Statistical analysis of neutral winds in the MLT using 14 years (2007-2020) of meteor radar data at King Sejong Station

Abstract

As the mesosphere and lower thermosphere (MLT) region is an important layer connecting the lower atmosphere and the space, investigation of neutral winds in the MLT region is essential to understand a coupling process between them. The meteor radar at King Sejong Station, Antarctica (KSS; 62.22°S, 58.78°W) has been continuously observing neutral winds in the MLT region regardless of weather conditions since March 2007. In this study, statistical analysis of the neutral winds in the MLT is conducted using 14-year (2007-2020) meteor radar observations over KSS. In a zonal wind, an annual variation with the strongest easterlies in summer is evident below 90 km, while a semiannual variation with two peaks in both solstices can be found above 90 km. The meridional wind is smaller in magnitude than the zonal wind and its temporal variation extends from days to annual timescales. Poleward winds dominates in winter and summer, while equatorward winds appear in spring and autumn. Statistically significant decreasing trends in the observed zonal wind exist in autumn, while increasing trends are found in winter. In contrast, there are no significant linear trends in the meridional wind. Spectral analysis of the observed horizontal winds is performed to investigate the characteristics of tides and planetary waves. Strong semidiurnal tidal signals are found from autumn to spring with a maximum amplitude in May, while diurnal tidal signals are evident in summer. The activities of 2-day waves are strong in both summer and winter, whereas 4-day wave signals are mainly observed in winter. Further investigation of the possible cause of the long-term variations in the neutral winds in the polar MLT will be conducted.