Clouds, these white or gray cotton ball masses we often see in the air are a natural phenomenon and an important part of Earth’s weather. Meteorology, from the Greek word “meteoros”, meaning “high in the sky” is the branch of atmospheric science that studies weather and clouds amongst others. Clouds are continually changing, appearing in an infinite variety of forms. Essentially, they are composed of small tiny water droplets or ice crystals, depending on the height of the cloud and the temperature of the atmosphere. A cloud is formed when the water drops and ice crystals settle on dust particles in the atmosphere. These are so small that each cubic meter of air contains a hundred million droplets.
Types of Clouds
Clouds are named in two ways. The first way is by where they are encountered in the sky, high up, low (or at least closer to the Earth’s surface) and somewhere in between. The second way clouds are named is by their general shape.
The following list is a short look on the main cloud types:
High Clouds: 20.000 feet or above
- Cirrus: All high clouds are a type of cirrus. These can be seen at any time of the year. They are layered, tufty or patchy.
- Cirrocumulus: Relatively rare, they form ripples which may resemble honeycombs or fish scales. They are layered or shaped like patches of cells.
- Cirrostratus: Composed of ice crystals, it forms a veil that covers all or part of the sky. Its shape is layered.
Medium Clouds: Between 6.500 and 20.000 feet
- Altocumulus: Normally associated with settled weather. They normally appear white or grey with shading. They are shaped like bands or areas of individual cells.
- Altostratus: They evolve as a thin layer from a gradually thickening veil of cirrostratus and are usually grey or blue in color with very few features. They are layered and featureless.
- Nimbostratus: A thickened altostratus that bears rain. They are shaped like bands or areas of individual cells. They are likely to precipitate continuous rain or snow.
Low Clouds: Below 6.500 feet
- Stratocumulus: They consist of large, rounded masses of stratus that form groups, lines or waves. They have a cumuliform “lump” at their base.
- Stratus: They tend to be featureless, low altitude clouds that cover the sky in a blanket of fairly uniform white or grey color. They can persist for long periods of time.
- Cumulus: Fluffy and cauliflower shaped they are one of the most common and distinctive types of cloud. All cumulus clouds develop as a result of convection. They are detached and individual, and are spotted mostly in fair weather conditions.
- Cumulonimbus: They are also known as “The King of Clouds”. They exist through the entire height of the troposphere, and are usually characterized by an icy, anvil-shaped. Top. They precipitate heavy rain and thunderstorms.
How are Clouds formed?
Clouds are part of the endless water cycle of Earth. A brief, simplified summary of the cycle is as follows: The sun heats the planet’s bodies of water. Some of that water thus evaporates as vapor to the air. Rising air currents take the vapor up, into the atmosphere where colder temperatures condense it into a cloud. Through precipitation, water is released back from the clouds as rain, freezing rain, snow, sleet or hail. And the cycle continues ad infinitum.
So, clouds are made of water vapor which for the most part is invisible – the very air we breathe has some water vapor as part of its composition. Water vapor is made visible through the process of condensation which, to put it as simple as possible, is the following: High temperatures excite water molecules until they change from liquid to a gaseous state. Similarly, low enough temperatures can cause water vapor to condense back into liquid form – in other words, rain.
This small amount stays suspended in cloud form in the air, thanks to small dust particles that it attaches itself to. In the upper reaches of the atmosphere, temperatures are much colder and thus clouds are able to keep their shape longer. The warmer the air is, the more water vapor it is capable of holding.
What causes Clouds to form?
- Surface heating: When the Sun causes the ground to heat, which heats the air contacting it causing it to rise. This tends to produce cumulus clouds.
- Topography forcing: The shape and features of an area can cause clouds to be formed. For example, when air is forced to rise over tall mountains it cools as it rises. Layered clouds are often produced this way.
- Frontal: When masses of warm air rise up over masses of cold, dense air over large areas along fronts – boundaries between warm, moist air and cooler, drier air.
- Convergence: When different streams of air converge, they are forced to rise higher. This can cause cumulus clouds.
- Turbulence: Sudden changes in wind speed with height creating turbulent currents in the air.
The Importance of Clouds
One may be beginning to wonder why would humanity study the nature of clouds so heavily. Clouds are extremely important for a variety of reasons. At night time, they reflect heat and keep the ground warmer. During the day, they make shade that keeps us cooler. They move water vapor around the planet. Water vapor is, in the words of Professor Browning, “a more important greenhouse gas than carbon dioxide”.
Perhaps most importantly, clouds play a key role in climate modeling. The present models of climate change are considered inadequate because they are not currently able to accurately predict how hot the planet will get. Certain models predict a catastrophe, with a temperature increase exceeding 8 degrees Fahrenheit and all the assorted calamities whereas others indicate much more tame responses.
The gap between these predictions is large and stubborn. The answer could be found in the clouds’ role in the environment. What role do clouds play in the grand scheme of things is yet to be uncovered. Will they make the situation worse, or help us escape the worst of climate change?