This study employs Principal Component Analysis(PCA)and 13 years of SD-WACCM-X model data(2007-2019)to investigate the characteristics and mechanisms of Inter-hemispheric Coupling(IHC)triggered by sudden stratospheric...This study employs Principal Component Analysis(PCA)and 13 years of SD-WACCM-X model data(2007-2019)to investigate the characteristics and mechanisms of Inter-hemispheric Coupling(IHC)triggered by sudden stratospheric warming(SSW)events.IHC in both hemispheres leads to a cold anomaly in the equatorial stratosphere,a warm anomaly in the equatorial mesosphere,and increased temperatures in the mesosphere and lower thermosphere(MLT)region of the summer hemisphere.However,the IHC features during boreal winter period are significantly weaker than during the austral winter period,primarily due to weaker stationary planetary wave activity in the Southern Hemisphere(SH).During the austral winter period,IHC results in a warm anomaly in the polar mesosphere of the SH,which does not occur in the NH during boreal winter period.This study also examines the possible influence of quasi-two-day waves(QTDWs)on IHC.We found that the largest temperature anomaly in the summer polar MLT region is associated with a large wind instability area,and a well-developed critical layer structure of QTDW in January.In contrast,during July,despite favorable conditions for QTDW propagation in the Northern Hemisphere,weaker IHC response is observed,suggesting that IHC features and the relationship with QTDWs during July would be more complex than during January.展开更多
Air mass is inter-hemispherically redistributed, leading to an interesting phenomenon known as the Inter-Hemispheric Oscillation （IHO）. In the present article, the seasonality of the interannual IHO has been examine...Air mass is inter-hemispherically redistributed, leading to an interesting phenomenon known as the Inter-Hemispheric Oscillation （IHO）. In the present article, the seasonality of the interannual IHO has been examined by employing monthly mean reanalyses from NCEP/NCAR, EAR40, and JRA25 for the period of 1958–2006. It is found that the IHO indices as calculated from different reanalyses are generally consistent with each other. A distinct seesaw structure in all four seasons between the northern and southern hemispheres is observed as the IHO signature in both the surface air pressure anomalies （SAPAs） and the leading EOF component of the anomalous zonal mean quantities. When the SAPAs are positive （negative） in the northern hemisphere, they are negative （positive） in the southern hemisphere. Large values of SAPAs are usually observed in mid- and high-latitude areas in all but the solstice seasons. In boreal summer and winter, relatively stronger perturbations of IHO-related SAPA are found in the Asian monsoon region, which shows a large difference from the status in boreal spring and fall. This suggests that seasonal mean monsoon activity is globally linked via air mass redistribution globally on interannual timescales, showing a very interesting linkage between monsoons and the IHO in the global domain. In all seasons, large values of SAPA always exist over the Antarctic and the surrounding regions, implying a close relation with Antarctic oscillations.展开更多
The identification of individual factors modulating clinical recovery after a stroke is fundamental to personalize the therapeutic intervention to enhance the final clinical outcome.In this framework,electrophysiologi...The identification of individual factors modulating clinical recovery after a stroke is fundamental to personalize the therapeutic intervention to enhance the final clinical outcome.In this framework,electrophysiological factors are promising since are more directly related to neuroplasticity,which supports recovery in stroke patients,than neurovascular factors.In this retrospective observational study,we investigated brain neuronal activity assessed via spectral features and Higuchi's fractal dimension(HFD) of electroencephalographic signals in acute phase(2–10 days from symptom onset,T0) and sub-acute phase(2.5 months,T1) in 24 patients affected by unilateral middle cerebral artery stroke.Longitudinal assessment of the clinical deficits was performed using the National Institutes of Health Stroke Scale(NIHSS),together with the effective recovery calculated as the ratio between difference of NIHSS at T0 and T1 over the NIHSS value at T0.We observed that delta and alpha band electroencephalographic signal power changed between the two phases in both the hemispheres ipsilateral(ILH) and contralateral(CHL) to the lesion.Moreover,at T0,bilateral higher delta band power correlated with worse clinical conditions(Spearman's rs = 0.460,P = 0.027 for ILH and rs = 0.508,P = 0.013 for CLH),whereas at T1 this occurred only for delta power in ILH(rs = 0.411,P = 0.046) and not for CHL.Inter-hemispheric difference(ILH vs.CLH) of alpha power in patients was lower at T0 than at T1(P = 0.020).HFD at T0 was lower than at T1(P = 0.005),and at both phases,ILH HFD was lower than CLH HFD(P = 0.020).These data suggest that inter-hemispheric low band asymmetry and fractal dimension changes from the acute to the sub-acute phase are sensitive to neuroplasticity processes which subtend clinical recovery.The study protocol was approved by the Bioethical Committee of Ospedale San Giovanni Calibita Fatebenefretelli(No.40/2011) on July 14,2011.展开更多
A numerical investigation of diabatically induced stationary waves in northern winter season was carried out by using a linear steady state spectral model with primitive equations in global domain. It was focused on i...A numerical investigation of diabatically induced stationary waves in northern winter season was carried out by using a linear steady state spectral model with primitive equations in global domain. It was focused on inter-hemispheric connections of stationary wave behaviour in response to several cases of idealized thermal forcings centred in different latitudes. The results showed that the thermally forced stationary waves in one hemisphere might propagate across the equator into the other hemisphere, and thus contribute substantially to the maintenance and variation of the stationary waves in both bendspheres.展开更多
基金supported by the National Natural Science Foundation of China(Grant Numbers 42374195 and 42188101)the fellowship of China National Postdoctoral Program for Innovative Talents(Grant Number BX20230273)+1 种基金the Hubei Provincial Natural Science Foundation of China(Grant Number 2024AFB-097)the Postdoctor Project of Hubei Province(Grant Number 2024HBBHCXA054).
