There are nine different varieties of clouds that you can identify by their appearance. These varieties are:
1. Opaqus: This is a sheet, a layer or a patch of clouds; the major portion of which is dense enough to obscure the sun or the moon.
2. Perlucidus: These clouds consist of patches of opaqus clouds with breaks that show the blue sky or the sun during the day or through which you can see the moon at night.
3. Translucidus: This is a sheet, a layer or patch of clouds that is not dense enough to obscure the sun or moon. Thus the cloud cover is translucent and you can still see the sun or the moon through the clouds.
4. Duplicatus. This variety of cloud consists of two layers or sheets of clouds that overlap each other at different levels in the atmosphere.
5. Undulatus. In this variety of clouds there are elements or cells in the sheet, layer or patch of clouds that are arranged in parallel rows. They form a wavelike pattern in the sky that tends to resemble the waves of the ocean. Other names for this type of cloud include billow clouds, wave clouds and wind row clouds.
6. Radiatus. In this cloud pattern, the cloud elements arranged in rows merge together so that there are parallel bands of clouds. The straight bands tend to merge together close to the horizon because of the effect of perspective. One of the names for this type of cloud is Abraham’s Tree.
7. Lacunosus. There are rounded holes in this cloud pattern that look like a honeycomb or a net.
8. Intortus. The filaments of the clouds seem to become entangled creating a curved or zig-zag pattern.
9. Vertebratus. The fibers of the clouds are elongated resembling the vertebrae of a fish skeleton.
Clouds can be divided into two general categories layered and convective according to the altitude. Clouds also have different names whether they are high, middle or low clouds.
High Clouds:
1. Cirrocumulus clouds usually occur at altitudes of 16,000 to 40,000 feet. They are small white tufts without any shadows of gray. They sometimes occur in sheets or layers, but can occur in patches.
2. Cirrus clouds have thin, wispy strands and are often accompanied by tufts, which gives them the name mare’s tails.
3. Cirrostratus clouds are thin and usually uniform clouds that occur above 20,000 feet. When they are thick enough to see, they are white and do not have any distinguishing features.
Middle Clouds:
1. Altostratus clouds are generally gray and uniform in a sheet or layer. You can see the sun shining through and they usually cover the whole sky.
2. Altocumulus clouds occur in rolls or patches and are usually white or gray. They occur in sheets or patches with wavy masses or rolls.
Low Clouds:
1. Cumulus clouds are puffy and look like cotton balls. They may appear alone or in lines or sometimes in clusters.
2. Stratocumulus clouds appear in dark rounded masses in groups or lines below 2400 feet.
3. Nimbostratus clouds are the formless clouds that produce rain. They block a great proportion of the sunlight because of the dense structure.
4. Stratus clouds are flat and range from grey to white in color. They are essentially above ground fog from which you may have drizzle of fog.
