"No two snowflakes are alike."  BUT, they definitely do come in shapes and sizes that can be categorized so that we can study their formation.  The picture-link to the right shows one of the early catalogs of snowflake shapes, produced by Ukichiro Nakaya, an early photographer of snow crystals. [1]  Almost all snowflakes can be categorized as one of these types, or as a mixture of these types.
 

When looking at all of the different shapes that snowflakes can take, it's easy to imagine that they might grow under very different conditions...  So the purpose of our project became to model only the dendritic shapes.  But just for fun, let's talk about why there are so many different shapes for a minute.
 

The next image helps show what's going on.  Imagine a snow crystal in the process of forming.  It's blowing around inside a cloud, most likely, and passing through all sorts of different conditions, including varying temperatures and levels of supersaturation.  Scientists have determined that the different types of crystal formations happen depending on what the temperature and supersaturation values are, as shown in the graph at right. [2]
 

You can see that, if the particle is in a cloud, most likely its supersaturation level will follow the water saturation line on the graph.  After all, that's what a cloud is!  So as temperature decreases, you get thicker and thicker "plates."  The plates refered to are hexagonal prisms, and for the interests of this project, we'll talk about very flat prisms which approximate two-dimensional hexagons.
 

The motion of the particle through the cloud often raises the effective supersaturation level, though, and so at around -15 degrees the flat hexagonal "seed" starts to undergoe dendritic growth, eventually turning into something that looks like the last picture. (Check out the tiny crystal that landed on the top left of the big one.)
 

These are called "dendrite crystals," and are the subject of our computer simulation. 
 

MAIN PAGE    SNOWFLAKE SHAPES   DIFFUSION

OUR SPIFFY MODEL OF DENDRITIC GROWTH

OUR HOT APPLET OF DENDRITIC GROWTH

THE RESULTS OF OUR HOT APPLET OF DENDRITIC GROWTH

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