Coupling of Long‐Term Trends of Zonal Winds Between the Mesopause and Stratosphere in Southern Winter

We examine the relationships between the observed long‐term trends of the zonal wind in the mesopause regions at King Sejong Station (KSS), Antarctica, and wind trends in the Southern Hemisphere (SH) middle atmosphere using the 15‐year data set from KSS meteor radar, Aura MLS and MERRA‐2. During July, significant positive trends of zonal winds appear above z = 90 km and near the stratopause over the KSS, while negative trends exist between the two layers. In the SH winter, the observed mesopause winds correlate positively (negatively) with stratospheric (mesospheric) winds in the polar region, while they exhibit opposite correlations with the low‐latitude winds. The positive mesopause trends of zonal winds near KSS are connected, through the thermal wind relationship, to cooling (warming) trends induced by the upward (downward) trends of residual circulation over the high‐latitude mesosphere and low‐latitude stratosphere (high‐latitude stratosphere), which shows vertical coupling throughout the SH winter middle atmosphere. Plain Language Summary Based on 15‐year (2007–2021) observations of horizontal winds obtained at mesopause altitudes of 80–100 km by a meteor radar at King Sejong Station (KSS; 62.22°S, 58.78°W), Antarctica, we find long‐term trends of eastward winds above 90 km in July. To investigate the relationship between the observed long‐term trends of the mesopause wind over the Southern Hemisphere (SH) polar region and winds in the SH middle atmosphere, we analyze Aura MLS satellite data and MERRA‐2 reanalysis data. In the SH winter, the mesopause zonal winds over polar regions are positively (negatively) correlated with zonal winds in the polar stratosphere (polar mesosphere), while the opposite correlations are found between the polar mesopause and low latitudes. We demonstrate that the trends of temperature induced by adiabatic warming or cooling associated with meridional circulation in the stratosphere and mesosphere are connected to the observed mesopause wind trends in the polar region (KSS), which accounts for the vertical coupling between the mesopause region and stratosphere across the mesosphere. Key Points Trends of zonal winds in the Southern Hemisphere mesopause and stratosphere are investigated using meteor radar and satellite observations Significant correlations are found between the mesopause wind at high latitudes and the winds in the middle atmosphere The observed wind trends in austral winter are coupled vertically between t