On the Importance of Interactive Ozone Chemistry in Earth-System Models for Studying Mesophere-Lower Thermosphere Tidal Changes during Sudden Stratospheric Warmings

We use the CESM2-Whole Atmosphere Community Climate Model, to study the importance of ozone in the vertical coupling between lower and upper atmosphere during sudden stratospheric warmings (SSWs). During SSWs, the build up of stratospheric ozone concentrations at tropical latitudes and its increased asymmetrical distribution carries the potential to affect the generation of migrating and nonmigrating semidiurnal solar tides. Much of the upper atmospheric variability associated with SSWs is known to be driven by large changes in the vertically propagating semidiurnal migrating (SW2) and nonmigrating (SW1 and SW3) solar tides. In this study, we investigate the effect of stratospheric ozone variability during SSWs on these solar tides. For this purpose, a case study of the 2009 SSW event is carried out using the WACCM with two distinct simulation setups. In the first setup, the ozone concentrations are interactively calculated in the model and resemble the ozone observations during the 2009 SSW event, while in the second setup, the ozone concentrations are specified using zonal mean values. We constrain both of the simulations to the Modern-Era Retrospective Analysis for Research and Applications-2 reanalysis so that the background atmosphere through which the solar tides propagate are almost identical in each case. Following the onset of the SSW, we find that in the vicinity of the peak enhancements of SW1, SW2, and SW3 in the mesosphere-lower thermosphere (MLT), the amplitudes of these semidiurnal solar tides are approximately about 15–50% larger for the simulation with interactive ozone as compared with the one with prescribed ozone, indicating that the stratospheric ozone variability plays an important role in driving semidiurnal solar tidal changes during SSWs.