Atmosphere And Weather

An Overview on Cloud Formation

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An overview on cloud formation brings to mind something more than the tag clouds in search engine optimization (SEO) of web pages. It brings to mind dancing elephants, skipping children and imaginary playmates floating across the cloudy skies. The image depends on the type of cloud formation that is present. 

Scientifically, there are certain conditions that come together to form various cloud formations.  This determines one cloud type over another. Clouds consist of various cloud colors; what the cloud is made of-a visible mass of water droplets, ice crystals or both; the shape of the cloud-puffy, slightly puffy or completely flat; opaque or transparent; rain consistency; and where is the cloud in relation to the horizon. Clouds form high in the atmosphere or low near the ground, developing in numerous sizes and shapes.

The major cloud formations consist of the:  (1) altocumulus, (2) altostratus, (3) cirrocumulus, (4) cirrostratus, (5) cirrus, (6) cumulonimbus, (7) cumulus, (8) nimbostratus, (9) stratocumulus and (10) stratus. However, these conditions also apply to cloud formation arising from surface heating, by air forced to rise, and due to weather fronts.  

~ Colors of clouds

Different colors of clouds play a role to understand the type of cloud there is. It also demonstrates what is going on deep inside the cloud. Clouds that are characteristically white in color will exhibit a high 70%-95% reflective rate. Known as "dense deep tropospheric clouds," these white clouds are densely packed with water particles. Because of this, light cannot penetrate deep into the cloud before the cloud reflects outward.

Cloud brightness depends on what type of cloud it is, with the color of light reflecting where a person is standing beneath the cloud-and where the person's shadow lies. A bright red sun or major forest fire forms a beautiful red cloud that can be absolutely astounding. And if someone stands under a tall thick cloud, it will appear grayer than when they are standing off from the side. Then it will appear to be white.

Overall, cloud color is processed by the "Scattering" effect. This means clouds are able to scatter numerous wavelengths of light equally, with the visible light spectrum seen in equal sums. According to our brain's response to color, light strikes the color receptors in our eyes with our brain responding to various colors through different light wavelengths. This particular range is called the visible spectrum. Without it, a person could not see cloud color or any other type of color.

~ Characteristics of clouds

Clouds are made of three things-ice crystals, water droplets (considered condensed water vapor or gas) and a combination of both. Floating in the air above sea level, each particle or droplet is tinier than a single grain of flour and light enough to float on air. Clouds are made when these particles come together, causing three conditions to occur: (1) evaporation (lifting), (2) cooling and (3) condensation. When water droplets or ice crystal begin to suspend in the air, different types of cloud formations develop within different levels of the atmosphere.

Regardless of the type of cloud, warm air holds more water vapor than cooler air. Once warm air begins to cool, it cannot hold all the water vapor it originally held. Condensation is when water changes from a vapor or gas to a liquid form. The excess water vapor that cannot be held by the cloud begins to condense into liquid water droplets. This occurs when dust or pollen particles allow the water vapor to condense upon it. In turn, a condensation nuclei is formed. As this occurs in large numbers, a cloud will begin to form. Eventually, the excess water droplets will fall on Earth as rain or snow..

~ Three main groups of cloud formations

The Low Cloud group

The low cloud group consists of the stratus, stratocumulus and the nimbostratus cloud formations. They are made of water droplets alone, and are located approximately 2,000 miles off the ground.

- The stratus cloud covers all or most of the sky and is consistent gray in color. Similar to fog in appearance, it never touches the land as fog does. This type of cloud occasionally is accompanied by a light mist or drizzle.

- The stratocumulus cloud is low, lumpy and grayish in color. At times, each lump lines up in rows or spreads out across the sky. Many times, they are described as having a "cells under a microscope" appearance. Less moisture accompanies the stratocumulus cloud than the stratus-a light drizzle only. The stratocumulus is similar to the altocumulus clouds, but if the cloud is the size of a fist when it is pointed directly toward the clouds, it will be a stratocumulus. The altocumulus will be the size of a thumbnail.

