Extracting Semidiurnal Non-Migrating Tides from Simultaneous Observations of Temperature and Composition from the GOLD Mission

Non-migrating tides control the longitudinal dependence of the tidal response of the mesosphere/lower thermosphere (MLT). There are few observations of semidiurnal tides between 120 and 200 km altitude, a region where both upward propagating and in situ semidiurnal tides are expected to be present. From geostationary orbit, the Global-scale Observations of the Limb and Disk (GOLD) Mission has routinely imaged the disk temperature (~150 km) and the column density ratio of atomic oxygen to molecular nitrogen ratio (O/N2) over a ~140° longitude sector of the Earth on the dayside. A complete frequency-wavenumber decomposition is not possible owing to the incomplete local time and longitudinal coverage. Here, we use simultaneous observations of temperature and O/N2 to diagnose semidiurnal non-migrating tides by adapting an approach that deduces diurnal non-migrating tides. We focus on solstice conditions at summer mid-latitudes because of the optimal 12-hour local time sums afforded by those times and regions. These results are the first observations of semidiurnal non-migrating tides in the MLT from a geostationary observational platform.