基于1959～2013年的观测和再分析资料以及10.7 cm （2800MHz）太阳射电通量资料,本文分析了太阳活动变化与东亚冬季气候的相关关系,分析结果表明：太阳活动变化与东亚冬季大气环流有较好的相关性,且在太阳活动的强、弱时期该相关关系存...基于1959～2013年的观测和再分析资料以及10.7 cm （2800MHz）太阳射电通量资料,本文分析了太阳活动变化与东亚冬季气候的相关关系,分析结果表明：太阳活动变化与东亚冬季大气环流有较好的相关性,且在太阳活动的强、弱时期该相关关系存在很大差异,在强太阳活动时期太阳活动变化与东亚冬季气候的联系更为显著,而在弱太阳活动时期二者之间的直接联系微弱,这表明太阳活动变化对东亚冬季气候的影响具有非对称性特征.在太阳活动较强的时期,随着太阳活动的增强,东亚中高纬对流层中层的大气环流倾向纬向型,东亚大槽减弱,850 hPa出现异常偏南风,地面上西伯利亚高压以及冬季风减弱,东亚大部分地区气温显著偏高;而在太阳活动较弱的时期,太阳活动的年际差异与东亚冬季大气环流之间几乎不存在显著联系.分析太阳活动较强和较弱时期纬向平均纬向风的差异发现,其间平流层行星波活动、热带西北太平洋海表温度的差异可能是造成这种非对称影响的重要原因.在强太阳活动时期,平流层行星波在太阳活动的异常增强年有异常的从极地向赤道的水平传播,高纬地区E-P通量（Eliassen-Palm flux）异常辐散,导致中高纬西风及北极涛动（AO）增强,同时热带西北太平洋海温异常偏冷,海陆热力差异缩小,大气环流经向度减弱,东亚冬季风偏弱.展开更多
Using 1958-2002 NCEPNCAR reanalysis data, we investigate stationary and transient planetary wave propagation and its role in wave-mean flow interaction which influences the state of the polar vortex （PV） in the stra...Using 1958-2002 NCEPNCAR reanalysis data, we investigate stationary and transient planetary wave propagation and its role in wave-mean flow interaction which influences the state of the polar vortex （PV） in the stratosphere in Northern Hemisphere （NH） winter. This is done by analyzing the Eliassen-Palm （E-P） flux and its divergence. We find that the stationary and transient waves propagate upward and equatorward in NH winter, with stronger upward propagation of stationary waves from the troposphere to the stratosphere, and stronger equatorward propagation of transient waves from mid-latitudes to the subtropics in the troposphere. Stationary waves exhibit more upward propagation in the polar stratosphere during the weak polar vortex regime （WVR） than during the strong polar vortex regime （SVR）. On the other hand, transient waves have more upward propagation during SVR than during WVR in the subpolar stratosphere, with a domain of low frequency waves. With different paths of upward propagation, both stationary and transient waves contribute to the maintenance of the observed stratospheric PV regimes in NH winter.展开更多
The impact of La Ni?a on the winter Arctic stratosphere has thus far been an ambiguous topic of research. Contradictory results have been reported depending on the La Ni?a events considered. This study shows that this...The impact of La Ni?a on the winter Arctic stratosphere has thus far been an ambiguous topic of research. Contradictory results have been reported depending on the La Ni?a events considered. This study shows that this is mainly due to the decadal variation of La Ni?a’s impact on the winter Arctic stratosphere since the late 1970 s. Specifically,during the period1951–78,the tropospheric La Ni?a teleconnection exhibits a typical negative Pacific–North America pattern,which strongly inhibits the propagation of the planetary waves from the extratropical troposphere to the stratosphere,and leads to a significantly strengthened stratospheric polar vortex. In contrast,during 1979–2015,the La Ni?a teleconnection shifts eastwards,with an anomalous high concentrated in the northeastern Pacific. The destructive interference of the La Ni?a teleconnection with climatological stationary waves seen in the earlier period reduces greatly,which prevents the drastic reduction of planetary wave activities in the extratropical stratosphere. Correspondingly,the stratospheric response shows a less disturbed stratospheric polar vortex in winter.展开更多