文摘This study employs Principal Component Analysis(PCA)and 13 years of SD-WACCM-X model data(2007-2019)to investigate the characteristics and mechanisms of Inter-hemispheric Coupling(IHC)triggered by sudden stratospheric warming(SSW)events.IHC in both hemispheres leads to a cold anomaly in the equatorial stratosphere,a warm anomaly in the equatorial mesosphere,and increased temperatures in the mesosphere and lower thermosphere(MLT)region of the summer hemisphere.However,the IHC features during boreal winter period are significantly weaker than during the austral winter period,primarily due to weaker stationary planetary wave activity in the Southern Hemisphere(SH).During the austral winter period,IHC results in a warm anomaly in the polar mesosphere of the SH,which does not occur in the NH during boreal winter period.This study also examines the possible influence of quasi-two-day waves(QTDWs)on IHC.We found that the largest temperature anomaly in the summer polar MLT region is associated with a large wind instability area,and a well-developed critical layer structure of QTDW in January.In contrast,during July,despite favorable conditions for QTDW propagation in the Northern Hemisphere,weaker IHC response is observed,suggesting that IHC features and the relationship with QTDWs during July would be more complex than during January.
基金supported jointlyby the National Key Technology R&D Program (GrantNo. 2007BAC29B02)the National Natural Science Foundation of China (NSFC, Grant No. 40675025)the Key Laboratory of Meteorological Disasters, Nanjing University of Information Science & Technology (NUIST,KLME060101)
文摘Air mass is inter-hemispherically redistributed, leading to an interesting phenomenon known as the Inter-Hemispheric Oscillation （IHO）. In the present article, the seasonality of the interannual IHO has been examined by employing monthly mean reanalyses from NCEP/NCAR, EAR40, and JRA25 for the period of 1958–2006. It is found that the IHO indices as calculated from different reanalyses are generally consistent with each other. A distinct seesaw structure in all four seasons between the northern and southern hemispheres is observed as the IHO signature in both the surface air pressure anomalies （SAPAs） and the leading EOF component of the anomalous zonal mean quantities. When the SAPAs are positive （negative） in the northern hemisphere, they are negative （positive） in the southern hemisphere. Large values of SAPAs are usually observed in mid- and high-latitude areas in all but the solstice seasons. In boreal summer and winter, relatively stronger perturbations of IHO-related SAPA are found in the Asian monsoon region, which shows a large difference from the status in boreal spring and fall. This suggests that seasonal mean monsoon activity is globally linked via air mass redistribution globally on interannual timescales, showing a very interesting linkage between monsoons and the IHO in the global domain. In all seasons, large values of SAPA always exist over the Antarctic and the surrounding regions, implying a close relation with Antarctic oscillations.
基金FZ and FT obtained financial support from the Italian Ministry of Health Cod.GR-2008-1138642 "Promoting recovery from Stroke:individually enriched therapeutic intervention in Acute phase"PNR-CNR Aging Program
文摘The identification of individual factors modulating clinical recovery after a stroke is fundamental to personalize the therapeutic intervention to enhance the final clinical outcome.In this framework,electrophysiological factors are promising since are more directly related to neuroplasticity,which supports recovery in stroke patients,than neurovascular factors.In this retrospective observational study,we investigated brain neuronal activity assessed via spectral features and Higuchi's fractal dimension(HFD) of electroencephalographic signals in acute phase(2–10 days from symptom onset,T0) and sub-acute phase(2.5 months,T1) in 24 patients affected by unilateral middle cerebral artery stroke.Longitudinal assessment of the clinical deficits was performed using the National Institutes of Health Stroke Scale(NIHSS),together with the effective recovery calculated as the ratio between difference of NIHSS at T0 and T1 over the NIHSS value at T0.We observed that delta and alpha band electroencephalographic signal power changed between the two phases in both the hemispheres ipsilateral(ILH) and contralateral(CHL) to the lesion.Moreover,at T0,bilateral higher delta band power correlated with worse clinical conditions(Spearman's rs = 0.460,P = 0.027 for ILH and rs = 0.508,P = 0.013 for CLH),whereas at T1 this occurred only for delta power in ILH(rs = 0.411,P = 0.046) and not for CHL.Inter-hemispheric difference(ILH vs.CLH) of alpha power in patients was lower at T0 than at T1(P = 0.020).HFD at T0 was lower than at T1(P = 0.005),and at both phases,ILH HFD was lower than CLH HFD(P = 0.020).These data suggest that inter-hemispheric low band asymmetry and fractal dimension changes from the acute to the sub-acute phase are sensitive to neuroplasticity processes which subtend clinical recovery.The study protocol was approved by the Bioethical Committee of Ospedale San Giovanni Calibita Fatebenefretelli(No.40/2011) on July 14,2011.
文摘A numerical investigation of diabatically induced stationary waves in northern winter season was carried out by using a linear steady state spectral model with primitive equations in global domain. It was focused on inter-hemispheric connections of stationary wave behaviour in response to several cases of idealized thermal forcings centred in different latitudes. The results showed that the thermally forced stationary waves in one hemisphere might propagate across the equator into the other hemisphere, and thus contribute substantially to the maintenance and variation of the stationary waves in both bendspheres.
