Response of the Migrating Solar Semidiurnal Tide to Arctic and Antarctic Stratospheric Polar Vortices: A Comprehensive Study

In this study, we use the Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (SD-WACCM-X) to investigate how the migrating solar semidiurnal tide (SW2) in the mesosphere and lower thermosphere (MLT) responds to the strength of Arctic and Antarctic Stratospheric Polar Vortices (SPVs). SW2 shows a substantial response to both SPVs, though the Antarctic influence is weaker. During boreal winter, 50% of SW2 variability is linked to Arctic SPV strength, while 34% during austral spring is associated with Antarctic SPV. Classical tidal theory Hough modes (HMs) of SW2 point to a clear relationship between the HMs and Arctic SPV with the most significant change occurring in the first antisymmetric (2,3) HM. However, only the second symmetric (2,4) HM responds significantly to the Antarctic SPV. These distinctive differences in HMs arise from dynamic changes in the stratosphere and MLT. Stratospheric ozone contributes only 6%–10% to the (2,2) HM during weak state of Arctic SPV and shows no significant influence under Antarctic SPV variability. As such, HM variabilities are primarily caused by changes in background neutral winds during weak and strong Arctic and Antarctic SPVs rather than changes in stratospheric ozone heating. In addition, the zonal momentum budget of each HM of SW2 is analyzed. The classical term (Coriolis + pressure gradient forcing) exhibits the largest variations with the strength of the Arctic and Antarctic SPVs, followed by the advection term.