Quasi-10-day wave and semi-diurnal tide nonlinear interactions during
the southern hemispheric SSW 2019 observed in the northern hemispheric
mesosphere
Abstract
Mesospheric winds from three longitudinal sectors at about
65$^\circ$N and 54$^\circ$N
latitude are combined to diagnose the zonal wavenumbers ($m$) of
high-frequency-resolved spectral wave signatures during the rare
southern hemisphere sudden stratospheric warming (SSW) of 2019.
Diagnosed are quasi-10- and 6-day planetary waves (Q10DW and Q6DW,
$m$=1), solar semi-diurnal tides with $m$=1, 2, 3 (SW1, SW2, and
SW3), lunar semi-diurnal tide, and the upper and lower sidebands (USB
and LSB, $m$=1 and 3) of Q10DW-SW2 nonlinear interaction. We further
present a 7-year composite analysis to distinguish SSW effects from
climatological behaviors. Immediately before (after) the SSW onset, LSB
(USB) enhances, accompanied by the enhancing (fading) Q10DW, and a
weakening of climatological SW2 maximum. These behaviors are explained
in terms of Manley-Rowe energy relation, i.e., the energy goes first
from SW2 to Q10DW and LSB, and then from SW2 and Q10DW to USB.