Wednesday, July 18, 2012

Cumulus Clouds

Cumulus is the Latin word for pile or heap, and cumulus clouds certainly fit their name! They look like fluffy mounds of whipped cream floating in the sky, and often have a shape similar to that of a cauliflower.

 Cumulus clouds form when relatively warm, moist air rises and cools below the dew point. The moisture in it then condenses into tiny water droplets, which form the cloud. The relative humidity (how "full" the air is with water) helps determine the height at which the moisture condenses at, which is the base of the cloud.
In this little video I made, you can see how the clouds form, with the moist air appearing a light mist rising out of the ground. The moist air is not visible in reality, but I added it to help illustrate the idea:

A cumulus cloud constantly undergoes change, as long as moist air continues to rise under it. The water droplets at the edge of the cloud usually evaporate, so the cloud loses water as it gains it. In a time-lapse, the clouds appear to boil.

Here are the main types of cumulus clouds:

Cumulus Humilis

Cumulus humilis clouds are small things with little vertical development. They indicate that the temperature of the atmosphere in the area does not drop very much with altitude, if at all. When seen in the morning, they signify an unstable atmosphere, possibly resulting in thunderstorms.
These clouds are the most likely type of cumulus cloud to be seen during Winter.

Cumulus Mediocris

Cumulus mediocris has a greater vertical development than that of cumulus humilis, but is not as large as cumulus congestus. When these clouds are seen in the morning or early afternoon, they often indicate storms later in the day.

Cumulus Congestus

Also known as towering cumulus, cumulus congestus are tall, towering clouds that often precipitate (rain, hail, etc.). They are similar to cumulus mediocris, but are a lot larger and taller. They often develop from cumulus mediocris clouds, but may develop from other types of clouds as well. If this type of cloud continues developing, it can become a cumulonimbus cloud. The one in the picture above became a small one within a few minutes.

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