDS WITH VERTICAL DEVELOPMENT

  • Cumulus
  • Cumulonimbus

 

About the author

Co-operator contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.

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