- The nimbostratus cloud is a formless dark gray cloud with a very ragged base, associated with lots of continuous snow or rain. As it builds up, the edges of this cloud sometimes cannot be seen as it usually covers the entire sky. The word "nimbo" is Latin and means rain. A nimbostratus cloud is classified as a low cloud group, but is listed under the middle cloud group when it reaches another 1,000 miles in the air. Typically, its original development is in the middle cloud group. They form from the altostratus clouds before subsiding into the lower range group as snow or rain arrives. When it is in the upper altitude, its precipitation will fall as ice crystals before they melt and evaporate. This is due to increased air pressure as the cloud lowers itself to the warmth of the Earth. Found in the middle latitudes of Earth, the nimbostratus clouds are very thin clouds and are accompanied by separate layers of altostratus, divided by cloudless layers.

The Middle Cloud group

The middle cloud group consists of the altostratus and altocumulus cloud formations, consisting of ice crystals and water droplets. This cloud base is located 2,000-8,000 miles in the air off the ground and 2,000-4,000 miles in the air at the Polar Regions. The prefix "alto" of both cloud types refers to being in the middle.

- The altocumulus cloud formation refers to large gray groups of clouds that appear puffy in appearance. One part of the cloud is usually darker than the other. They are occasionally seen in parallel waves or bands, instead of covering the entire sky in one large cloud formation. When this type of cloud begins to form on a very humid and warm summer morning, by late afternoon thunderstorms will soon be approaching. The altocumulus cloud is often confused with the stratocumulus or cirrocumulus clouds. However, the cirrocumulus cloud will be smaller and less dense. The difference between the altocumulus and stratocumulus is described above under stratocumulus cloud formation.

- The formless layer of the altostratus clouds is grayish or blue-gray in color, usually covering the entire sky. There may be thin areas, where the sun can be dimly seen through the cloud mass. This type of cloud will form in advance of storms with continuous precipitation. The altostratus clouds will thicken into a nimbostratus formation if a warm front is approachin

The High Cloud group

The high cloud group consists of clouds of ice crystals, making up the cirrus, cirrostratus and cirrocumulus clouds in the upper troposphere levels of the sky. The cloud base is located 6,000-18,000 miles in the air off the ground and 3,000-8,000 miles in the air at the Polar Regions. The prefix "cirro" refers to high.

- The cirrus clouds are the most commonly seen of the high cloud group—usually white in color and are predictors of pretty fair weather. They can be seen as icy streamers that are long and wispy in appearance. This streaming cloud effect is because of the high winds in the upper levels traveling from west to east. What is happening is the crystalline structure of the cirrus cloud is being stretched by the excessive winds, causing a "mare's tail" appearance.

- The cirrostratus clouds are sheet-like clouds that cover the entire sky. They are transparent enough to allow the sun or moon to shine through, with possible halos around them. This is caused by the cloud's ice crystals refracting light from the sun or moon. The cirrostratus clouds may arrive 12 to 24 hours before a rain or snowstorm approaches. It is a guaranteed storm if the middle group clouds are also seen with the development. Both the cirrostratus and altostratus are similar in appearance, except that cirrostratus is the only one that projects a shadow upon the ground.

- The cirrocumulus clouds are mainly ice crystals, whitish in color with a few appearing gray. When holding your hand up to the sky, the clouds will be the size of your little pinky finger. They look like small round puffs in long rows, instead of a solid mass throughout the sky. These clouds develop into a "mackerel sky" appearance because the clouds look like the scales of a mackerel fish.

~ Conclusion

This overview of cloud formation has lightly touched on a little bit of everything, hoping to hit the most important aspects of how a cloud forms, what it looks like and what weather it signifies. Clouds play a huge part in forming weather on Earth, better allowing scientists to understand the climate and its probabilities.

New studies and approaches to understanding cloud formation through climate modeling are now being done at the Center for Multi-Scale Modeling of Atmospheric Processes(CMMAP). Through science and technology studies at the Colorado State University, the CMMAP focuses on improving the representation of cloud processes in climate models. It allows for Colorado University studies for primary grades, graduate work and internships for research, education, outreach, diversity and knowledge transfers.

More about this author: Nancy Houser

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