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Clouds & How They Form

Updated: Wednesday, August 14 2013, 11:28 PM EDT

Clouds are made of ice particles and water droplets and are suspended in the atmosphere. While cumulus, cirrus, and stratus clouds are most common, some clouds have unique names or are a blend of cloud types.

Cumulus clouds over the Cincinnati/Northern Kentucky International Airport

Clouds in the atmosphere form as a result of air cooling and condensing. When radiation – or energy – from the sun strikes the Earth’s surface, it warms it. This warming of the ground, in turn, causes the air in contact with the ground to warm; relatively warm air rises in the atmosphere, but it also cools as it rises. As air cools, it eventually reaches temperature (called the dewpoint) where it condenses. In other words, water vapor becomes a liquid or solid once the temperature of a bubble of air reaches it’s dewpoint. When air cools below it’s dewpoint, a cloud forms. Clouds that form this way are typically cumulus clouds and take on a cauliflower-like shape. Cumulus clouds form where instability is present and can extend hundreds of feet up into the atmosphere.

Stratus clouds over downtown Cincinnati

Stratus clouds – which are flat-shaped, close to the ground, and often grey – form as a result of warm, humid air rising up and over cooler, drier air.  Stratus clouds take up more space horizontally than they do vertically.

Cirrus clouds over downtown Cincinnati

Cirrus clouds are thin, wispy clouds made of ice crystals in the upper-levels of the atmosphere. The anvil-shaped clouds at the tops of thunderstorms are a type of cirrus cloud. Cirrus clouds are often the first type of cloud to move into an area when a developed area of low pressure is approaching.

Cumulonimbus cloud over Clermont County on July 4, 2012

Prefixes are often added to the cloud names mentioned above; these prefixes help to describe the texture of the cloud, the altitude of the cloud, or what the cloud does. For example, a stratus cloud that produces steady rain or snow over a wide area is called a nimbostratus cloud (nimbus means “rain”). The prefix “alto” (as in “altostratus” or “altocumulus”) means a cloud is in the mid-levels of the atmosphere (between 8,000 and 20,000 feet). The prefix “cirro” (as in “cirrostratus” or “cirrocumulus”) means a cloud is in the upper-levels of the atmosphere. Common in the Tri-State during the summer, cumulonimbus clouds are clouds associated with a thunderstorm that extends hundreds or thousands of feet vertically in the atmosphere.

Sometimes clouds form as air is forced up a mountain slope, along a sea breeze, or an outflow boundary left by a dying, nearby thunderstorm.

Clouds come of shapes and sizes and form in a variety of ways. When you look up into the sky next, see what clouds have formed; the type of clouds you see will likely give you clues about how they formed and may help you figure out what weather is on the way.

Clouds & How They Form

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