Seasonal Variability of the DE3 and DE2 Non‐Migrating Tides in Middle Thermospheric Temperature and Composition During October 2018–August 2021 as Revealed by GOLD

Abstract A subset of non‐migrating tides, including the diurnal eastward propagating tides with zonal wavenumbers 3 and 2, respectively, referred to as DE3 and DE2, are upward propagating waves that have been studied as phenomena that couple the lower atmosphere with the thermosphere. While the climatology of non‐migrating tides in the mesosphere/lower thermosphere and the upper thermosphere has been characterized observationally, very little is known about their behavior in the so‐called “thermospheric gap” between 110 and 200 km where observations are sparse. This paper reports upon the observed seasonal variability of DE3 and DE2 between October 2018 and August 2021 at low latitudes in temperature, corresponding to about 160 km, and the thermospheric column density ratio of atomic oxygen to molecular nitrogen (O/N 2 ). Our observational analysis employs satellite data from NASA's GOLD instrument in geostationary orbit and a tidal extraction approach that retrieves DE3 and DE2 from differences with local time assuming no contributions from other tides. The tidal amplitudes observed using GOLD are compared to a physics‐based model, an empirical tidal model, and an independent contemporaneous data set. We find that the seasonal variability of the GOLD tides are poorly correlated with that found in the other data sets. DE3 variations in GOLD O/N 2 are positively correlated with an in situ generated DW5 simulated by a physics‐based model. These results provide indirect observational evidence of in situ generated tides in the thermosphere, which contribute to the diurnal non‐migrating signal in GOLD observations at low latitudes in addition to the upward propagating DE3 and DE2.