September 2019 Antarctic sudden stratospheric warming: quasi-6-day wave
burst and ionospheric effects
Abstract
An 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 ESA’s Swarm satellite
constellation mission reveal 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 NASA’s Aura satellite show a burst of 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.