Local Thermodynamic Equilibria | partial LTE | non-LTE

The study of radiation is part quantum mechanics, optics and thermodynamics. If one wishes to technically understand how climate models handle radiation, it is best to begin with the study of local thermodynamic equilibria (LTEs). However, it should be acknowledged that this is only an approximation - although decidedly better than that which is assumed by the "simple model." Most of what we will be considering in terms of technical radiation theory consists of conditions which hold in local thermodynamic equilibria. However, climatology has already moved beyond local thermodynamic equilibria and is beginning to model radiation in terms of partial-LTEs where the equilibrium conditions are assumed to apply only for some gases at for certain ranges of temperatures and pressures over specific bands of their spectra. Finally, there are non-LTEs, that is, non-local thermodynamic equilibria.