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During the 2023/2024 austral summer, the quasi‐two‐day (QTDW) with westward zonal wavenumber 3 (W3) abnormally reached its maximum amplitude at the December solstice (22 December 2023) for the first time in 20 years of Aura Microwave Limb Sounder observations, while the strongest event during austral summer usually occurs ∼2–6 weeks after the December solstice (on average January 21). Diagnostic analysis reveals that the westward winds in the Southern (summer) Hemisphere were anomalously strong (maximum of ∼90 m/s) during December 2023, which significantly shortened the e‐folding time of QTDW‐W3, and additionally generated the QTDW‐W3 critical layers at the tropical summer stratopause from December 7. These two factors contributed to the earliest amplification of QTDW‐W3. In essence, the cold equatorial stratosphere triggered the exceptionally strong westward winds in the Southern Hemisphere via thermal wind balance, which was related to the enhanced upward middle‐atmosphere Hadley circulation during a prolonged Arctic stratopause warming event. Plain Language Summary As one of the prominent dynamic features in the Earth's summer middle and upper atmosphere, the quasi‐two‐day wave (QTDW) with westward zonal wavenumber 3 (W3) has significant influences on the global zonal‐mean circulation and temperature. Long‐term satellite and ground‐based observations have shown that the QTDW‐W3 is stably amplified twice yearly after the solstice, namely January/February in the Southern Hemisphere and July/August in the Northern Hemisphere. Such climatological features are very sensitive to the spatial distribution of the zonal‐mean zonal wind in the summer stratosphere and mesosphere. This study focuses on the unusual amplification of QTDW‐W3 just at the December solstice during the recent austral summer of 2023/2024, which has been never observed in the past 20 years of Aura Microwave Limb Sounder observations. Further analysis indicates that this earliest amplification of QTDW‐W3 was induced by a persistent and dramatic stratopause warming event in the Arctic (winter) stratosphere during December 2023, which caused the westward winds in the Southern (summer) Hemisphere to be anomalously strong via secondary Rossby wave‐induced interhemispheric coupling process. The current results first reveal that stratopause warming also has great potential to alter the global middle and upper atmospheric dynamics like the famous sudden stratospheric warming. Key Points The quasi‐two‐day wave (QTDW) with s=3$s=3$(W3) was maximized at the December solstice for the first time during the 2023/2024 austral summer The burst window for QTDW‐W3 appeared 2 weeks earlier than usual due to the anomalously strong summer westward winds in December 2023 The prolonged winter stratopause warming in December 2023 greatly enhanced the summer westward winds by cooling the equatorial stratosphere

The state of the mesosphere is connected to the lower atmosphere through various dynamical coupling processes. Nine years of Odin satellite observations of noctilucent clouds (NLC) have been analyzed as tracers for such processes. Inter‐hemispheric coupling from the winter stratosphere and troposphere is confirmed to have a major influence on the summer mesosphere. Intra‐hemispheric coupling from the spring/summer stratosphere, on the other hand, can control the onset of the NLC season. Most prominently, the southern NLC season 2010–2011 started with a delay of more than 20 days as compared to other years, which coincides with an exceptionally persistent polar vortex in the Antarctic stratosphere. Proposed mechanisms for the above teleconnections are based on the effect of lower atmospheric circulation on gravity wave filtering and, thus, on the dynamical forcing of the mesospheric circulation. Both intra‐ and inter‐hemispheric coupling processes are needed for an understanding of the overall seasonal behavior of the summer mesosphere. Key Points Interhemispheric coupling modulates the polar summer mesosphere The polar vortex can delay the mesospheric summer circulation Both inter‐ and intrahemispheric coupling affect noctilucent clouds

