This paper considers a nature of some sources of infra-red radiation in the Earth's atmosphere as a result of infra-red characteristic radiation (IRCR) of first order phase transitions - condensation and crystallization of water. Experimental and theoretical evidences of the IRCR existence are discussed. The theory of the phenomenon is based on the claim that the particle's (atom, molecule, or cluster) transition from a higher energetic level (vapor or liquid) to a lower one (liquid or crystal) produces emission of one or few photons. The energy of these photons is connected by definite way with the latent energy of the phase transition. The effect under investigation must play a very important role in atmospheric phenomena: it is one of the sources of Earth's cooling; formation of hailstorm clouds in the atmosphere is accompanied by the intensive IRCR that could be detected for process characterization and meteorological warnings. The effect can be used for atmospheric heat accumulation. The IRCR might explain the red color and infrared emission of Jupiter.
first order phase transitions of water: condensation and crystallization; infra-red radiation; atmospheric phenomena; formation of hail; Jupiter; infra-red laser