Westward propagating quasi-10-day wave activity during 2012 – 2016 in the southern high-latitude MLT region using meteor radar observations and SD-WACCM simulations

Using meteor radar observations and specified dynamics of the Whole Atmosphere Community Climate Model (SD-WACCM) simulations, we study about the westward-propagating quasi-10-day wave (Q10DW) in the mesosphere and lower thermosphere (MLT) in the southern hemisphere (SH) high-latitude region. We apply the phase difference technique to zonal winds measured by two meteor radars (Davis; 68.6˚S, 77.9˚E and King Sejong Station; 62.2˚S, 58.8˚W), extracting westward-propagating Q10DW with zonal wavenumber 1 (W1). The amplitude of Q10DW-W1 was often active around equinoxes in some years and during winter in another years. We carried out two experiments that utilize the SD-WACCM with nudging of the MEERA-2 data from the surface up to ~60 km (EXP60) and ~75 km (EXP75) to explain the possible source of the wave. The seasonal variation of Q10DW-W1 from EXP75 is in better agreement with the meteor radar observations than EXP60. The simulation results represent the Eliassen-Palm flux divergence (EPD) in the SH high-latitude upper mesospheric jet enhanced the Q10DW. In addition, spurious Q10DWs appeared more in the EXP60 than in the EXP75 during the summer. Because the gravity wave drag (GWD) can induce the baroclinic/barotropic instability that can be attributed to the EPD, we analyzed the GWD in the SH summer. The results showed that eastward GWD in EXP60 was weaker than in EXP75, inducing enhancement of westward mesospheric jet in EXP60 in the SH high-latitude region and more baroclinic/barotropic instability. These results suggest that GW parameterization should be improved because unrealistic GW parameterization can generate more instability in the SH high-latitude mesopause region, which leads to discrepancy from observations.