Naming the clouds
The cloud names used by weather services today were published by a London chemist in 1803.
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Four Latin words do most of the work
Howard's names describe what a cloud looks like. Cirrus comes from the Latin for a curl or wisp of hair, the thin white streaks high in the sky. Cumulus means a heap, the puffy cloud with a flat base. Stratus means a layer or sheet, the flat grey cloud that covers the whole sky. Nimbus is the rain cloud. A French naturalist, Jean-Baptiste Lamarck, had published his own scheme in 1802, but it was in French and never caught on. Latin, the shared language of science, let Howard's names travel.
Today's ten genera are built from these pieces. Add cirro- for high clouds (cirrocumulus, cirrostratus) and alto-, meaning high, for the middle level (altocumulus, altostratus). Join two shapes and you get stratocumulus, a layer made of heaps. Nimbo- or -nimbus marks a rain cloud: nimbostratus is a thick rain layer, and cumulonimbus is a heap that grows into a thunderstorm. The odd one out is alto-: it means high but describes the middle level, because, as NOAA explains, it marks these clouds as higher relatives of the low stratus and cumulus.
From one man's notes to a world standard
Names were not enough; observers also needed pictures. The WMO's own history of the atlas records that Hugo Hildebrandsson of Uppsala made an atlas of 16 cloud photographs in 1879. An international meteorological conference in Munich in 1891 recommended a shared atlas, and the first International Cloud Atlas appeared in 1896 with 28 coloured plates and text in French, German and English. The World Meteorological Organization was established in 1950 and became a United Nations specialized agency in 1951. It continued work on the atlas. On 23 March 2017, World Meteorological Day, the atlas went online for the first time, free to anyone.
A shared vocabulary matters for safety. A pilot told to expect cumulonimbus ahead, or a ship's officer logging altostratus thickening from the west, is passing on information that any trained reader anywhere can act on. That was Howard's point in 1803, and it is still the job of the atlas.
- 1802: Lamarck publishes a cloud scheme in French.
- 1803: Howard publishes cirrus, cumulus, stratus and nimbus.
- 1879: Hildebrandsson's atlas of 16 cloud photographs.
- 1891: Munich conference recommends an international atlas.
- 1896: First International Cloud Atlas, 28 coloured plates.
- 1951: The WMO becomes a United Nations specialized agency.
- 2017: The atlas goes online on 23 March.
| cirrus | a curl or wisp of hair |
| cumulus | a heap |
| stratus | a layer or sheet |
| nimbus | rain cloud |
| alto- | high, but used for the middle level |
High: cirrus, cirrocumulus, cirrostratus. Middle: altocumulus, altostratus, nimbostratus. Low: stratocumulus, stratus, cumulus, cumulonimbus.
- Who proposed cirrus, cumulus and stratus in 1803?
- Luke Howard
- Jean-Baptiste Lamarck
- Hugo Hildebrandsson
- What does cumulus mean?
- A heap
- A layer
- A wisp of hair
- What does stratus mean?
- A layer or sheet
- Rain
- High
- Which name element marks a rain cloud?
- nimbo- or -nimbus
- cirro-
- alto-
- Alto- means high. Which level do alto clouds belong to?
- Middle
- High
- Low
- How many cloud genera does the WMO atlas recognise?
- In what year was the first International Cloud Atlas published?
- Put these events in order, earliest first.
- Stratocumulus describes…
- a layer made of heaps
- a thin wisp of ice
- a thunderstorm tower
- Why did Howard's names spread more widely than Lamarck's?
- They were in Latin, shared by scientists everywhere
- They were shorter numbers
- Lamarck kept his secret
- Howard (1803) named cirrus, cumulus, stratus and nimbus.
- Ten genera combine these roots with cirro- and alto-.
- First International Cloud Atlas 1896; online since 23 March 2017.
- Shared names let observers anywhere act on the same report.