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

In this study, we use the Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (SD-WACCM-X) to study the variability of the migrating solar semidiurnal tide (SW2) in the mesosphere and lower thermosphere (MLT) in response to the strength of Arctic and Antarctic Stratospheric Polar Vortices (SPV). Our analyses reveal that SW2 shows a substantial response to both hemisphere SPVs, but with a weaker sensitivity to the Antarctic SPV. Classical tidal theory Hough mode (HM) analysis of SW2 points to a clear relationship between the first two symmetric and antisymmetric HMs of SW2 and Arctic SPV with the most significant change in the first asymmetric (2,3) HM. However, only the second symmetric (2,4) HM shows a variability in response to Antarctic SPV. These distinctive differences in HM variations are due to dynamic changes in the stratosphere and MLT. We find a small role of stratospheric ozone in the SW2 variations during different states of Arctic SPV. However, in the case of Antarctic SPV, we do not find a significant impact of stratospheric ozone on the SW2 variabilities. As such, HM variabilities are mostly caused by changes in the background neutral winds during weak and strong Arctic and Antarctic SPVs and not due to tidal heating variations. In addition, the zonal momentum budget of each Hough mode of SW2 is analyzed. The classical term (Coriolis plus pressure gradient forcing) exhibits the largest variations with the strength of the Arctic and Antarctic SPVs, followed by the advection term.