This topic is about what nature does that prepares all
of the elements for the making of snow.
High up in the sky clouds begin to form. Clouds are
made of water vapour. The temperature is cooler up in the clouds than it is on
the ground as a general rule. However, the temperature is not constant
throughout the clouds. There are different layers or zones of temperature.
These different temperature zones play an important role in the forming of a
snow flake or crystal.
The water vapour in the clouds is being blown around
by winds through the different temperature zones. Typically liquid water will
freeze at approximately 0°C. However, for water to become solid (freeze) the
water molecule (H2O) needs to slow down and to touch something solid. By
touching something solid and slowing down the water molecule can, under normal
circumstances transition from a vapour/gas to a liquid to a solid, or from a
vapour to a solid directly. But up in the cloud there is mostly water vapour
(very few solids) and lots of movement. So the water molecules continue to cool
while still in a vapour form. This is called super-cooling.
When a water molecule is in a super-cooled state it
can go from a vapour/gas to a solid quickly and directly. So what it mostly
needs now is something solid. The "something solid" is called a
nucleator. Most commonly the nucleators found in clouds are dust. The
nucleators are very, very small. Small enough that the winds can lift them high
into the sky. Small enough that you can't see one with the naked eye. The job
of the nucleator is to start the snow crystal. Once the crystal is started then
other water molecules can join onto this crystal.
Eventually after blowing around for a period of time a
water molecule will join with a nucleator. The process of building a crystal
has started. Other water vapour molecules in their super-cooled state will find
this crystal. Some of these molecules will join the crystal and some will not.
The process of building a crystal is slow.
How a crystal grows is determined mostly by the amount
of water available (the super-saturation level of ice relative to water in air;
we'll call this the "SSL(I)" for personal typing sanity) and the
temperature with an influence by the atmospheric pressure and (it seems)
possibly the electrical charge. Once the crystal starts it is still subjected
to the same forces that the water vapour molecules are subjected to. The
crystal is blown around throughout the cloud through a variety of different
temperature zones. The crystal can continue to be blown about for tens of
minutes to hours before falling to the ground. At different temperatures fresh
water molecules will attach to the crystal at different locations. In other
words the crystal will "grow" differently at different temperatures.
Since the crystal is being subjected to a variety of temperatures and
humidities as it is blown about, the crystal will grow differently at different
times.
source : www.skiwax.ca/tp/snow.php
1 komentar:
In my opinion, the explanation about how snow is made is rather complex. It needs an high comprehension to know how snow is made in detail.
Based on the explanation above,I can conclude that snow happens when rain freezes while falling. That's why when it is snowing it's always cold, otherwise the rain would not freeze into snow while in the air.
When the snow fall, we can find all the shoveling and dirtiness of old snow, but it has wonderful insulating values for plants, keeping tender roots from freezing out. On top of that, snow hides the all the browns and grays of winter that maybe can be depressing.
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