September 2019 Antarctic Sudden Stratospheric Warming: Quasi‐6‐Day Wave Burst and Ionospheric Effects

Y Yamazaki,M Kozubek,Y Miyoshi,W Ward,T Siddiqui,S Kristoffersen,P Alken,G Kervalishvili,D R Themens,V Matthias,J Laštovička,C Stolle

doi:10.1029/2019gl086577

Abstract

AbstractAn exceptionally strong stationary planetary wave with Zonal Wavenumber 1 led to a sudden stratospheric warming (SSW) in the Southern Hemisphere in September 2019. Ionospheric data from European Space Agency's Swarm satellite constellation mission show prominent 6‐day variations in the dayside low‐latitude region at this time, which can be attributed to forcing from the middle atmosphere by the Rossby normal mode “quasi‐6‐day wave” (Q6DW). Geopotential height measurements by the Microwave Limb Sounder aboard National Aeronautics and Space Administration's Aura satellite reveal a burst of global Q6DW activity in the mesosphere and lower thermosphere during the SSW, which is one of the strongest in the record. The Q6DW is apparently generated in the polar stratosphere at 30–40 km, where the atmosphere is unstable due to strong vertical wind shear connected with planetary wave breaking. These results suggest that an Antarctic SSW can lead to ionospheric variability through wave forcing from the middle atmosphere.

Highlights

A sudden stratospheric warming (SSW) is a large-scale meteorological phenomenon in the winter stratosphere, which involves a rapid rise in the polar temperature by a few tens of kelvins in several days (Andrews et al, 1987; Labitzke & Van Loon, 1999)
The polar temperature at hPa, obtained from the MERRA-2 reanalysis (Gelaro et al, 2017), shows a rapid increase from 207.7 K on 5 September to 258.5 K on September 2019 (ΔT = 50.8 K/week) (Figure 1a). This is the largest increase in the Antarctic polar temperature per week in the entire MERRA-2 data set starting from January 1980
No similar enhancement is found in the amplitude of the stationary planetary waves (PWs) with ZW2

Summary

Introduction

A sudden stratospheric warming (SSW) is a large-scale meteorological phenomenon in the winter stratosphere, which involves a rapid rise in the polar temperature by a few tens of kelvins in several days (Andrews et al, 1987; Labitzke & Van Loon, 1999). PW breaking in the middle atmosphere leads to an acceleration of the zonal mean flow and changes the mean meridional circulation (Matsuno, 1971). Dynamical effects of PW breaking during SSWs are not limited in the stratosphere but are well extended into the mesosphere and lower thermosphere (Chandran et al, 2014). According to the definition by the World Meteorological Organization (McInturff, 1978), a “minor” SSW occurs when a large temperature increase is observed in the winter polar stratosphere, at least by 25 K in a week or less. In the Southern Hemisphere (SH), the occurrence of an SSW, YAMAZAKI ET AL

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