Comment on “Middle atmosphere heating by exothermic chemical reactions involving odd‐hydrogen species”

In a recent letter Mlynczak and Solomon [1991] (hereafter M&S) have assessed the atmospheric heating rates associated with the exothermic odd hydrogen reactions 0+0H -• H+0• H+O2+M --+ H0•+M O+HO2 '--> OH+O2 H+O• --} OH+O• These authors (M&S) find that the reactions are a significant source of heat in the middle atmosphere and that the H+O3 reaction makes the single most important contribution.As M&S explained, some of the energy released in the H+O3 reaction is radiated from the atmosphere in the OH Meinel band airglow emission and they have used the Meinel band excitation models of McDade and Llewellyn [1987] and Lopez-Moreno et al. [1987] to calculate the fraction of the exothermicity that is locally degraded into heat.In their letter M&S report that the peak nighttime heating rams calculated for the collisional cascade and sudden death models of McDade and Llewellyn [1987] are much smaller than those obtained Planet.