Cumulus cloud
From Wikipedia, the free encyclopedia
 |
This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (August 2008) |
| Cumulus Cloud | |
 |
|
| Abbreviation | Cu |
|---|---|
| Genus | Cumulus (heap) |
| Altitude | Base below 2,000 m (below 6,500 ft) (tops vary) |
| Classification | low-level (family C) or vertical (family D), depending on size |
| Appearance | puffy |
| Precipitation cloud? | Depends. Cumulus humilis and mediocris, most likely no, but congestus, sometimes yes. Cumulonimbus, yes, but may be virga. |
A cumulus cloud is a type of cloud with noticeable vertical development and clearly defined edges. Often described as "puffy" or "cotton-like" in appearance, cumulus clouds may appear alone, in lines, or in clusters. Cumulus clouds are often precursors of other types of clouds, such as cumulonimbus, when influenced by weather factors such as instability, moisture, and temperature gradient. Cumulonimbus clouds may be associated with phenomena such as landspouts, waterspouts and tornadoes. Cumulus means "heap" or "pile" in Latin.
Contents |
[edit] Formation
Cumulus clouds typically form when warm air rises and reaches a level of comparatively cool air, where the moisture in the air condenses. This usually happens through convection, where a parcel of air is warmer than the surrounding air.[1] As it rises, the air cools at the dry adiabatic lapse rate (approximately 3°C per 1000ft or 1°C per 100m), while the dewpoint of the air falls by 0.5°C per 1000ft.[citation needed] When the temperature of the air reaches the dewpoint, some water condenses out of the air to form the cloud. The size of the cloud depends on the temperature profile of the atmosphere and the presence of any inversion. If the top of the cumulus cloud reaches above the freezing level in the atmosphere, then rain from the cloud is possible. If the top of the cloud is below freezing level, then snow is possible.[clarify]
In windy conditions, the clouds can form lines (cloud streets) parallel with the wind.[2] In mountainous areas, they may also form lines perpendicular to the wind due to the presence of lee waves above the clouds.[citation needed]
Over the sea, cumulus clouds may be found in regularly spaced lines. The best examples of these lines are found in the trade winds, where they may extend for many miles. Such lines create a pattern in the vertical movement of air, causing it to roll horizontally. Between the lines of cloud are stronger, more gusty, and slightly veering winds, but beneath the lines of cloud, somewhat lighter and more backing winds prevail.
The height at which the cloud starts to form (cloud base) depends on the amount of moisture in the air parcel that forms the cloud. Humid air will generally result in a lower cloud base.[3] In temperate areas, the base of the cumulus clouds is usually around 8,000ft (2,400m) in altitude. In arid and mountainous areas, the cloudbase can be in excess of 20,000ft (6,000m).
Glider pilots often pay close attention to cumulus clouds, as they can be good indicators of rising air drafts or thermals underneath. [2]
[edit] Forecast
 Cumulus mediocris clouds above Rainbow Ridge in Red Rock Canyon, Las Vegas, NV. |
 Cumulus congestus cloud |
Cumulus clouds, appearing as small- or medium-sized puffy shapes in the sky, often occur in times of fair weather.[4] However, cumulus clouds can grow into cumulonimbus clouds which may produce heavy rain, lightning, severe and strong winds, hail, and even tornadoes.[5] [6] Cumulus congestus clouds, which appear as relatively thin towers, will often grow into Cumulonimbus storm clouds.
[edit] References
- ^ "BBC - Cumulus Clouds" (in English). Retrieved on 2008-08-15.
- ^ a b "Pilot Outlook - Cloud Streets" (in English). Retrieved on 2008-08-13.
- ^ "ARIC - Cumulus Clouds" (in English). Retrieved on 2008-08-16.
- ^ "Michigan Tech - Cumulus Clouds" (in English). Retrieved on 2008-08-13.
- ^ Palmer, Chad. "USA Today - Cumulus Clouds" (in English). Retrieved on 2008-08-13.
- ^ Thompson, Philip; Robert O'Brien (1965). Weather. New York: Time Inc., 86-87.
[edit] See also
[edit] External links
- AMS Glossary of Meteorology
- Cumulus cloud at BBC Weather
- Cumulus cloud page at University of Richmond internal site
- Time-lapse of the formation of Cumulus clouds
|
|||||||||||||||||
