Tropospheric Names of Clouds
The tropohospheric names of clouds began with two men. The first was Jean-Baptiste Lamarck, who worked on categorizing clouds and cloud formations. However, the names he gave to identify clouds were in French, which failed to gain worldwide acceptance. The names also found little acceptance in France, since the names were unusual names in the French language.
The second man to work on the tropospheric names of clouds was Luke Howard. Because he was already proficient in Latin, he used Latin terms to name the clouds he could identify. A further characteristic of Howard's naming process was that he used the Linnaean taxonomy method of naming the clouds, beginning with genus, species, subspecies, et cetera.
The use of Latin was the main advantage Howard had over Lamarck's tropospheric names of clouds. But by adding the Linnaean classification method, it was more useful to scientists all over the world, and the names Howard used have become the basis of nephology.
Nephology is a branch of meteorology involving the physics of clouds. Because of Howard's more scientific process of giving the tropospheric names of clouds, nephology began with a solid foundation. And adopting the Linnaean method of naming the clouds brought another benefit to the study of nephology.
Early on, Howard recognized the difficulty in identifying clouds, He had already identified three forms, namely the cumulus, stratus, and cirrus clouds, but he also recognized some cloud formations that were in fact a mixture of the three basic cloud formations.
The Linnaean method for tropospheric names of clouds could more easily adapt to such cloud formations. In fact, additions to genus or subspecies could be easily applied using this method. And because nephology was such a young science then (in fact, Howard is considered as the Father of Meteorology), the open-naming system was perfect for nephology.
Cross-identifying Tropospheric Clouds
As the science of nephology matured, more and more clouds were identified and added to the cloud nomenclature. Howard began with three genera of clouds – the cirriform cloud, which he identified as generally being wispy and in pieces, in contrast to the cumuliform, which rolled and heaped in formation, and the stratiform, which are formations that were layered like sheets.
These three types of clouds were crossed over against the altitude in which they appeared. Cumulus cloud was the trophospheric name for cumuliform cloud found in the low levels of the atmosphere, while cirrocumulus cloud was the name given to the cumuliform cloud found in higher heights. Similarly, stratus was the name for stratiform clouds in the low levels, and cirrostratus for the stratiform clouds in the high altitudes.
For all cloud formations that involved precipitation, Howard added the nimbus classification.
Later Additions to the Cloud Formations and Classifications
Around 1840, Ludwig Kaemtz from Germany added the stratocumulus cloud. The year 1855 saw the addition of altocumulus and the altostratus by Emilien Renou. The last two additions were physically similar to the stratocumulus, but were found to occur just as frequently between the upper and lower heights that Howard had previously defined. This discovery created the need to introduce the middle level for cloud classification, instead of being just a higher and lower level of clouds with regard to their altitude.
In 1880, Philip Weilbach introduced a new type of cloud called the cumulonimbus cloud, and its main difference from the cumulus cloud and nimbus cloud was its ability to produce thunder. When this addition was accepted by the meteorological community then represented by the International Meteorological Committee, some changes were needed in Howard's original designs for the tropospheric names of clouds.
The Current List of Cloud Genera
Today, the World Meteorological Organization has the final list of cloud genera, its species, varieties, and supplementary features.
The cloud genera are as follows, according to decreasing altitudes:
- Cirrus Clouds, abbreviated as Ci. Cirrus Clouds are considered high-level clouds, in the range of about 3 to 18 kilometers above sea level. This type of cloud is generally wispy or curly, from the Latin word cirro, meaning mare's tail.
- Cirrocumulus Cloud (Cc). Cirrocumulus Clouds are a cross between cumulus clouds and cirrus clouds, with the wispy characteristic on the ends of a cirrus cloud, and the puffy cotton ball appearance of a cumulus cloud. Also considered in the high level range.
- Cirrostratus Cloud (Cs). The cirrostratus cloud has both the characteristics of a cirrus cloud with the wispy tails, and the stratus cloud, with the horizontal layers. It is also a high level cloud.
- Altocumulus Cloud (Ac). The altocumulus cloud is a middle level cloud with characteristics of a cumulus cloud. Middle level clouds are located in the 2 to 4-kilometer range above sea level.
- Altostratus Cloud (As). The altostratus cloud is a stratus cloud in the middle level range. It is characterized by the sheet-like appearance of the stratus cloud.
- Nimbostratus Cloud (Ns). The nimbostratus cloud is another middle level cloud with the appearance of a stratus cloud and a nimbus cloud.
- Stratocumulus Cloud (Sc). Layered, puffy-looking clouds in the low level range, which is from 0 to 2 kilometers above sea level.
- Stratus Cloud (St). The stratus cloud is another low level cloud that is distinctly layered horizontally.
- Cumulus Cloud (Cu). The cumulus cloud is a puffy-looking cloud, also located in the low level range.
Clouds Above the Troposphere
All of the above clouds occur naturally inside the troposphere. However, certain conditions such as volcanic eruptions can produce cloud formations above the troposphere, or in the lower stratosphere, which is in the 15 to 30 kilometer range. These clouds are called nacreous clouds.
Nacreous clouds are too thin to be visually confirmed from the ground. In the 1991 Mt. Pinatubo eruption in the Philippines, the nacreous clouds that were formed were continually reported by airline pilots midflight at either dusk or twilight. A more common occurrence is when strong winds approach a mountain range, such as the Rockies. The resulting nacreous clouds from the impact of winds against a mountain range is often a visually stunning sight.