Variability in MLT dynamics and species concentrations as observed by WINDII

Abstract

Airglow variability is a topic that has been studied for decades but an understanding of the role of the dynamical influence underlying this variability has only been achieved recently. The UARS dynamics instruments, HRDI (High Resolution Doppler Imager) and WINDII (WIND Imaging Interferometer) have been instrumental in providing this understanding, because they measure both winds and emission rates, and so are able to determine the coupling between the two. But ground-based observations are also an essential ingredient to this understanding, which has grown through intercomparisons between dataset and models through workshops such as DYSMER. This presentation begins by describing the influence of the diurnal tide on oxygen and hydroxyl airglow emission rates, including the seasonal variation. This is followed by a description of two planetary scale disturbance phenomena, the springtime transition, and a stratospheric warming. Auroral influences are also considered. While these investigations cover a wide range of mechanisms there is an underlying thread which is that it is these large scale dynamical processes that are responsible for determining the distribution of the airglow patterns detected, and thus the distribution of concentration of atomic oxygen.