flying into snow showers without deice

"Matt Whiting" wrote in message
...
Mike Rapoport wrote:

"Matt Whiting" wrote in message
...

Peter R. wrote:


Matt Whiting wrote:



So, part of the flake is still below freezing and part is above.


Is that really possible?

Sure, just as it is possible for water to be below 32F and not frozen.


Matt


No. The difference is that the snowflake is *melting*. If you cool
water, it will go below 0C before freezing but ice will *not* melt below
0C (at normal pressures).

I never said it would melt below 0C. I said it is possible that the
frozen part of the flake could absorb enough energy from the liquid part
to refreeze it.

For this to happen the water has to be supercooled. You don't get
supercooled water from melting ice. The only way that you can get
supercooled water from melting ice is to "melt it" with pressure.

Did you ever put ice in a glass and then add some water and have the ice
cubes bond together? Same idea. If you don't believe that ice can
extract enough energy from water to refreeze it, how do you explain this?

Yes, I have seen this happen but it is not the same as what you are
describing. If you take a very small-thin piece of ice and allow it to
start melting it will not then freeze to anything that is above freezing. It
works with larger chunks if ice because the core temp can be significantly
lower than the surface temp. This in not true for snow.


Keep in mind that ice doesn't have to be at 0C. The temperature of ice
can be much lower than 0C and thus it can absorb a fair bit of energy from
its surroundings before melting.

Yes, but in the case of snow which has a lot of surface area and little
volume, the flake will not have big differences in temp from one part to
another. I don't know if you are familiar with the concept of "latent hear
of fusion" but basically to convert water at 0C to ice at 0C requires a LOT
of energy to be removed.

Mike
MU-2