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 amplitud e on the mean vertical distribution of mesospheric minor species is studied using a dynamical-photochemical gravity wave model. The fluctuations of wi nds, temperature, and species concentrations produced by the wave are calcu lated by a coupled linear gravity wave model. The effects of the wave on th e mean mixing ratio of 19 key chemically active species is derived from a c oupled system of continuity equations which accounts for full nonlinear pho tochemistry in a vertical column. This study focuses on the impact that gra vity 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 indic ate that the impacts of gravity waves on the vertical distribution (mean co ncentration) of atmospheric minor constituents are largest in the mesopause region, especially during nighttime. A comparison of the three effects ind icates that for short lifetime chemical species such as O-3 and OH, the ten dency due to chemical reaction perturbations induced by gravity waves is mu ch greater than that due to transport and diffusion. The altitude range ove r which these nonlinearities is important is narrowly confined to the chemi cally active region near the mesopause.