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Alps and Cloud Formation
Name: Timothy
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
We were watching a high peak in Alps on a clear, bright
day. The sun shining on the snowy peak seemed to be creating clouds,
which would gather around the peak, then float away while still
holding their shape. It was not steam or snow and there were no
other clouds in the sky. This went on for over an hour. Can actual
clouds be formed this way and if so, is there a name for this phenomenon?
Replies:
Hi Tim
"Sun shining on snow creating clouds"
Could be the process of "Sublimation"
http://en.wikipedia.org/wiki/Sublimation_(chemistry)
That is where solids, such as ice, directly pass to the gaseous state.
or it could just be melt water being evaporated in the direct rays of the
Sun.
Clouds are visible water vapor.
(Humidity is invisible water vapor)
So the clouds you saw were water vapor rising from the snow field.
Is there a name for this cloud formation technique?
My meteorological training comes from Navy flight training
And I have not heard of a name for this cloud formation technique.
Maybe a professional meteorologist can ferret a name from a text book
somewhere.
I am tempted to add that the formation of fog is somewhat similar to this
process
Provided the water vapor comes from the ground and does not come from the
air.
But I imagine this is a quite common process.
Sincere regards,
Mike Stewart
Timothy,
The mountain peak apparently acted as an obstruction to air flow,
causing air to be forced upwards at the top of the mountain. As air
is lifted it cools, and, if there is sufficient water vapor, it will
condense and form a cloud.
Sublimation of snow (direct ice to water phase transition) to water
vapor by the bright sunshine, combined with lifting of the air,
producing condensation and clouds, appears to be the mechanism
for what you saw.
Since you said that the clouds formed "around" the peak, then floated
away while holding their shape, I must assume that periodically the
wind speed increased enough to blow the clouds away.
What you saw was different from a banner cloud produced by a mountain
peak, as those form in the lee of the peak in relatively high wind speeds.
What you observed was apparently produced during mostly low wind
speed conditions.
David R. Cook
Meteorologist
Climate Research Section
Environmental Science Division
Argonne National Laboratory
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Update: June 2012
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