The structure of planetary scale low freonency phenomena in the tropics is studied, and an attempt is made to determine its influence and interactions with phenomena at higher latitudes.In the tropics, it is found tha...The structure of planetary scale low freonency phenomena in the tropics is studied, and an attempt is made to determine its influence and interactions with phenomena at higher latitudes.In the tropics, it is found that the majority of the variance in the zonal wind structure is made up in wave numbers I and 2. During warm events in the Pacific Ocean, when the Southern Oscillation Index is negative, almost all of the variance resides in the gravest mode which undergoes a 40° eastward phase shift. Meanwhile, the second logitudinal mode almost disappears. On the other hand, the meridional wind field possesses maximum amplitude at higher wave numbers. However, near the equator,the amplitude is small with extreme values occurring in the subtropics. The difference in scale and the location of cxtrcma of the meridional and zonal wind components indicate that the tropical atmosphere is responding to two different driving mechanisms.Correlation analyses between variations of the zonal wind at reference points along the equator with variations of component elsewhere show that there are strong logitudinal connections. The strongest correlations between the tropics and higher latitudes exist in the region of the equatorial westerlies. In fact, stronger correlations occur between variations in U anywhere along the equator and the middle latitudes to the north and south of the equatorial westerlies than to the latitudes immediately to the north and south of the reference points. We interpret this 'remote' correlation pattern as indicating a two-stage teleconnection process which emphasizes the importance of the equatorial tropical westerlies of the Pacific Ocean as a 'corridor' of communication between the low and high latitudes. The regionality of the correlations confirms, to some extent, recent theoretical development regarding trapped equatorial modes. Finally, time lagged correlations from plus and minus six months between variations of U and OLR indicate that the interactions between the extratropics and low latitudes possess an organized sequence. The extratropical influence appears to propagate into the tropics followed by an eastward propagation along the equator. Finally, a propagation from the tropics to the extratropics in the upper troposphere occurs in the eastern Pacific Ocean. The time-lagged correlation sequence does not appear to be symmetric about the equator.展开更多
A fluid-structure interaction system subject to Sommerfeld＇s condition is defined as a Sommerfeld system which is divided into three categories： Fluid Sommerfeld （FS） System, Solid Sommerfeld （SS） System and Flu...A fluid-structure interaction system subject to Sommerfeld＇s condition is defined as a Sommerfeld system which is divided into three categories： Fluid Sommerfeld （FS） System, Solid Sommerfeld （SS） System and Fluid Solid Sommerfeld （FSS） System of which Sommerfeld conditions are imposed on a fluid boundary only, a solid boundary only and both fluid and solid boundaries, respectively. This paper follows the previous initial results claimed by simple examples to further mathematically investigate the natural vibrations of generalized Sommerfeld systems. A new parameter representing the speed of radiation wave for generalized 3-D problems with more complicated boundary conditions is introduced into the Sommerfeld condition which allows investigation of the natural vibrations of a Sommerfeld system involving both free surface and compressible waves. The mathematical demonstrations and selected examples confirm and reveal the natural behaviour of generalized Sommerfeld systems defined above. These generalized conclusions can be used in theoretical or engineering analysis of the vibrations of various Sommerfeld systems in engineering.展开更多
Within the framework of forcing/dissipation KDV dynamics, the effect is numerically studied of successive east-travelling troughs on quasi-stationary high's ridges downstream. Results show that two types of low-fr...Within the framework of forcing/dissipation KDV dynamics, the effect is numerically studied of successive east-travelling troughs on quasi-stationary high's ridges downstream. Results show that two types of low-fre- quency transiency are available, depending on the intensities of down-drifting troughs. One is that transiency occurs in strength, i.e., the ridge undergoes transient change in intensity with unchanged position; the other is that transiency takes place in pattern, viz., the breakdown of the quasi-stationary character of the ridge's posi- tion, meaning that the ridge is replaced by a trough, followed by multiple transformation between ridge and trough.展开更多
3 Summary and discussion In the generalized drift resonance theory[17],a characteristic signature of the ULF wave-particle interactions is the increasingly-tilted stripes in the particle energy spectrum.The phase diff...3 Summary and discussion In the generalized drift resonance theory[17],a characteristic signature of the ULF wave-particle interactions is the increasingly-tilted stripes in the particle energy spectrum.The phase difference across different energy channels is relatively small展开更多
The nonlinear interactions between river discharge,astronomical tidal wave,and local geomorphology during storm passage or water release from upstream dams can produce severe floods in the Río Negro lower basin(A...The nonlinear interactions between river discharge,astronomical tidal wave,and local geomorphology during storm passage or water release from upstream dams can produce severe floods in the Río Negro lower basin(Argentina).For this reason,this paper aims to detect and study nonlinear processes in this area.The watercourse hydrodynam-ics was described using hourly water level data from three limnigraphs during 2003–2021 and flow time series.The tide gauge dataset was employed to describe the influence of tidal cycles on the hydrological regimen.Nonlinear processes’impact on the astronomical tidal cycle and river discharge was analyzed using Harmonic Analysis,and Fou-rier higher-order spectra,also it was complemented with the selection of two study cases.Harmonic Analysis results showed that the tidal wave entry upstream of the Río Negro modulates its hydrological regime,presenting the water column semidiurnal variations.Also,high-order spectral analysis detected nonlinear interactions in the signal in storm conditions with an energetic redistribution among the linear tidal constituents toward shallow water harmonics.Additionally,nonlinear interactions provoked a delay in the tidal ebb phase with a consequential extension of flood-ing duration time.This type of study contributes to the knowledge of the flood mechanisms activated during a storm.展开更多
