Influence of Stratosphere Polar Vortex Variability on the Mesosphere, Thermosphere, and Ionosphere

Abstract

During Northern Hemisphere winter, the stratosphere polar vortex that forms at high-latitudes in the Northern Hemisphere exhibits considerable variability. The stratosphere polar vortex variability is largely due to the presence, or absence, of planetary wave activity. During periods of strong planetary wave activity, the stratosphere polar vortex is weakened, leading to the occurrence of sudden stratosphere warming (SSW) events (Matsuno, 1971). Though identified based on changes in the stratosphere, SSWs have a wide range of impacts throughout the atmosphere (Baldwin et al., 2020;.In the mesosphere and lower thermosphere (MLT), SSW events are associated with changes in the circulation, mean winds, and atmospheric tides. At middle to high latitudes in the Northern Hemisphere, the zonal winds in the MLT reverse direction during SSWs (Hoffmann et al., 2007;Liu & Roble, 2002), which is primarily attributed to changes in gravity wave forcing (Limpasuvan et al., 2016;Liu & Roble, 2002;Zülicke et al., 2018). These zonal wind changes can extend across the equator into the Southern Hemisphere MLT through inter-hemispheric coupling (Körnich & Becker, 2010;Smith et al., 2020). The zonal mean zonal wind changes that occur during SSWs leads to enhancements in the migrating solar (SW2) and lunar (M2) semidiurnal tides (Chau et al., 2015;N. M. Pedatella et al., 2012;Zhang & Forbes, 2014). The SW2 is also enhanced due to changes in ozone forcing during SSWs (Siddiqui et al., 2019). Additional tidal variability occurs in non-migrating semidiurnal tides due to the non-linear interactions between the migrating tides and enhanced planetary wave activity (He et al., 2017;Liu et al., 2010;N. M. Pedatella & Liu, 2013). The changes in wave forcing during SSWs, including from gravity waves, planetary waves, and tides, alter the mean circulation of the MLT. During SSWs, the MLT circulation is characterized by enhanced clockwise and anti-clockwise circulation patterns in the Northern and Southern Hemispheres, respectively (

Long‐Term Variability and Tendencies in Mesosphere and Lower Thermosphere Winds From Meteor Radar Observations Over Esrange (67.9°N, 21.1°E)

“…In the westward phase of the QBO, the stratospheric polar vortex is more perturbed by PWs, resulting in weaker vortex. Recently, Pedatella (2023) simulated the influence of stratospheric polar vortex variability on the MLT winds/circulation. He reported that the MLT circulation is influenced strongly due to both strong and weak polar vortices.…”

Impact of the Polar Vortex on Sub‐Seasonal O/N2 Variability in the Lower Thermosphere Using GOLD and WACCM‐X

“…Figure 4b1 is the same except that one additional criterion: NAM ≥ 2.5 or NAM ≤ 2.1 (hereafter referred to as "anomalous vortex") is used. The 6-day time lag was chosen because it maximizes the correlations here, which is consistent with a time lag of approximately 1 week used in Pedatella (2023) for the PV modulation on O/N 2 in WACCM-X. The second row is the same as the first one except for using WACCM-X data from winters of 2010-2022, with the same analysis as applied to the GOLD data.…”

“…Recently, Pedatella (2023) demonstrated the influence of the PV (outside SSW) on O/N 2 from a modeling standpoint by finding positive correlations between the NAM index and O/N 2 residuals extracted from an ensemble of 40 northern hemisphere winters simulated by the Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM‐X) in its free‐running mode. Additionally, Greer et al.…”

“…Recently, Pedatella (2023) demonstrated the influence of the PV (outside SSW) on O/N 2 from a modeling standpoint by finding positive correlations between the NAM index and O/N 2 residuals extracted from an ensemble of 40 northern hemisphere winters simulated by the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) in its free-running mode. Additionally, Greer et al (2023) performed a case study of the response of O/N 2 , among other ionospheric and thermospheric parameters, to PV variability during one period of weak vortex activity (February 2008) and one period of strong vortex activity (February 2021) using data from the Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED) Global UltraViolet Imager (GUVI) instrument.…”

“…Here, we quantify the contribution of the PV to the variability of O/N 2 in the IT using observations from the Global Observations of the Limb and Disk (GOLD) instrument for all winters from December 2018 to February 2023, with a goal of providing observational support for the simulation results of Pedatella (2023) and statistical support for the observational results of Greer et al (2023). From a modeling standpoint, we further investigate the dependence of residual MMC on PV activity.…”