We derive the correlation patterns over the global latitudes and from the stratosphere to lower thermosphere (broadly referred to as teleconnection) using temperature data measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) from 2002 to 2010, and using 54 years of simulations of temperatures and winds by the Whole Atmosphere Community Climate Model (WACCM). We also analyze the possible mechanisms of teleconnection by investigating the correlations between the temperature and residual circulation. The correlation patterns show that teleconnection exists globally over the equatorial, mid‐ and high‐latitudes, and temperature anomalies correspond well to the anomalies of the residual circulations through adiabatic heating/cooling. A main new finding of this study is that the teleconnection extends well into the lower thermosphere, the thermospheric anomalies are consistent with the corresponding changes of the winter‐to‐summer lower‐thermospheric branch of the residual circulation, and the winter stratosphere perturbations influence the thermosphere globally. Using a reference point chosen in the northern winter stratosphere, we find that the teleconnection structures for time periods with and without Sudden Stratospheric Warmings (SSWs) display similar patterns in SABER, and teleconnection patterns in WACCM are nearly identical for days with major SSWs, minor SSWs and without SSWs. WACCM results show strong inter‐annual and intra‐annual altitude variations of the teleconnection patterns in the southern polar region but stable altitudes of correlation regions in the equatorial and northern latitudes. The altitude variations are likely responsible for the weak correlations poleward of 60°S when multiyear or multimonth data are used. Key Points Teleconnection exists globally and extends well into the thermosphere Temperature anomalies are correlated with anomalies of three circulations Major, minor and no SSWs show similar teleconnection patterns

Polar mesospheric cloud (PMC) observations have revealed that interannual variability near the polar summer mesopause can be forced by planetary wave activity in the winter stratosphere. We use data from the Aeronomy of Ice in the Mesosphere (AIM) satellite to investigate coupling between the Arctic winter stratosphere and PMC variability in the Antarctic summer of 2007–2008. We find a high correlation between zonal mean PMC frequency and Arctic winter zonal mean winds from the Goddard Earth Observing System, as well as Microwave Limb Sounder zonal mean temperatures. The time lag between changes in the winter stratosphere and the connected response in PMCs varies from 2 to 8 days. We suggest that the differences in lag times are related to the evolution of cloud altitudes throughout the season. The results here are the first to show evidence for intra‐seasonal PMC variability forced by inter‐hemispheric coupling.

Electroencephalography was performed in 7-8- and 9-10-year-old pupils. Control group consisted of healthy children; experimental group consisted of children without signs of grade IV and V sinus arrhythmia at the age of 7-8 years, but with grade IV and V sinus arrhythmia at the age of 9-10 years. In primary school-aged children (7-8 years), manifestation of marked sinus arrhythmia is associated with disturbances in age-specifi c dynamics of interhemispheric interaction and with the formation, at the initial stage, of a rigid integrated system primarily due to functional intrahemispheric connections, the major contribution being made by the posterior associative cortical areas.

This study aims to characterize the interhemispheric teleconnection pattern, which is established by the South America (SA) summer monsoon over the Atlantic Ocean during January and February, and referred it as the Atlantic symmetric pattern (ASP). The ASP is characterized using the leading mode of interannual sea surface temperature (SST) variability of the Southwest Atlantic Ocean, where strong convection-SST coupling occurs. The pattern is manifested as two anomalous cyclonic-anticyclonic-cyclonic circulation trains aligned meridionally over the Atlantic Ocean, with a distinct SST dipole of the Southwest Atlantic Ocean and a tripole of the North Atlantic Ocean. The interhemispheric wave trains of the ASP are excited as a Gill-type response to convective activity in the SA summer monsoon, as confirmed in linear baroclinic model. Complementing previous studies on observed interhemispheric connection in the Atlantic, our findings highlight the importance of characterizing the ASP and its role in linking the South Atlantic SST, the SA summer monsoon, and North Atlantic climate. Further research is warranted to explore the impacts of the ASP on the Northern Hemisphere and its interactions with other climatic modes.

There is converging evidence that bilateral basal ganglia motor networks jointly support normal movement behaviors including unilateral movements. The extent and manner in which these networks interact during lateralized movement remains unclear. In this study, simultaneously recorded bilateral Globus Pallidus interna (GPi) local field potentials (LFP) were examined from 19 subjects with idiopathic Parkinson disease (PD), while undergoing awake deep brain stimulation (DBS) implantation. Recordings were carried out during two behavioral states; rest and cued left hand movement (finger tapping). The state-dependent effects on α- β oscillatory power and β phase-encoded phase amplitude coupling (PAC), including symmetrical and assymetrical changes between hemispheres, were identified. Unilateral hand movement resulted in symmetrical oscillatory power suppression within bilateral GPi at α (8-12 Hz) and high β (21-35 Hz) and increase in power of high frequency oscillations (HFO, 200-300 Hz) frequency bands. Asymmetrical attenuation was also observed at both low β (13-20 Hz) and low γ (40-80 Hz) bands within the contralateral GPi ( = 0.009). In addition, unilateral movement effects on PAC were confined to the contralateral GPi with attenuation of both low β-low γ and β-HFO PAC ( < 0.05). Further analysis showed that the lateralized attenuation of low β and low γ power did not correlate with low β-low γ PAC changes. The overall coherence between bilateral GPi was not significantly altered with unilateral movement, however the preferred phase difference in the high β range increased from 0.23 (±1.31) radians during rest to 1.99 (±0.78) radians during movement execution. Together, the present results suggest that unilateral motor control involves bilateral basal ganglia networks with movement features differentially encoded by distinct frequency bands. The lateralization of low β and low γ attenuation with movement suggests that these frequency bands are specific to the motor act whereas symmetrical expression of α, high β, and HFO oscillations best correspond to motor state. The restriction of movement-related PAC modulation to the contralateral GPi indicates that cross-frequency interactions appear to be associated with lateralized movements. Despite no significant movement-related changes in the interhemispheric coherence, the increase in phase difference suggests that the communication between bilateral GPi is altered with unilateral movement.

