On the abnormally strong westward phase of the mesospheric semiannual oscillation at low latitudes during March equinox 2023

This event was the strongest of at least the last decade (2014-2023). The westward winds reached -80 m/s at 82 km of altitude in late March, and decreased with increasing altitude and latitude.

A considerable increase in the diurnal tide amplitude was also observed. The Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension constrained to meteorological reanalysis up to similar to 50 km does not capture the observed low-latitude behavior. Additionally, these strong mesospheric winds developed during the westerly phase of the Quasi-Biennial Oscillation, in accordance with the filtering mechanism of gravity waves in the stratosphere proposed in previous works.