IT Predictability During SSWs with CESM2[WACCM6] and TIE-GCM

The impacts of sudden stratospheric warming (SSW) events in the mesosphere and lower thermosphere are known to be predictable as many 20 days prior to the onset of such an event, and SSWs are also known to impact, for example, global thermospheric circulation and low latitude ion drifts. Therefore, we investigate the predictability of the ionosphere-thermosphere (IT) region during sudden stratospheric warmings (SSWs) by using subseasonal hindcasts in the Community Earth System Model, version 2 with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM2[WACCM6]) to force the lower boundary of the NCAR/HAO Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM). By analyzing 18 major SSW events occurring between 1999 and 2023, we find that hindcasts initialized ~15-20 days prior to the onset of SSW events are able to predict (1) the timing of the SSW in the Mesosphere-Lower-Thermosphere (MLT), and (2) corresponding anomalies in the F-region ion drifts temperatures, and densities, as well as in thermospheric composition tracked by the ratio of atomic oxygen to molecular nitrogen (O/N2). This study demonstrates that improved space weather forecasting is achieved by using whole atmosphere models that can predict the MLT variability that drives ionosphere-thermosphere variability during SSWs.