The ionosphere exhibits some characteristic perturbations during sudden stratospheric warming (SSW) events, of which the mechanism is not thoroughly understood. This study focuses on the latitudinal and interhemispheric differences of the enhanced semi-diurnal lunitidal (M2) perturbations related to SSW using total electron content calculated from the network of Global Navigation Satellite System and ionosonde data in the eastern Asia–Australia sector during the January 2009 SSW. Our results show that the most distinct M2 perturbations in the northern and southern hemispheres occur near the Equatorial Ionization Anomaly crest regions around ± 15° geomagnetic latitudes, but corresponds to different moon phases, respectively. Clear M2 perturbations extend to middle latitudes only in the southern hemisphere and have another local maximum in the southern middle latitude. Such latitudinal and interhemispheric features of ionospheric M2 perturbations in the low latitude in the eastern Asia–Australia sector are similar as those in the American sector during the same SSW event. This supports previous suggestion that such latitudinal and interhemispheric differences in the low latitude can be primarily explained by the summer–winter thermospheric wind modulation on equatorial plasma fountain and thus emphasize its role in the vertical coupling process of M2 perturbation. The clear differences of M2 perturbations in the southern middle latitude between the eastern Asia–Australia and American sectors indicate that the thermospheric circulation related to the Weddell Sea Anomaly may have influence on the lower atmosphere–ionosphere coupling.

Wind observations obtained between 1995 and 2011 using the MF radar at Davis have been used to demonstrate the modifying role the quasi‐biennial oscillation (QBO) plays on some aspects of interhemispheric coupling identified by previous authors. The response of the meridional wind in the southern summer polar MLT to changes in winter stratospheric planetary wave activity is shown to change sign according to the phase of the QBO. The time delay associated with the coupling is also shown to vary with QBO phase, with an eastward QBO providing a more rapid response. Coupling to the MLT meridional winds is strongest in January. Parts of the mechanism currently proposed have been tested using UKMO assimilated observations. The signatures of some aspects of this mechanism are present in the data. However, some differences to the mechanism are also apparent, in particular the effectiveness of the mechanism near the equator. An explanation for the QBO modulation of the MLT wind response to interhemispheric coupling is proposed on the basis of these differences. Key Points Coupling from winter stratosphere to summer polar MLT identified in wind QBO found to modulate the interhemispheric coupling mechanism

Several functional magnetic resonance imaging (fMRI) studies of acute stroke have reported that patients with behavioral deficits show abnormal signal in intact regions of the damaged hemisphere close to the lesion border relative to homologous regions of the patient's intact hemisphere (causing an interhemispheric imbalance) as well as analogous regions in healthy controls. These effects have been interpreted as demonstrating a causal relationship between the abnormal fMRI signal and the pathological behavior. Here we explore an alternative explanation: perhaps the abnormal Blood-Oxygenation Level Dependent (BOLD) fMRI signal is merely a function of distance from the acute lesion. To investigate this hypothesis, we examined three patients with an acute right hemisphere cortical stroke who did not show any overt behavioral deficits, as well as nine healthy elderly controls. We acquired fMRI data while the participants performed a simple visual orientation judgment task. In patients, we observed an abnormal interhemispheric balance consisting of lower levels of percent signal change in perilesional areas of the damaged hemisphere relative to homologous areas in neurologically healthy controls. This suggests that the physiological changes and corresponding interhemispheric imbalance detected by fMRI BOLD in acute stroke observed close to the lesion border may not necessarily reflect changes in the neural function, nor necessarily influence the individuals' (e.g., attentional) behavior.