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.