TY - JOUR
T1 - A synoptic view of the onset of the midlatitude QBO signal
AU - Silverman, Vered
AU - Lubis, Sandro W.
AU - Harnik, Nili
AU - Matthes, Katja
N1 - Publisher Copyright:
© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).
PY - 2021/11
Y1 - 2021/11
N2 - The extratropical effect of the quasi-biennial oscillation (QBO), known as the Holton-Tan effect, is manifest as a weaker, warmer winter Arctic polar vortex during the east QBO phase. While previous studies have shown that the extratropical QBO signal is caused by the modified propagation of planetary waves in the stratosphere, the mechanism dominating the onset and seasonal development of the Holton-Tan effects remains unclear. Here, the governing wave-mean flow dynamics of the early winter extratropical QBO signal onset and its reversibility is investigated on a synoptic time scale with a finite-amplitude diagnostic using reanalysis and a chemistry-climate model. The extratropical QBO signal onset in October is found to primarily result from modulated stratospheric life cycles of wave pulses entering the stratosphere from the troposphere, rather than from a modulation of their tropospheric wave source. A comprehensive analysis of the wave activity budget during fall, when the stratospheric winter polar vortex starts forming and waves start propagating up into the stratosphere, shows significant differences. During the east QBO phase, the deceleration of the mid-high-latitude stratospheric zonal-mean jet by the upward-propagating wave pulses is less reversible, due to stronger dissipation processes, while during the west phase, a more reversible deceleration of the main polar vortex is found owing to the waves being dissipated at lower latitudes, accompanied by a weak but different response of the tropospheric subtropical jet. From this synoptic wave-event viewpoint, the early season onset of the Holton-Tan effect results from the cumulative effect of the QBO dependent wave-induced deceleration during the life cycle of individual upward wave pulses.
AB - The extratropical effect of the quasi-biennial oscillation (QBO), known as the Holton-Tan effect, is manifest as a weaker, warmer winter Arctic polar vortex during the east QBO phase. While previous studies have shown that the extratropical QBO signal is caused by the modified propagation of planetary waves in the stratosphere, the mechanism dominating the onset and seasonal development of the Holton-Tan effects remains unclear. Here, the governing wave-mean flow dynamics of the early winter extratropical QBO signal onset and its reversibility is investigated on a synoptic time scale with a finite-amplitude diagnostic using reanalysis and a chemistry-climate model. The extratropical QBO signal onset in October is found to primarily result from modulated stratospheric life cycles of wave pulses entering the stratosphere from the troposphere, rather than from a modulation of their tropospheric wave source. A comprehensive analysis of the wave activity budget during fall, when the stratospheric winter polar vortex starts forming and waves start propagating up into the stratosphere, shows significant differences. During the east QBO phase, the deceleration of the mid-high-latitude stratospheric zonal-mean jet by the upward-propagating wave pulses is less reversible, due to stronger dissipation processes, while during the west phase, a more reversible deceleration of the main polar vortex is found owing to the waves being dissipated at lower latitudes, accompanied by a weak but different response of the tropospheric subtropical jet. From this synoptic wave-event viewpoint, the early season onset of the Holton-Tan effect results from the cumulative effect of the QBO dependent wave-induced deceleration during the life cycle of individual upward wave pulses.
KW - Eddies
KW - General circulation models
KW - Mixing
KW - Planetary waves
KW - Potential vorticity
KW - Quasibiennial oscillation
KW - Reanalysis data
KW - Rossby waves
KW - Stratosphere
KW - Stratosphere-troposphere coupling
KW - Stratospheric circulation
KW - Synoptic-scale processes
KW - Teleconnections
KW - Wave breaking
UR - http://www.scopus.com/inward/record.url?scp=85119457777&partnerID=8YFLogxK
U2 - 10.1175/JAS-D-20-0387.1
DO - 10.1175/JAS-D-20-0387.1
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AN - SCOPUS:85119457777
SN - 0022-4928
VL - 78
SP - 3759
EP - 3780
JO - Journal of the Atmospheric Sciences
JF - Journal of the Atmospheric Sciences
IS - 12
ER -