基于无线电探空仪和掩星的对流层顶观测虽然可以揭示对流层顶高度和温度的一些特性,但是在某一个地点的时间分辨率较低,资料的时间分辨率几乎都是以天计,同时所获得的对流层顶信息也不能直接反映对流层顶的产生、发展和消亡过程.借助于...基于无线电探空仪和掩星的对流层顶观测虽然可以揭示对流层顶高度和温度的一些特性,但是在某一个地点的时间分辨率较低,资料的时间分辨率几乎都是以天计,同时所获得的对流层顶信息也不能直接反映对流层顶的产生、发展和消亡过程.借助于MST雷达具有高时间分辨率和连续性这一显著优势,实时、连续地获得对流层顶雷达回波,通过构建普适性雷达对流层顶判读模型,可以更好地研究对流层顶高度和结构形态的时空演化过程.探空仪对比实验表明:雷达方法观测对流层顶高度与气象学方法观测对流层顶高度相差约2 km,这应该和二者的探测机制相关.统计分析2012年全年雷达对流层顶回波差异值可以发现,雷达对流层顶高度的年平均值为13.3 km,标准差为0.65 km;对流层顶回波差异平均值约为11.7 d B,标准差为4.3 d B,雷达对流层顶回波差异值直接反映了雷达对流层顶结构的稀疏状态.同时本文利用Lomb-Scargle谱分析方法检测了对流层顶结构形态的扰动周期,结果表明大气潮汐波和行星波分量会影响对流层顶的结构形态.展开更多
The characteristics of high-latitude planetary waves (PWs) in the troposphere and lower stratosphere (TLS) are studied by using the data from radiosonde observations during 1998 to 2006 at three Alaskan stations in US...The characteristics of high-latitude planetary waves (PWs) in the troposphere and lower stratosphere (TLS) are studied by using the data from radiosonde observations during 1998 to 2006 at three Alaskan stations in USA (Nome, 64.50°N, 165.43°W; McGrath, 62.97°N, 155.62°W; Fairbanks, 64.82°N, 147.87°W). It is found that strong PWs exist in two regions. One is around tropopause, and the other is in the polar night jet (PNJ) in winter. The PW activities are rather intermittent, and their lifetimes are no longer than two months. Among three perturbation components in zonal and meridional winds and temperature, the temperature disturbance amplitude is the smallest, and the amplitude for the meridional wind component the largest. Around the tropopause, quasi 5-, 10-, and 16-day PW activities can be observed simultaneously. Among these PW components, the quasi 5-day and 10-day PW are the weakest and strongest, respectively. Moreover, PWs around the tropopause are complex and no obvious season variability can be observed. However, in the PNJ, the higher region, only obvious quasi 10-day and 16-day PWs remain, with smaller amplitudes than those around the tropopause. And significant PWs in the PNJ occur only in winter. By calculating the refractive index for PWs, it is found that there is a persistent reflection layer around 11 km, which is thick in summer and becomes thin or even disappears in winter, revealing that PWs in the stratosphere can only occur in winter. PWs in the 2003/2004 winter at the three stations are analyzed in detail. It is found that for the focused observation duration, the quasi 10-day and quasi 16-day waves exist mainly in the troposphere and stratosphere, respectively. The quasi 10-day wave is a standing wave in the vertical direction, with vertical wavelength about 12 km in the temperature component and larger than 26 km in the meridional component. Moreover, the tropospheric quasi 10-day wave propagates westward with the zonal numbers between 2 and 4. The quasi 16-day wave is also a stand展开更多
In this paper, the variations of the mean flow, the E-P flux and its divergence of planetary waves in the process of the formation, maintenance and collapse of the blocking situation in the second half of February, 19...In this paper, the variations of the mean flow, the E-P flux and its divergence of planetary waves in the process of the formation, maintenance and collapse of the blocking situation in the second half of February, 1979 are analysed with the transformed Eulerian mean-motion equations.Analysed results show that