Cloud Clarity

By: Lacy Sellent, Writing Fellow at the Cable Natural History Museum

Like many others, I often catch myself cloud gazing. Some days I can’t help myself.  Days with bright blue sky and fluffy white clouds are the best. I might find myself looking at a rabbit or a mouse—noticing how one part of the cloud looks like a mouth or how other parts looked more like ears.

I always thought it might be fun to be able to name all the different clouds.  I knew a few of the cloud types—cirrus, cumulous, cumulonimbus—but which word goes with each cloud? With so many varieties (all sounding slightly similar), I sometimes felt like I was playing some sort of name game. Then my inquisitive side got the best of me and I decided to do a little research. Here’s what I found.

First, the cirrus cloud. These clouds form high—drifting across the sky at some 18,000 feet. That is more than three miles!  They are mostly made up of tiny ice crystals.  These crystals, like the water droplets that form clouds at lower elevations, are created through the cooling of humid air.  As the humid air cools, the water vapors in the air begin to condense.  Depending on the temperature and humidity, this process may take place at different elevations.  When this happens at higher elevations (10,000-20,000 feet), cirrus clouds are formed.

The cirrus cloud does not produce rain and can be found in the sky on many sunny days.  It is a thin, wispy cloud.  In fact, it is because of its wispy appearance that cirrus clouds have also come to be known as mare’s tails.  Now, whenever I look at a cirrus cloud, I can see the tail of a horse racing across the sky.

Cumulus clouds are big and fluffy and hang much lower to the ground than cirrus clouds. Some can form as low as just 330 feet above the ground. The bottom stays flat while more layers of clouds pile on to create a billowy top. Appropriately, the word cumulus literally means “pile” in Latin.

When a cumulus cloud continues to build higher and higher, it is no longer just a cumulus cloud anymore…it is a cumulonimbus. The top of a cumulonimbus cloud can tower more than 40,000 feet above the ground—that’s over seven miles high. Some cumulonimbus clouds have even reached nine miles in height!  As the cloud continues to build higher, it may eventually come in contact with the winds at higher elevations.  When the cloud meets the wind, the wind blows across the top of the cloud—stretching it out and giving it a flat-topped appearance.  This cumulonimbus characteristic has been dubbed the “anvil cloud”.

Cumulonimbus clouds, especially with anvil tops, are the harbingers of thunderstorms. They possess the power to make windows rattle and to turn trees upside down. With them can come some of the most severe weather in Wisconsin. When a cumulonimbus rolls in, it comes with a presence that demands attention. These are the clouds that give me the greatest feeling of awe.

Whether it is the wispy cirrus, the fluffy cumulus, or the thunderous cumulonimbus, I have come to find that each cloud has something different to offer. Or, to anyone working outside on a sunny day, most any cloud in general may have a great deal to offer. Well, maybe not the cumulonimbus. You might get more than you asked for with that one.