Deducing Non‐Migrating Diurnal Tides in the Middle Thermosphere With GOLD Observations of the Earth's far Ultraviolet Dayglow From Geostationary Orbit
Christopher Scott Krier, S. England, K. Greer, J. S. Evans, A. G. Burns, R. Eastes
Abstract
Abstract The global‐scale observations of the limb and disk (GOLD) Mission images middle thermosphere temperature and the vertical column density ratio of oxygen to molecular nitrogen ( O/N 2 ) using its far ultraviolet imaging spectrographs in geostationary orbit. Since GOLD only measures these quantities during daylight, and only over the ∼140° of longitude visible from geostationary orbit, previously developed tidal analysis techniques cannot be applied to the GOLD data set. This paper presents a novel approach that deduces two specified non‐migrating diurnal tides using simultaneous measurements of temperature and O/N 2 . DE3 (diurnal eastward propagating wave 3) and DE2 (diurnal eastward propagating wave 2) during October 2018 and January 2020 are the focus of this paper. Sensitivity analyses using TIE‐GCM simulations reveal that our approach reliably retrieves the true phases, whereas a combination of residual contributions from secondary tides, the restriction in longitude, and random uncertainty can lead to ∼50% error in the retrieved amplitudes. Application of our approach to GOLD data during these time periods provides the first observations of non‐migrating diurnal tides in measurements taken from geostationary orbit. We identify discrepancies between GOLD observations and TIE‐GCM modeling. Retrieved tidal amplitudes from GOLD observations exceed their respective TIE‐GCM amplitudes by a factor of two in some cases.