[A-AS06] Stratosphere-troposphere Processes And their Role in Climate

[AAS06-08] Dynamical Features of Antarctic Sudden Stratospheric Warming in 2019

*Guangyu Liu¹, Toshihiko Hirooka², Nawo Eguchi³, Kirstin Krüger⁴ (1.Department of Earth and Planetary Sciences, Kyushu University, 2.Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University, 3.Research Institute for Applied Mechanics, Kyushu University, 4.Department of Geosciences, University of Oslo)

Keywords:sudden stratospheric warming

The sudden stratospheric warming (SSW) is a spectacular event first discovered by Scherhag (1952). During the SSW event, a rapid deceleration or reversed westerly polar vortex along with abrupt increasing temperatures by tens of Kelvins occurs in a few days. The theoretical studies of mechanism of the SSW has been noted that enhanced quasi-stationary planetary waves propagate from the troposphere bring about the SSW (Matsuno 1971; Andrew et al., 1987). The SSW events are commonly observed in Northern Hemisphere (NH) but rarely occur in the Southern Hemisphere (SH) due to its geographical condition, topography and land-sea temperature contrast.

The present study analyzed the unusual SSW event in September 2019 (hereafter SSW2019) in the SH with comparing to the only major SSW occurred in 2002 (hereafter SSW2002) by using the Japanese 55-year Reanalysis (JRA-55) data. The reversal temperature gradient between the south pole and 60S, decelerated westerly winds in 60S and 10 hPa were observed. It is found that the quasi-stationary wave driving with zonal wavenumber 1 play an important role in the occurrence of SSW2019, which brought a large disturbance on the polar vortex and decelerate the polar nigh jet. However, because the reversal of westerly winds to easterly winds have not been observed at 60S, 10 hPa, the SSW2019 was classified as a minor warming event.