Latitudinal and longitudinal behavior of the mesospheric OH nightglow layer as observed by the Improved Stratospheric and Mesospheric Sounder on UARS

The mesospheric nightglow from the hydroxyl (OH) radical has been character ized using measurements taken by the Improved Stratospheric and Mesospheric Sounder (ISAMS) instrument on the UARS satellite. In this paper, the varia tions with latitude of the emission integrated vertically over the OH layer , for both solstice and equinox conditions, are analyzed and compared to ot her measurements and with model predictions. A semiannual variation with a minimum at solstice is found at low latitudes. An annual variation is found at high latitudes with a springtime minimum, which appears earlier than pr edicted by the models. Zonal maps of the OH emission show longitudinal stru ctures with a timescale of days that suggest the effect of planetary waves on the emission process.