because the basic flow changes from the easterly into the westerly in the lower troposphere at high latitudes, the planetary wave for wavenumber 2 strongly propagates upwards, and because of the interaction between the upward propagating planetary wave and the basic flow, the westerty is weakened and approaches to the resonant flow of wavenumber 2 in the middle and upper troposphere (then, in the lower and middle Stratosphere). This may cause the anomalous amplification of planetary wave for wavenumber 2, and moreover make the mean flow change from the westerly into the easterly in the lower and middle stratosphere, following the upper troposphere. Therefore, the blocking situation can be formed and maintained on the Northern Hemisphere. Thus, the upward propagations of quasi-stationary planetary waves and the mutual interaction with the basic flow are also one of the reasons of the formation and maintenance of the blocking situation.展开更多
A linear,hemispheric and stationary spectral model with multilayers in the vertical was employed to simulate the vertical propagation of waves triggered by mountains.Results show that,in cooperation with the East Asia...A linear,hemispheric and stationary spectral model with multilayers in the vertical was employed to simulate the vertical propagation of waves triggered by mountains.Results show that,in cooperation with the East Asia zonal mean flow,Tibetan Plateau can excite a strong wavenumber 1 perturbation in the stratosphere with its ridge and trough lo- cated over the Pacific and Atlantic Oceans respectively.On the other hand,the stratospheric wavenumber 1 perturbation caused by the mechanical forcing of the Rocky Mountains in cooperation with the North America zonal mean flow is very weak.Calculations from observational data of the vertical profile of critical wavenumber for vertically propagating waves imply that the tropospheric wavenumber 1 perturbation can hardly penetrate the North America tropopause up- wards,whereas it can freely propagate through the East Asia tropopause into the stratosphere.Two-dimensional E-P cross-sections obtained from both observational data and simulated results also demonstrate that waves excited by the Rocky Mountains are refracted towards low latitudes in the troposphere during their upward propagation:whereas,in addition to the above mentioned equatorward leaning branch,the wavenumber 1 and 2 planetary waves excited by the Tibetan Plateau possess another branch which is refracted to high latitudes during upward propagation and penetrates the tropopause into the stratosphere.It is therefore concluded that the difference in the horizontal and vertical wave propagations in the two hemispheres is a result of the different dynamical forcing induced by the two main mountains in the Northern Hemisphere.展开更多
文摘基于1959～2013年的观测和再分析资料以及10.7 cm （2800MHz）太阳射电通量资料,本文分析了太阳活动变化与东亚冬季气候的相关关系,分析结果表明：太阳活动变化与东亚冬季大气环流有较好的相关性,且在太阳活动的强、弱时期该相关关系存在很大差异,在强太阳活动时期太阳活动变化与东亚冬季气候的联系更为显著,而在弱太阳活动时期二者之间的直接联系微弱,这表明太阳活动变化对东亚冬季气候的影响具有非对称性特征.在太阳活动较强的时期,随着太阳活动的增强,东亚中高纬对流层中层的大气环流倾向纬向型,东亚大槽减弱,850 hPa出现异常偏南风,地面上西伯利亚高压以及冬季风减弱,东亚大部分地区气温显著偏高;而在太阳活动较弱的时期,太阳活动的年际差异与东亚冬季大气环流之间几乎不存在显著联系.分析太阳活动较强和较弱时期纬向平均纬向风的差异发现,其间平流层行星波活动、热带西北太平洋海表温度的差异可能是造成这种非对称影响的重要原因.在强太阳活动时期,平流层行星波在太阳活动的异常增强年有异常的从极地向赤道的水平传播,高纬地区E-P通量（Eliassen-Palm flux）异常辐散,导致中高纬西风及北极涛动（AO）增强,同时热带西北太平洋海温异常偏冷,海陆热力差异缩小,大气环流经向度减弱,东亚冬季风偏弱.
