Lower Atmospheric Drivers of Upper Atmospheric Day-to-Day Variability Over Alaska in Arctic 2018–2019 Winter

Day-to-day variability in the Arctic winter thermosphere is driven, in part, by weather in the middle and lower atmosphere. The research presented here investigates the link between day-to-day stratospheric conditions, and local I-T variability over Alaska during the 2018–2019 Arctic winter. This work uses 4.3-μm brightness temperature perturbation variances from the Atmospheric Infrared Sounder (AIRS) to quantify GW activity in the stratosphere, temperature perturbations from the High Altitude Mechanistic general Circulation Model (HIAMCM) to infer GW activity in the thermosphere, and Incoherent Scatter Radar electron density measurements for Medium Scale Traveling Ionospheric Disturbances (MSTID) activity in the ionosphere. We find that GW activity in the stratosphere and thermosphere, and MSTID activity in the ionosphere were suppressed during the 2018–2019 sudden stratospheric warming. These MSTID observations are in good agreement with HIAMCM thermospheric GW activity output. MSTID activity over Alaska is linked to stratospheric GW activity over Europe and NE Russia at different times during the season, highlighting the importance of cross-polar GW propagation. MSTID amplitudes over Alaska are also positively correlated with polar vortex strength and stratospheric wind speeds over Alaska at 50 km. These results support the conclusion that the I-T region is strongly coupled to the lower atmosphere through GW interactions with the polar vortex and their subsequent cross-polar propagation. While the importance of lower atmospheric drivers has previously been shown at mid-latitudes, this research emphasizes the importance of the polar vortex and lower atmospheric GW coupling in driving MSTID and thermospheric GW variability at high latitudes.