On the latitudinal variations of the non-periodic response of minor species induced by a dissipative gravity-wave packet in the MLT region

A spectral full-wave model and a two dimensional (2-D), time dependent, fully nonlinear chemistry model were used to investigate the latitudinal variations of the wave effects on the minor species in the OH chemistry in the mesosphere/lower thermosphere region. A dissipative gravity-wave packet is launched at three different latitudes propagating upward through the OH nightglow emission layer in the northern hemisphere. In addition to causing the minor species densities to fluctuate, the wave packet also causes non-periodic secular variations of the minor species densities as a consequence of violation of the non-acceleration conditions due to wave transience and dissipation. The associated fluxes of minor species are downward, and consequently minor species densities typically decrease at higher altitudes and increase at lower altitudes. The downward flux and subsequent chemical recombination of atomic oxygen is particularly important and can itself cause large secular variations of other less abundant minor species. Our studies indicate that the wave-induced non-periodic, secular variations are largest at high latitudes, second largest at low latitudes, and smallest at mid-latitudes.