The effects of gravity waves on distributions of chemically active constituents in the mesopause region

The influence of a monochromatic atmospheric gravity wave of fixed amplitude on the mean vertical distribution of mesospheric minor species is studied using a dynamical-photochemical gravity wave model. The fluctuations of winds, temperature, and species concentrations produced by the wave are calculated by a coupled linear gravity wave model. The effects of the wave on the mean mixing ratio of 19 key chemically active species is derived from a coupled system of continuity equations which accounts for full nonlinear photochemistry in a vertical column. This study focuses on the impact that gravity wave induced nonlinearities in the chemical reaction rates has on the chemical species distribution. The effects of gravity wave induced chemical transport and background diffusion are also calculated. Calculations indicate that the impacts of gravity waves on the vertical distribution (mean concentration) of atmospheric minor constituents are largest in the mesopause region, especially during nighttime. A comparison of the three effects indicates that for short lifetime chemical species such as O₃ and OH, the tendency due to chemical reaction perturbations induced by gravity waves is much greater than that due to transport and diffusion. The altitude range over which these nonlinearities is important is narrowly confined to the chemically active region near the mesopause.