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Eastward‐Propagating Planetary Waves Prior to the January 2009 Sudden Stratospheric Warming
Author(s) -
Rhodes Christian T.,
Limpasuvan Varavut,
Orsolini Yvan J.
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033696
Subject(s) - stratosphere , sudden stratospheric warming , mesosphere , atmospheric sciences , gravity wave , wavenumber , atmosphere (unit) , forcing (mathematics) , polar vortex , climatology , environmental science , geology , physics , gravitational wave , meteorology , astrophysics , optics
Eastward‐propagating planetary waves (EPWs) were investigated prior to the boreal January 2009 major sudden stratospheric warming (SSW) event simulated by the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model with specified dynamics. About 22 days before SSW onset, a background flow with jet maxima around the upper polar stratosphere and subtropical mesosphere developed due to the net forcing by gravity and planetary waves. The mesospheric wind structure was largely unstable and supported a wave geometry conducive to overreflection. With a zonal phase speed of ∼10 m s −1 , EPWs appeared near their turning and critical layers as wavenumber‐2 perturbations in the stratosphere and mesosphere. Accompanied by upward EPW activity from the lower stratosphere, EPW growth exhibited characteristics of wave instability and overreflection.