Heavy and light H2O

snowflake3According to Richard Alley in The Two Mile Time Machine ‘heavy’ water is rare (for every 6,000 parts of water, there is only one part that is heavy water.)

Rain and snowflakes are formed from water vapour from the heavier isotopes of H2O. Water has an atomic weight of between 18 to 22.

Not being all that knowledgeable about snow, a little reading turned up some interesting facts I thought I would share;

“What are common snowflake shapes?

Generally, six-sided hexagonal crystals are shaped in high clouds; needles or flat six-sided crystals are shaped in middle height clouds; and a wide variety of six-sided shapes are formed in low clouds. Colder temperatures produce snowflakes with sharper tips on the sides of the crystals and may lead to branching of the snowflake arms (dendrites). Snowflakes that grow under warmer conditions grow more slowly, resulting in smoother, less intricate shapes.





  • 32-25° F – Thin hexagonal plates
  • 25-21° F – Needles
  • 21-14° F – Hollow columns
  • 14-10° F – Sector plates (hexagons with indentations)
  • 10-3° F – Dendrites (lacy hexagonal shapes)”

Source: http://chemistry.about.com/od/moleculescompounds/a/snowflake.htm

I don’t believe I am any more able to identify the temperature at which the pictured snowflake was formed. Perhaps someone could help me out? If identifying snowflake temperature is good fun, here are some more from [Alaska…http://www.andysorensen.com/Nature/Snowflakes/Alaska-Snowflake-Photos-1/2309403_oBP6E#120860351_Zvrth]

So to get to the crux of things – is snow flake biodiversity endangered by global warming?

1 thought on “Heavy and light H2O

  1. Christine

    ps. The temperatures listed are cloud temperatures at rather than ground temperatures. At a cloud height of 1.25km the temperature is 8 degrees C (46.4degF) and at 11.25 km the temperature is -57 degrees C(-70.6degF).

    According to Wagner et al in their paper ‘Dependence of cloud fraction and cloud top height on surface temperature derived from spectrally resolved UV/vis satelite observations(2007)'[abstract]

    “Cloud climate feedback constitutes the most important uncertainty in climate modelling,
    and currently even its sign is still unknown. In the recently published report of the intergovernmental panel on climate change (IPCC), from 20 climate models 6 showed a
    positive and 14 a negative cloud radiative feedback in a doubled CO2 scenario.”

    Reply

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