2011-09-08 22:38:00Help on Planck Damping


I'm trying to read the following paper:

Effect of the temperature dependence of gas absorption in climate feedback (Yi Huang and V. Ramaswamy)

It has references to the "Planck effect" and "Planck damping" which, interestingly, are terms that only show up in Google in papers written by Huang.

My guess from my limited understanding and the context of the paper is that Planck's Law causes a shift in the frequencies being absorbed and emitted, and in so doing changes the absorption characteristics between layers.  That is, that when one layer gets warmer, it emits in a slightly different frequency and so the radiation may pass through other, cooler layers without being absorbed.

This doesn't entirely make sense to me, given the quantum nature of things, except through Doppler broadening, which I wouldn't think would affect things to too great a degree.

But I don't know, and I can't find a good place to read up on it without having to go through half of a PhD worth of background physics texts.  Unfortunately, I'm swamped with "paying" work, so I just don't have the time to give this the attention that I'd like.


Can anyone briefly explain what he means by the Planck effect, and the point of the paper as a whole?

At the same time... is this paper accepted in the literature, and what is it's overall impact?

2011-09-08 23:48:45


Never heard about a "Planck effect" either. From the introduction:

Atmospheric temperature directly influences the thermal emission according to Planck’s Law [Goody and Yung, 1989]. In addition, the absorptivities of the various gaseous components in the atmosphere, being temperature-dependent, influence the transmission and emission of radiation energy following Kirchhoff’s Law.

These are the two terms of the temperature feedback. The former is the known increase in emission, given by the Plank law, due to an increase in temperature. In a simple grey atmosphere model it woud be the εσT^4 term. This is what they call the "Plank effect".

They compare the Plank effect to the "absorptivity effect" (split into several components) and show that the former tend to dominate due to a cancellation effect of the components of the latter.
No mention of a frequency shift of the absorption lines, which indeed would be new to me.

2011-09-09 00:57:39


Okay, I was reading more into it than was there.  I assumed there was something else being referenced that I didn't know.

I should have just jumped to the conclusion, which states things even more succinctly.  Thank you.