There are ten types of cloud
The core idea stands, but key numbers or details have changed.
TaughtClouds come in ten genera: cirrus, cumulus, stratus, and the rest. Learn the chart on the classroom wall, because it is fixed.
NowThe World Meteorological Organization's International Cloud Atlas added twelve new classifications in March 2017, including asperitas, the first new formation added in over half a century, and volutus, cavum, and the human-made flammagenitus and homogenitus.
What actually happened
The International Cloud Atlas is the official reference, and before 2017 its previous full revision was in 1975, with roots going back to 1896. The chart on your classroom wall was, in effect, a nineteenth-century document.
Asperitas is the striking one: a chaotic, wave-tossed underside that looks like the sea viewed from below. It was pushed into the Atlas by the Cloud Appreciation Society, a group of amateur enthusiasts founded by Gavin Pretor-Pinney, who collected photographs from members and campaigned for over a decade. It is the first new cloud formation accepted since cirrus intortus in 1951, and it got in because amateurs with cameras built the case.
Some of the additions record our own footprint. Homogenitus covers clouds formed by human activity, including contrails, and homomutatus covers natural clouds altered by them. Flammagenitus is the pyrocumulus that rises above wildfires, a category that has become considerably more relevant since. The 2017 edition was also the first published online rather than as a book.
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Sources
- WMO: International Cloud Atlascloudatlas.wmo.int
- WMO: New edition of International Cloud Atlas (2017)cloudatlas.wmo.int
Who was taught this
Still standard through 2017, so anyone who finished school between 1950 and 2017 learned the earlier version.