Short-term to Inter-annual Variability of the Non-migrating Tide DE3 from MIGHTI, SABER, and TIDI: Potential Tropospheric Sources and Ionospheric Impacts

A growing body of research indicates that upward propagating waves of terrestrial origin play an important role in shaping the dynamical structure of the mesosphere, thermosphere, and ionosphere on daily to interannual timescales. Important progress has been made in understanding their role as coupling agents between the terrestrial weather and space weather on monthly to interannual timescales. However, due to the limited local time sampling by space-based observations and spatial gaps in the observations by ground-based chain of instruments, their short-term (<30 day) variability has not been resolved. This study addresses the short-term variability of the DE3 nonmigrating tide (diurnal, eastward-propagating, zonal wave number 3), which is one of the consequential upward propagating tides of lower atmospheric origin, and investigates its connection with the ionosphere. First, we demonstrate and validate a short-term estimation technique at the equator utilizing physics-based model simulations and then implement the technique on SABER, MIGHTI, and TIDI measurements in the MLT region. We find that daily tidal DE3 estimates from SABER, MIGHTI, and TIDI at the equator are in mutual agreement, with correlation coefficients ranging from 0.76 to 0.85. The daily tidal variability in TIDI and SABER amplitudes is typically ∼7 m/s and ∼3 K, respectively. We also find that daily MLT variations and F-region ionospheric DE3 from COSMIC-2 Global Ionospheric Specification (GIS) show a moderate correlation of 0.44, suggesting that not all ionospheric variability can be attributed to the E-region dynamo; however, increasing correlation with increasing time-scale suggests that lower atmospheric variability have pronounced impact on the ionosphere on intra-seasonal scales. We find that the MLT and the F-region ionosphere exhibit strong coherent intra-seasonal oscillations (residual amplitudes up to 50-60%); their coherency with the MJO in 2020 suggests a possible modulation of the upward propagating DE3 tide related to this major tropical tropospheric weather pattern. In addition, we find stratospheric QBO signatures in the MLT DE3 on inter-annual scales. This study offers fresh observational insights into the pivotal role of tropospheric weather in shaping variability in the coupled thermosphere-ionosphere system.