Mesosphere and lower thermosphere winds and tidal variations during the 2019 Antarctic Sudden Stratospheric Warming

Realistic modeling of the winds and dynamical variations in the mesosphere and lower thermosphere (MLT) at Southern Hemisphere (SH) mid-to-high latitudes near 60oS where dramatic motions occur has been a challenge. This work presents an evaluation of the MLT zonal and meridional winds from ∼80-98 km altitude produced by the high-altitude version of the Navy Global Environmental Model (NAVGEM-HA) numerical weather prediction system during the Antarctic Sudden Stratospheric Warming (SSW) in September 2019. These results are compared with the coincident measurements by five meteor radars at Tierra del Fuego (TDF; 53.7oS, 67.7oW), King Edward Point (KEP; 54.3oS, 36.5oW), King Sejong Station (KSS; 62.2oS, 58.8oW), Rothera (ROT; 67.5oS, 68.0oW), and Davis (DAV; 68.6oS, 78.0oE) across SH mid-to-high latitudes. We find that the day-to-day variations in NAVGEM-HA winds related to tidal motions are overall consistent with variations in the radar winds, and the daily mean winds have a correlation of 0.7-0.9 between them. 3-hourly NAVGEM-HA winds have a correlation of ∼0.5 and mean difference <10 m/s to the radar observations at most stations, and the Root Mean Square (RMS) error ranges from ∼25 to 35 m/s. Above 90 km altitude, the correlation coefficient decreases, and the difference and RMS error increase, indicating an upper limit to the validity of the NAVGEM-HA results. Both the analyzed and observed winds reveal an enhancement in diurnal and semidiurnal tidal amplitude during this SH SSW. NAVGEM-HA shows some evidence that nonmigrating tidal enhancements are produced through the interaction of migrating tides with planetary waves.

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