Ice crystallization is a very important process in clouds like the anvil and other parts of the one below. Most ice crystals that form in clouds will either stay frozen and fall as snow, or it will melt and fall as rain.
Exactly how and why ice crystals form in a "dendritic" pattern is still somewhat of a mystery to physicists. Up until recently the only theory we have had to use is the crystallization theory. Now scientists claim to have found a hypercrystallization process in ice crystals that help them to propagate as much as 10 times the normal rate. We will discuss this later on, first lets take a look at how ice crystals are generally understood to grow.
When we look at continental cumulus clouds, ice is primarially shown to follow the "warm-rain freezing mechanism." In this process raindrops produced by coalescence will freeze near 5 to 10 degrees below zero Celcisus. At these temperatures the drops start to rime, which leads to rapid ice production.
It is not fully understood why the raindrops would freeze at this warm of temperatures since there is such few ice nuclei in the atmosphere. Large atmospheric particles may provide a mechanism for freezing the raindrops. Beard in 1992 showed that typical concentrations of giant nuclei are captured by drizzle drops through direct impaction. This in turn causes the initation of secondary ice production.
This method of ice crystal production still seemed to be slow compared to the speed of nature. The extra speed of growth may be explained through cloud electrification processes.
Origins of Ice Crystals in Clouds
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Last updated 07/22/99 01:31 PM