Quasi‐biennial oscillation modulation of the middle‐ and high‐latitude mesospheric semidiurnal tides during August–September

Abstract

The seasonal and interannual variabilities of mesospheric semidiurnal tides (SDT) are investigated using specular meteor radar‐based winds. The horizontal wind observations during 2003 to 2014 from a high‐latitude station, Andenes (69°N, 16°E), and during 2008 to 2014 from a midlatitude station, Juliusruh (54°N, 13°E), are used. It has been observed that the amplitudes of mesospheric SDTs are enhanced at both stations during August–September of all the years. These enhancements show a systematic behavior with that of the low‐latitude stratospheric quasi‐biennial oscillation (QBO), which is characterized based on winds from radiosonde data. The SDT amplitude values during enhancement are below/above mean level for those years in which the QBO wind at 50 hPa is westward/eastward (QBOw/QBOe). The average SDT amplitudes during the August–September enhancement duration are found to vary hand in hand with the low‐latitude QBO wind, suggesting QBO modulation of SDT. Stratospheric and lower mesospheric zonal wind perturbations from MERRA reanalysis data show weak local forcing in the Northern Hemisphere and indication of enhanced quasi‐stationary planetary waves (SPW) in the Southern Hemisphere. Based on these observations and some earlier results, we hypothesize that the QBOw/QBOe wind damp/enhance the southern hemispheric SPW of wave number 1 (SPW1). This modulated SPW1 then interacts with the northern midlatitude and high‐latitude SDTs to imprint the signature of QBO on them.

Whole Atmosphere Coupling on Intraseasonal and Interseasonal Time Scales: A Potential Source of Increased Predictive Capability

“…For example, the signatures of both the gravest migrating solar tides DW1 and SW2 in mesospheric winds show enhanced amplitudes in the tropics during the eastward QBO phase and reduced amplitudes during the westward QBO phase (Davis et al, ; Vincent et al, ; Wu et al, ). Similar QBO modulations of both DW1 and SW2 throughout the MLT have been observed at middle and high latitudes of both hemispheres in both horizontal winds (e.g., Dhadly et al, ; Hibbins et al, ; Laskar et al, ) and temperatures (e.g., Pancheva et al, ; Xu et al, ). Nonmigrating tides have also been shown to be affected by the QBO (e.g., Gan et al, ; Oberheide et al, ; Wu et al, ), most notably the nonmigrating DE3 tide, which tends to be larger during QBO westward phase.…”

Mesospheric semidiurnal tides and near-12 h waves through jointly analyzing observations of five specular meteor radars from three longitudinal sectors at boreal midlatitudes

“…Here, nonmajor SSW events refer to the minor and final SSWs (cf. Butler et al, 2015Butler et al, , 2017Limpasuvan et al, 2005). The only exception in this classification is the 2015 event.…”

Interhemispheric Meridional Circulation During Sudden Stratospheric Warming

“…All these evidences clearly indicate that the dynamics and chemistry over the whole globe is perturbed enormously during SSW, and thus, there could occur direct interhemispheric coupling (IHC). There are many modeling, observational, and assimilation studies that showed general IHCs from winter stratosphere to the summer mesosphere (e.g., Becker & Fritts, 2006;France et al, 2018;Karlsson & Becker, 2016;Laskar et al, 2016;Murphy et al, 2012), which were interpreted mainly through wave-dynamical changes. There are many modeling, observational, and assimilation studies that showed general IHCs from winter stratosphere to the summer mesosphere (e.g., Becker & Fritts, 2006;France et al, 2018;Karlsson & Becker, 2016;Laskar et al, 2016;Murphy et al, 2012), which were interpreted mainly through wave-dynamical changes.…”