Clouds

How Clouds Form
 
    A cloud is a visible aggregate of minute water or ice particles suspended in air.  Clouds form when warm rising air and water vapor pools, cools, and condenses .  The possible reasons why this happens could be one or more of the following:  (1) warming of the air at the earth's surface (convection) (2) air cooling as it expands, such as when wind encounters a mountain and moves up side (3) activity at a front or low pressure system (4) air expanding and cooling, such as when the rising air is exposed to lower pressure. However, cool air cannot support as much moisture as warm air. Therefore warm air that is rising will cool and reach a point whereby its relative humidity is 100% .  It is at this point that moisture begins to condense onto the surface of particles in the atmosphere, such as tiny dust particles, soot, salt, and sulfate. These particles act as cloud condensation nuclei (CCN). Studies show that the more condensation nuclei in the atmosphere, the thicker the clouds will form.

A "Cloudy" Connection to the Future Climate
    Clouds are a great source of uncertainty in predicting future climate. Everyone is aware of clouds, but not everyone is  aware of the importance of clouds to weather and climate, and especially the role that clouds play in global climate change.  Clouds are the source of precipitation, a factor that influences the amount of energy from the sun that earth absorbs, and insulates the earth's surface and lower atmosphere.  At any given time, a considerable portion of the earth is shadowed by clouds.  Clouds reflect and absorb some of the sunlight away from earth.  Clouds reflect sunlight back to outer space (tending to cool the climate) and also absorb infrared radiation from the earth (tending to warm it). Which effect dominates depends on the clouds' brightness, height, distribution, and extent.  Scientists are not sure which cloud type might predominate or how this factor would vary in different parts of the world. At this particular time there are more questions than answers. Much more research remains to be done.
 

Other Cloud Activities

• Cloud Type Protocol
• Cloud Cover Protocol
• Observing, Describing, and Identifying Clouds
• Cloud Watch

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