Dynamics, radiation, and photochemistry in the mesosphere: implications for the formation of noctilucent clouds

This paper attempts to illustrate by means of model calculations how various dynamical and photochemical processes interact to produce the unique environment that makes possible the existence of noctilucent clouds. In particular, it focuses on how thermal relaxation influences the altitude and strength of gravity wave breaking and on the effects of such wave breaking on the circulation, temperature distribution, and transport of water vapor near the summer mesopause. It is also shown that, if present understanding of hydrogen chemistry in the mesosphere is even approximately correct, variations in Lyman α radiation should have a significant effect on water vapor abundances near the summer mesopause and, therefore, on the occurrence of noctilucent clouds. -from Author