Cloud Classification
On Wednesday, we discussed the basic mechanism by which clouds develop - water vapor condenses onto cloud condensation nuclei in a process called heterogeneous nucleation. Another important point we developed is that a cloud formed at th e ground level is called fog. Clouds that form aloft have formed because air was lifted to a level where its dewpoint temperature was reached. We call this level the Lifting Condensation Level (LCL)
In coming weeks, we will be discussing the various mechanisms that lead to vertical motion which in turn promotes cloud and precipitation development. Today however, we will be focusing on how clouds are classified and named and we will defer a detail ed discussion of the mechanisms that lead to the development of individual cloud types to future lectures.
Preview of lifting mechanisms
These and other mechanisms of vertical motion will be discussed at great length in coming weeks.
Cloud naming system
Clouds are classified in general by two features: the height at which they are located and their texture. Clouds that take on a "puffy" or "fluffy" appearance are termed cumulo type clouds whereas more uniform flat clouds are termed strato type clouds.
Cloud levels
| Level | Elevation | Prefix |
|---|---|---|
| Low | 0 - 6,000 feet | None |
| Middle | 6,000 - 20,000 feet | Alto |
| High | above 20,000 feet | Cirro |
Clouds at the middle level are given the prefix alto. Clouds at the high level are given the prefix cirro. Cirro type clouds are actually so high up in the atmosphere that they are composed entirely of ice crystals instead of liquid clo ud water droplets. Clouds at the low level are not given a prefix.
The texture of a cloud and the level the cloud is at determine the full name of the cloud. For instance, an altostratus cloud is a middle level cloud that has a flat and uniform type texture.
Precipitating clouds
Clouds that are generating precipitation often contain the word nimbus or the prefix nimbo which is the latin word for rain.
In this lecture, we will basically be studying 10 of the more primary cloud formations. To help you along, I have put this cloud chart online for you. Click here to bring the chart into view, then cli ck on each of the cloud types for a discussion of each one.
During the coming weeks, we will be expanding greatly on these 10 cloud types and you will get a good sense for which types of conditions promote the development of each cloud type. You will see that different clouds can form in a very large number of different and interesting circumstances.