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First Snow.... Name the date :)


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I was bored Wolfie. I don't suppose you happen to know any scienticic formula's or statistics associated with snow do you :wink::lol:


A systematic way to examine

the origin of variety in falling snow. First, we define shape

diversity as the logarithm of the number of possible distinguishable

crystal forms for a given resolution and set of conditions,

and then we examine three sources of diversity. Two

sources are the range of initial-crystal sizes and variations in

the trajectory variables. For a given set of variables, diversity

is estimated using a model of a crystal falling in an updraft.

The third source is temperature-updraft heterogeneities

along each trajectory. To examine this source, centimeterscale

data on cloud temperature and updraft speed are used

to estimate the spatial frequency (m−1) of crystal feature

changes. For air-temperature heterogeneity, this frequency

decays as p−0.66, where p is a measure of the temperaturedeviation

size. For updraft-speed heterogeneity, the decay is

p−0.50. By using these frequencies, the fallpath needed per

feature change is found to range from 0.8 m, for crystals

near −15C, to 8m near −19C – lengths much less than

total fallpath lengths. As a result, the third source dominates

the diversity, with updraft heterogeneity contributing more

than temperature heterogeneity. Plotted against the crystal’s

initial temperature (−11 to −19C), the diversity curve is

“mitten shaped”, having a broad peak near −15.4C and a

sharp subpeak at −14.4C, both peaks arising from peaks in

growth-rate sensitivity. The diversity is much less than previous

estimates, yet large enough to explain observations. For

example, of all snow crystals ever formed, those that began

near −15C are predicted to all appear unique to 1-μm resolution,

but those that began near −11C are not.


The deposition of water vapor in air produces crystals with a

surprising degree of variety, symmetry, and intricacy. Formation

of various intricate features have been studied onand-

off over the years (e.g. Nakaya, 1954; Yamashita, 1976;

Frank, 1982; Hallett and Knight, 1994; Nelson, 2005), and

the symmetry is now understood to arise from the growth

mode (Frank, 1982), but the sources of snow crystal variety

have not been examined systematically.

The variety is generally equated to the number of possible

crystal forms, a quantity that has been estimated through two

approaches. The first approach is to estimate the number of

possible distinct crystal forms for a given crystal radius (e.g.

Knight and Knight, 1973). However, this approach yields no

insights into the origin of the variety and it does not include

limitations from the growth process; in particular, we neither

learn the role of the crystal-growth response to the environment

nor do we see how this response may limit the types of

crystal forms. A different approach was suggested much earlier

by Bentley (1901) when he wrote that the various crystal

features originate from the various “atmospheric layers” the

crystal falls through1. As a preliminary step in this direction,

Hallett (1984) used knowledge of the crystal response to estimate

the variety. His result, about 1030 000, is immense (and

much less than the 103 000 000 of the first approach), but the

method involved guessing the crystal’s environment. Now,

we still do not know if crystals pass through

enough “layers” (regions) to produce the observed variety,

or even if those layers are the main source of variety.



Of course this only applies if you are driving at 20mph. :wink:

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<_<:lol: 10/10 for effort Evils but alas only 1/10 for content as that is not a formula but was very interesting all the same. :wink:


How do the figure that out though as every snowflake is unique and they break up and change all the time as they fall and reform :unsure:

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Damn, overlooked again. :angry: :angry:


OMG Wolfie I am so sorry and I knew it was you and you were the one I was replying to hence my winks etc so god knows why I types Evils :oops: I can only imagine that it was because the previous post was by Peter and he made me think 'evil', or the fact that your wolf howling makeds me think 'evil; or perhaps my mind was still on the 20 theme :wink::oops:


I hope one day you will forgive me :(:( but hey poor Evils getting mistaken for you eh as that must be worse :lol::wink:

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