Upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events

In addition to the radar wind data, the analysis has been applied to simulations from Whole Atmosphere Community Climate Model Extended version and the thermosphere-ionosphere-mesosphere electrodynamics general circulation model. Our results indicate that the semidiurnal lunar tide (M₂) enhances in northern hemispheric winter months, over both middle and high latitudes. The time and magnitude of M₂ are highly correlated with the time and associated zonal wind of PVW.

At middle/high latitudes, M₂ in the upper mesosphere occurs after/before the PVW. At both latitudes, the maximum amplitude of M₂ is directly proportional to the strength of PVW westward wind. We have found that M₂ amplitudes could be comparable to semidiurnal solar tide amplitudes, particularly around PVW and equinoxes.

Besides these general results, we have also found peculiarities in some events, particularly at high latitudes. These peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions. For example, during SSW 2009, we found that M₂ enhances many days before PVW which is not in agreement with most of our results.