[A-AS06] 成層圏・対流圏過程とその気候への影響

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

*劉 光宇¹、廣岡 俊彦²、江口 菜穂³、Krüger Kirstin⁴ (1.九州大学大学院理学府地球惑星科学専攻、2.九州大学大学院理学研究院地球惑星科学部門、3.九州大学応用力学研究所付属大気海洋環境研究センター、4.Department of Geosciences, University of Oslo)

キーワード：成層圏突然昇温

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.