Decent into Cleveland

Thank you. Makes sense.

In my little experience, the icing was ferocious within, in seemed,
the top 10 ft of the cloud (it was probably more like 100 to 500 but
who knows – it was 20 years ago and I wasn't taking notes at the
time). I always assumed that it was the sun heating the vapor,
droplets, whatever, and forcing them to a higher altitude so they were
a very nearly at their super cooled limit. The dividing line between
ferocious and minimal icing conditions was sharp and very pronounced
during the decent which suggested to me, that sun heating (energy
transfer, if you prefer) was the cause or at least a significant
contributing factor.

In your description of the weather it sounds as though the tops were
increasing in altitude. That suggests lifting agents, e.g. a front or
convective activity, were present. With air movement of that variety it
isn't likely that IR radiation absorption would be able to generate a
stratified effect like you describe. It's more likely that the moisture
near the top was the coldest from convective cooling and was therefore able
to generate the most ice. As you descended you probably encountered
increasing temps, resulting in reduced icing.

Just an educated guess.

JimC

"john cop" wrote in message
om...
Thank you. Makes sense.

In my little experience, the icing was ferocious within, in seemed,
the top 10 ft of the cloud (it was probably more like 100 to 500 but
who knows - it was 20 years ago and I wasn't taking notes at the
time). I always assumed that it was the sun heating the vapor,
droplets, whatever, and forcing them to a higher altitude so they were
a very nearly at their super cooled limit. The dividing line between
ferocious and minimal icing conditions was sharp and very pronounced
during the decent which suggested to me, that sun heating (energy
transfer, if you prefer) was the cause or at least a significant
contributing factor.

I don't have "little experience" flying in icing conditions...I have a lot
of experience flying pistons, turboprops, and jets in an area of the country
so prone to icing (on the west slopes of the Cascades) that the Concorde was
sent out here for icing certification...I flew media folks to Grant County
airport for the occasion.

A good source of information would be Dr. Marcia Politovich at the National
Center for Atmospheric Research in Boulder, Colorado ).
She is known in the aviation meteorology community as the Ice Queen, and has
lots of experience flying in icing research airplanes....but then again you
are not impressed by credentials.

Bob Gardner

"john cop" wrote in message
om...
Thank you. Makes sense.

In my little experience, the icing was ferocious within, in seemed,
the top 10 ft of the cloud (it was probably more like 100 to 500 but
who knows - it was 20 years ago and I wasn't taking notes at the
time). I always assumed that it was the sun heating the vapor,
droplets, whatever, and forcing them to a higher altitude so they were
a very nearly at their super cooled limit. The dividing line between
ferocious and minimal icing conditions was sharp and very pronounced
during the decent which suggested to me, that sun heating (energy
transfer, if you prefer) was the cause or at least a significant
contributing factor.

john cop wrote:
Thank you. Makes sense.

In my little experience, the icing was ferocious within, in seemed,
the top 10 ft of the cloud (it was probably more like 100 to 500 but
who knows – it was 20 years ago and I wasn't taking notes at the
time). I always assumed that it was the sun heating the vapor,
droplets, whatever, and forcing them to a higher altitude so they were
a very nearly at their super cooled limit. The dividing line between
ferocious and minimal icing conditions was sharp and very pronounced
during the decent which suggested to me, that sun heating (energy
transfer, if you prefer) was the cause or at least a significant
contributing factor.

The reason that the top portion of a cloud may produce the most icing...
is that the cloud's formation process has resulted in the most liquid
water near the top.

The formation of most clouds is the result of lift, and as air lifts it
cools at a very substantial rate. When the dewpoint is reached, the
condensation occurs. As the air lifts more, the air becomes colder and
has less capability to support water vapour... hence more
condensation. If the air near the top of the cloud was lifted the
furthest, then that is the air where the most liquid has been condensed.

The fact that the sun may heat the top of the cloud a little, actually
works against icing. By raising the temperature slightly, the air can
support more vapour, and some of the liquid will evaporate.



--
God grant me the serenity to accept the things I cannot change, the
courage to change the things I can, and the wisdom to know the difference.
--- Serenity Prayer

"Icebound" wrote in message
ble.rogers.com...

snip
The fact that the sun may heat the top of the cloud a little, actually
works against icing. By raising the temperature slightly, the air can
support more vapour, and some of the liquid will evaporate.

Liquid evaporating making cold.

A cloud can absorb energy without gaining temperature.