Quasi-stationary Planetary Waves during the 2018–2019 Elevated Stratopause Event

The winter of 2018－2019 at high latitudes in the Northern Hemisphere was characterized by an Elevated Stratospheric (ES) event, and the role played by various atmospheric fluctuations in this event is not fully understood. Using satellite and reanalysis data, the changes in the stratopause and background atmosphere before and after this ES event were demonstrated, providing insights into the activity of quasi-stationary planetary waves in the stratosphere and lower mesosphere. The results show that the quasi-stationary planetary waves with a zonal wave number of 1 began to intensify in early December and reached a maximum in mid-December. A strong westerly wave forcing on the background atmosphere is shown throughout December, the descending and warming phase of the original stratopause. After the ES, the wave activity weakened and the tug on the background atmosphere was weak, and may not have been involved in the subsequent phases of the ES event. The quasi-stationary planet with a zonal wave number of 2 has a weak activity before the ES, and starts to strengthen in mid-January, and shows westward wave forcing on the background atmosphere from the middle of January to the end of February, during the stage of the formation of the upper stratopause and the subsequent stages of the descent and warming, and the decrease of the center of the forcing with the altitude coincides with the decrease of the upper stratopause, which suggests that the wave mainly plays a role in this stage.