基金supported by the National Basic Research Program of China (Grant Nos2010CB428602 and 2010CB428502)the National Natural Science Foundation of China (Grant No 41005023)the Program for New Century Excellent Talents in University (Grant No NCET-09-0227)
文摘Using 1958-2002 NCEPNCAR reanalysis data, we investigate stationary and transient planetary wave propagation and its role in wave-mean flow interaction which influences the state of the polar vortex （PV） in the stratosphere in Northern Hemisphere （NH） winter. This is done by analyzing the Eliassen-Palm （E-P） flux and its divergence. We find that the stationary and transient waves propagate upward and equatorward in NH winter, with stronger upward propagation of stationary waves from the troposphere to the stratosphere, and stronger equatorward propagation of transient waves from mid-latitudes to the subtropics in the troposphere. Stationary waves exhibit more upward propagation in the polar stratosphere during the weak polar vortex regime （WVR） than during the strong polar vortex regime （SVR）. On the other hand, transient waves have more upward propagation during SVR than during WVR in the subpolar stratosphere, with a domain of low frequency waves. With different paths of upward propagation, both stationary and transient waves contribute to the maintenance of the observed stratospheric PV regimes in NH winter.
基金jointly supported by an NSFC project (Grant Nos.41505034,41630423)the China National 973 project (Grant No.2015CB453200)+8 种基金NSF (AGS1565653)NSFC project (Grant No.41475084)NRL (Grant No.N00173-161G906)Jiangsu NSF key project (Grant No.BK20150062)the Startup Foundation for Introducing Talent of NUIST (Grant No.2014R010)a project funded by the Jiangsu Shuang-Chuang Team (Grant No.R2014SCT001)the Startup Foundation for Introducing Talent of NUIST (Grant No.2014R010)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe China Scholarship Council for funding and travel support
文摘The impact of La Ni?a on the winter Arctic stratosphere has thus far been an ambiguous topic of research. Contradictory results have been reported depending on the La Ni?a events considered. This study shows that this is mainly due to the decadal variation of La Ni?a’s impact on the winter Arctic stratosphere since the late 1970 s. Specifically,during the period1951–78,the tropospheric La Ni?a teleconnection exhibits a typical negative Pacific–North America pattern,which strongly inhibits the propagation of the planetary waves from the extratropical troposphere to the stratosphere,and leads to a significantly strengthened stratospheric polar vortex. In contrast,during 1979–2015,the La Ni?a teleconnection shifts eastwards,with an anomalous high concentrated in the northeastern Pacific. The destructive interference of the La Ni?a teleconnection with climatological stationary waves seen in the earlier period reduces greatly,which prevents the drastic reduction of planetary wave activities in the extratropical stratosphere. Correspondingly,the stratospheric response shows a less disturbed stratospheric polar vortex in winter.
文摘基于无线电探空仪和掩星的对流层顶观测虽然可以揭示对流层顶高度和温度的一些特性,但是在某一个地点的时间分辨率较低,资料的时间分辨率几乎都是以天计,同时所获得的对流层顶信息也不能直接反映对流层顶的产生、发展和消亡过程.借助于MST雷达具有高时间分辨率和连续性这一显著优势,实时、连续地获得对流层顶雷达回波,通过构建普适性雷达对流层顶判读模型,可以更好地研究对流层顶高度和结构形态的时空演化过程.探空仪对比实验表明:雷达方法观测对流层顶高度与气象学方法观测对流层顶高度相差约2 km,这应该和二者的探测机制相关.统计分析2012年全年雷达对流层顶回波差异值可以发现,雷达对流层顶高度的年平均值为13.3 km,标准差为0.65 km;对流层顶回波差异平均值约为11.7 d B,标准差为4.3 d B,雷达对流层顶回波差异值直接反映了雷达对流层顶结构的稀疏状态.同时本文利用Lomb-Scargle谱分析方法检测了对流层顶结构形态的扰动周期,结果表明大气潮汐波和行星波分量会影响对流层顶的结构形态.
