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In the last decade evidence demonstrated that terrestrial weather greatly impacts the dynamics and mean state of the thermosphere via small-scale gravity waves and global-scale solar tidal propagation and dissipation effects. While observations have shown significant intraseasonal variability in the upper mesospheric mean winds, relatively little is known about this variability at satellite altitudes (similar to 250-400 km). Using cross-track wind measurements from the Challenging Minisatellite Payload and Gravity field and steady-state Ocean Circulation Explorer satellites, winds from a Modern-Era Retrospective Analysis for Research and Applications/Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model simulation, and outgoing longwave radiation data, we demonstrate the existence of a prominent and global-scale 90 day oscillation in the thermospheric zonal mean winds and in the diurnal eastward propagating tide with zonal wave number 3 (DE3) during 2009-2010 and present evidence of its connection to variability in tropospheric convective activity. This study suggests that strong coupling between the troposphere and the thermosphere occurs on intraseasonal timescales.

Plain Language Summary Many of the beneficiaries of space weather forecasts need to predict conditions to accurately calculate satellite ephemeris. In terms of a broader scale, all systems that are affected by the thermosphere greatly benefit from accurate predictions, whether the system is the magnetosphere, the mesosphere, or even large-scale power grids. Ideally, it would be possible to quantitatively predict the global state of the thermosphere a number of days in advance. The ability to accurately predict implies understanding of the physical mechanisms at work in the system. Results from our study suggest that a strong coupling between the lower and upper atmosphere occurs on intraseasonal timescales.