A simple model of diurnal variations in the mesospheric oxygen nightglow



Local time variations in the OH, and O2(b¹Σ g+) and O(¹S) nightglow have recently been reported in observations by the Wind Imaging Interferometer (WINDII) and the High Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) and attributed to dynamical effects associated with the migrating diurnal tide. A simple model involving vertical advection, a background atmosphere from MSIS, and a latitudinal variation in amplitude given by the (1,1) Hough mode is developed and found to duplicate many of the features of the satellite observations. The model demonstrates that vertical advection is the prime process causing these airglow variations. The observed variability in the relative phases and intensities between these nightglow signatures are most likely due to variations in the phase, amplitude and/or vertical wavelength of the tide, and/or the background oxygen mixing ratio. Given the ubiquitous nature of the tidal influence in the mesopause region any attempt to determine background atmospheric parameters from nightglow signatures must take the dynamical effects of the diurnal tide into account.