1. What Clouds Are Made Of: Tiny Water and Ice Particles
A white cloud is a collection of countless tiny water droplets and ice crystals floating in the air. Unlike water vapor, which is an invisible gas, a cloud is made of liquid or solid particles. [1]
These particles can grow high in the sky and fall as rain or snow. [1]
2. Why Do Clouds Stay Up? Slowly Falling Particles and Rising Air
Cloud particles are extremely small, a few to a few dozen micrometers across. Their falling speed (terminal velocity) is only a few millimeters to a few centimeters per second. [2]
Rising air currents occur almost everywhere in the atmosphere. When a cloud particle’s terminal velocity and the speed of the rising air balance, the particle cannot descend and appears to stay in the air. [2] Clouds that float in the sky this way come in many shapes. How have people classified and named them?
3. How Luke Howard's Hobby Gave Clouds Their Names
The prototype of today’s cloud classification is a system that the English chemical technologist Luke Howard presented at a meeting of a learned society in December 1802. Howard worked for a pharmaceutical company and was an amateur researcher who kept weather observations as a hobby. [3]
Howard based his system on the naming method that the 18th-century naturalist Carl Linnaeus used for plants and animals, and he classified clouds using Latin, with names such as cirrus, cumulus, stratus, and nimbus. The system was published as a paper the following year, 1803. [3]
4. The Ten Cloud Types: A Shared Worldwide Rule
Howard’s system was refined as observations accumulated and was organized into ten cloud types according to height, shape, and whether the cloud produces precipitation. A revised version was agreed at a meeting in 1929, and the World Meteorological Organization (WMO), established in 1951, continues to use it. [4]
The framework is a division by height. High clouds form at about 5,000 to 13,000 meters (cirrus, cirrocumulus, cirrostratus), middle clouds at about 2,000 to 7,000 meters (altocumulus, altostratus, nimbostratus), and low clouds from near the ground to 2,000 meters (stratus, stratocumulus, cumulus). These heights are only a guide that changes by region, and some clouds, such as cumulonimbus, grow vertically from near the ground to close to the upper levels. [4]
5. Japanese Nicknames for Clouds, Like Scale and Sardine Clouds
Japanese has many informal names for clouds based on how they look. "Urokogumo" (scale clouds), "iwashigumo" (sardine clouds), and "sabagumo" (mackerel clouds) are all other names for "cirrocumulus," which forms in the upper layer, and they are used only to tell apart different impressions of how the clouds look. [5]
"Hitsujigumo" (sheep clouds), on the other hand, refers to "altocumulus," which forms lower than cirrocumulus and is thick enough to have shadows at its base. A well-known way to tell them apart is to hold out your arm and raise your little finger: if the cloud patch is hidden behind it, it is a scale cloud, and if the patch is so large that it sticks out past your index finger, it is a sheep cloud. [5]
6. "Mackerel Sky" and "Fleecy Clouds": Similar Comparisons in Other Languages
Cirrocumulus is called "mackerel sky" in English. Like the Japanese "sabagumo" and "iwashigumo," it shares the idea of comparing the clouds to a school of fish. [6]
Fluffy, wool-like clouds such as altocumulus and cirrocumulus are sometimes called "moutonné" ("fleecy") in French and "Schäfchenwolken" ("little sheep clouds") in German. Exactly which cloud these words refer to varies by language and region, but, like the Japanese "hitsujigumo," the idea of comparing clouds to sheep is shared in several languages. [6]
7. How to Observe and Tell Clouds Apart Yourself
Look up at the sky and think about which height and shape of the ten cloud types the clouds you see belong to. The next time you spot such a cloud, line up the Japanese nickname next to the English and German names. You may find that people in completely different places looked at the same shape and made the same kind of comparison. To tell scale clouds from sheep clouds, try the little-finger method. [5]