Chitika

fredag 11 september 2009

Frontal Weather Systems Result From Lifting Clouds

By Leroy Calstard

Classifying Clouds The infinite array of majestic clouds delights us and have, ever since humankind claimed their place on the earth. You are likely aware that clouds are a gas and simply evidence of lifting air masses. Rain from the clouds is just condensing water vapor. Meteorologists interpret future weather using cloud shapes. Did you know that the system for documenting clouds was created in the early 19th century?

Luke Howard, weather scientist developed a classification scheme in 1803. Using the language of science - Latin - Howard documented the basic cloud shapes. His writings allowed for words to be combined which enabled deeper classification. His system was immediately accepted and universally admired. This is a system for tracking weather systems.

According to this system there are two basic types: Cumuliform and Stratiform. The Cumuliform is taken from the Latin word cumulus. That word means 'heap.' Cumuliform are puffy clouds. This kind is usually made from convection or orographic lifting. The next type, Stratiform is taken from the Latin word stratus that means layer. Stratiform clouds have a flat, layered shape. Frontal weather systems result from lifting clouds. These Stratiform clouds lift in a uniform manner. Stratiform clouds are associated with stable weather.

These two basic kinds are further classified in height. High-level clouds (those above 16,500 feet) are named cirrus clouds. Periodically the prefix cirro, will be tacked on to a basic cloud type. Cloud formations between 6,500 and 16,500 feet always have the prefix alto. On the other hand, cloud formations below 6,500 feet do not have prefix. These remain basic names such as stratus or cumulus by default. Luke, by combining height prefixes with basic kinds, described several kinds of clouds such as the altostratus. Then there is the familiar cumulonimbus cloud. That's the one that can over time develop into a thunderhead. Although not an exact science, clouds are a flexible classification system.

Precipitation Warm air rising is what causes clouds to form. Any cloud is saturated with water vapor. Water vapor condenses into tiny droplets of water, or sublimates into tiny ice crystals. When these droplets or ice crystals gain weight, gravity tends to pull them down toward the ground. This is generally regarded as rain, snow or other precipitation. What type of precipitation falls determines how it is all classified? Whether precipitation falls as rain, freezing rain, sleet, or snow it all depends on the processes of formation, temperatures within the cloud, temperatures below the cloud, and ground temperatures.

Precipitation might be called rain, fine mist, or a drizzle. It all depends upon the moisture drop size. Rain or snow may also be called steady or intermittent. Steady precipitation is usually associated with weather changes and activity, while intermittent precipitation is more likely to be associated with convection and atmospheric instability.

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