0
$\begingroup$

There are topics on how water vapour absorbs radiation ("How does carbon dioxide or water vapour absorb thermal infra red radiation from the sun?"), but what I am looking for is can water vapour also emits radiation in the following proces?

When water vapourize for example from the ocean, it contains latent heat. When water vapour rises into the atmosphere it can absorb radiation.

Will / can water vapour also emit heat in the form of radiation before it condenses into the liquid form? I know it will transmit radiation in the phase change, but I am only looking in the phase before the phase change.

$\endgroup$
0
$\begingroup$

Yes, it will. In general it can emit radiation at any frequency it absorbs it at, and it will do so. However this emission is essentially random, because the orientation of the molecules is random, so even if molecules don't emit radiation isotropically (ie if they don't emit radiation equally in all directions relative to the orientation of the molecule) the overall pattern is random.

$\endgroup$
  • $\begingroup$ The direction is random even if we neglect scattering. Even if the atoms radiated in some anisotropic pattern, their orientation being random smooths this pattern to be isotropic. $\endgroup$ – Ruslan Jun 29 at 5:53
  • $\begingroup$ @Ruslan: thanks, I've amended my answer. $\endgroup$ – tfb Jun 29 at 8:34
  • $\begingroup$ "Not equally in all directions" is anisotropically, not isotropically. $\endgroup$ – Ruslan Jun 29 at 8:36
  • $\begingroup$ @Ruslan Doh, sorry. Fixed the sense of the sentence to be right. $\endgroup$ – tfb Jun 30 at 10:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.