基金supported by National Natural Science Foundation of China (Grant Nos. 40825013, 40731055, 40774085 and 40774084)the Program for Chang-jiang Scholars and Innovative Research Team in University (PCSIRT)the Open Programs of State Key Laboratory of Space Weather
文摘The characteristics of high-latitude planetary waves (PWs) in the troposphere and lower stratosphere (TLS) are studied by using the data from radiosonde observations during 1998 to 2006 at three Alaskan stations in USA (Nome, 64.50°N, 165.43°W; McGrath, 62.97°N, 155.62°W; Fairbanks, 64.82°N, 147.87°W). It is found that strong PWs exist in two regions. One is around tropopause, and the other is in the polar night jet (PNJ) in winter. The PW activities are rather intermittent, and their lifetimes are no longer than two months. Among three perturbation components in zonal and meridional winds and temperature, the temperature disturbance amplitude is the smallest, and the amplitude for the meridional wind component the largest. Around the tropopause, quasi 5-, 10-, and 16-day PW activities can be observed simultaneously. Among these PW components, the quasi 5-day and 10-day PW are the weakest and strongest, respectively. Moreover, PWs around the tropopause are complex and no obvious season variability can be observed. However, in the PNJ, the higher region, only obvious quasi 10-day and 16-day PWs remain, with smaller amplitudes than those around the tropopause. And significant PWs in the PNJ occur only in winter. By calculating the refractive index for PWs, it is found that there is a persistent reflection layer around 11 km, which is thick in summer and becomes thin or even disappears in winter, revealing that PWs in the stratosphere can only occur in winter. PWs in the 2003/2004 winter at the three stations are analyzed in detail. It is found that for the focused observation duration, the quasi 10-day and quasi 16-day waves exist mainly in the troposphere and stratosphere, respectively. The quasi 10-day wave is a standing wave in the vertical direction, with vertical wavelength about 12 km in the temperature component and larger than 26 km in the meridional component. Moreover, the tropospheric quasi 10-day wave propagates westward with the zonal numbers between 2 and 4. The quasi 16-day wave is also a stand
文摘In this paper, the variations of the mean flow, the E-P flux and its divergence of planetary waves in the process of the formation, maintenance and collapse of the blocking situation in the second half of February, 1979 are analysed with the transformed Eulerian mean-motion equations.Analysed results show that because the basic flow changes from the easterly into the westerly in the lower troposphere at high latitudes, the planetary wave for wavenumber 2 strongly propagates upwards, and because of the interaction between the upward propagating planetary wave and the basic flow, the westerty is weakened and approaches to the resonant flow of wavenumber 2 in the middle and upper troposphere (then, in the lower and middle Stratosphere). This may cause the anomalous amplification of planetary wave for wavenumber 2, and moreover make the mean flow change from the westerly into the easterly in the lower and middle stratosphere, following the upper troposphere. Therefore, the blocking situation can be formed and maintained on the Northern Hemisphere. Thus, the upward propagations of quasi-stationary planetary waves and the mutual interaction with the basic flow are also one of the reasons of the formation and maintenance of the blocking situation.
文摘A linear,hemispheric and stationary spectral model with multilayers in the vertical was employed to simulate the vertical propagation of waves triggered by mountains.Results show that,in cooperation with the East Asia zonal mean flow,Tibetan Plateau can excite a strong wavenumber 1 perturbation in the stratosphere with its ridge and trough lo- cated over the Pacific and Atlantic Oceans respectively.On the other hand,the stratospheric wavenumber 1 perturbation caused by the mechanical forcing of the Rocky Mountains in cooperation with the North America zonal mean flow is very weak.Calculations from observational data of the vertical profile of critical wavenumber for vertically propagating waves imply that the tropospheric wavenumber 1 perturbation can hardly penetrate the North America tropopause up- wards,whereas it can freely propagate through the East Asia tropopause into the stratosphere.Two-dimensional E-P cross-sections obtained from both observational data and simulated results also demonstrate that waves excited by the Rocky Mountains are refracted towards low latitudes in the troposphere during their upward propagation:whereas,in addition to the above mentioned equatorward leaning branch,the wavenumber 1 and 2 planetary waves excited by the Tibetan Plateau possess another branch which is refracted to high latitudes during upward propagation and penetrates the tropopause into the stratosphere.It is therefore concluded that the difference in the horizontal and vertical wave propagations in the two hemispheres is a result of the different dynamical forcing induced by the two main mountains in the Northern Hemisphere.
