First Observational Evidence for the Role of Polar Vortex Strength in Modulating the Activity of Planetary Waves in the MLT Region

Based on the meteor winds measured at Mohe (MH; 53.5 degrees N, 122.3 degrees E) and the reanalysis data, we investigate the variations of planetary waves in the mesosphere and lower thermosphere (MLT) region during the 2019/2020 Arctic winter. Four stratospheric polar warmings, including two sudden stratospheric warmings (SSWs), are observed from November 2019 to March 2020. Quasi-10-day waves (Q10DWs) are found to be enhanced following three of these warmings in the zonal winds in the MLT region over MH, but unusually weak after the SSW in February 2020. The trigger mechanisms of the enhanced Q10DWs are investigated and the reason for the unusually weak Q10DWs in February is revealed. Upward propagations and in situ generations of Q10DWs are both limited during the February SSW. Our analysis indicates that Q10DWs in the MLT region in February 2020 are largely inhibited by the extremely strong polar vortex and a lack of mesospheric instability.

Automated summary

This article investigates the variations of planetary waves in the mesosphere and lower thermosphere (MLT) region during the 2019/2020 Arctic winter. The study finds that quasi-10-day waves (Q10DWs) are enhanced following sudden stratospheric warmings (SSWs), but become unusually weak after the SSW in February 2020. The analysis reveals that the weak Q10DWs in February are largely inhibited by the extremely strong polar vortex and a lack of mesospheric instability.