A whole-atmospheric perspective on connections between intra-seasonal variations in the troposphere and thermosphere

Mounting evidence has 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. Much of this coupling is carried by waves that are excited by deep convection in the tropical troposphere and that propagate vertically into the thermosphere. While observations have shown significant intra-seasonal variability in the upper mesospheric mean winds, relatively little is known about this variability at satellite altitudes ( 250-400 km). Using satellite observations (e.g., CHAMP, GOCE, TIMED/SABER), numerical models (TIME-GCM, WACCM-X 2.0), reanalysis data (e.g., MERRA-2), and Outgoing Longwave Radiation (OLR) data, we present evidence of a prominent and global-scale 90 day oscillation in the thermospheric zonal mean winds and in tropical tropospheric waves (e.g., DE3, UFKW) during 2009-2010 and present evidence of its connection to variability in tropospheric convective activity. We further elucidate the vertical evolution of this 90-day oscillation from the lower to the upper atmosphere and investigate potential connections to the Madden-Julian Oscillation (MJO). This study demonstrates that strong coupling between the troposphere and the thermosphere is occurring on intra-seasonal timescales, raising important questions including implications for the whole atmosphere system.