文摘The structure of planetary scale low freonency phenomena in the tropics is studied, and an attempt is made to determine its influence and interactions with phenomena at higher latitudes.In the tropics, it is found that the majority of the variance in the zonal wind structure is made up in wave numbers I and 2. During warm events in the Pacific Ocean, when the Southern Oscillation Index is negative, almost all of the variance resides in the gravest mode which undergoes a 40° eastward phase shift. Meanwhile, the second logitudinal mode almost disappears. On the other hand, the meridional wind field possesses maximum amplitude at higher wave numbers. However, near the equator,the amplitude is small with extreme values occurring in the subtropics. The difference in scale and the location of cxtrcma of the meridional and zonal wind components indicate that the tropical atmosphere is responding to two different driving mechanisms.Correlation analyses between variations of the zonal wind at reference points along the equator with variations of component elsewhere show that there are strong logitudinal connections. The strongest correlations between the tropics and higher latitudes exist in the region of the equatorial westerlies. In fact, stronger correlations occur between variations in U anywhere along the equator and the middle latitudes to the north and south of the equatorial westerlies than to the latitudes immediately to the north and south of the reference points. We interpret this 'remote' correlation pattern as indicating a two-stage teleconnection process which emphasizes the importance of the equatorial tropical westerlies of the Pacific Ocean as a 'corridor' of communication between the low and high latitudes. The regionality of the correlations confirms, to some extent, recent theoretical development regarding trapped equatorial modes. Finally, time lagged correlations from plus and minus six months between variations of U and OLR indicate that the interactions between the extratropics and low latitudes possess an organized sequence. The extratropical influence appears to propagate into the tropics followed by an eastward propagation along the equator. Finally, a propagation from the tropics to the extratropics in the upper troposphere occurs in the eastern Pacific Ocean. The time-lagged correlation sequence does not appear to be symmetric about the equator.
文摘A fluid-structure interaction system subject to Sommerfeld＇s condition is defined as a Sommerfeld system which is divided into three categories： Fluid Sommerfeld （FS） System, Solid Sommerfeld （SS） System and Fluid Solid Sommerfeld （FSS） System of which Sommerfeld conditions are imposed on a fluid boundary only, a solid boundary only and both fluid and solid boundaries, respectively. This paper follows the previous initial results claimed by simple examples to further mathematically investigate the natural vibrations of generalized Sommerfeld systems. A new parameter representing the speed of radiation wave for generalized 3-D problems with more complicated boundary conditions is introduced into the Sommerfeld condition which allows investigation of the natural vibrations of a Sommerfeld system involving both free surface and compressible waves. The mathematical demonstrations and selected examples confirm and reveal the natural behaviour of generalized Sommerfeld systems defined above. These generalized conclusions can be used in theoretical or engineering analysis of the vibrations of various Sommerfeld systems in engineering.
基金This work is supported in part by National Natural Science Foundation of Chinain part by the State Meteorological Adiministration Climate Research Funds.
文摘Within the framework of forcing/dissipation KDV dynamics, the effect is numerically studied of successive east-travelling troughs on quasi-stationary high's ridges downstream. Results show that two types of low-fre- quency transiency are available, depending on the intensities of down-drifting troughs. One is that transiency occurs in strength, i.e., the ridge undergoes transient change in intensity with unchanged position; the other is that transiency takes place in pattern, viz., the breakdown of the quasi-stationary character of the ridge's posi- tion, meaning that the ridge is replaced by a trough, followed by multiple transformation between ridge and trough.
基金supported by the National Natural Science Foundation of China(Grant Nos.41421003&41474140)
文摘3 Summary and discussion In the generalized drift resonance theory[17],a characteristic signature of the ULF wave-particle interactions is the increasingly-tilted stripes in the particle energy spectrum.The phase difference across different energy channels is relatively small
文摘The nonlinear interactions between river discharge,astronomical tidal wave,and local geomorphology during storm passage or water release from upstream dams can produce severe floods in the Río Negro lower basin(Argentina).For this reason,this paper aims to detect and study nonlinear processes in this area.The watercourse hydrodynam-ics was described using hourly water level data from three limnigraphs during 2003–2021 and flow time series.The tide gauge dataset was employed to describe the influence of tidal cycles on the hydrological regimen.Nonlinear processes’impact on the astronomical tidal cycle and river discharge was analyzed using Harmonic Analysis,and Fou-rier higher-order spectra,also it was complemented with the selection of two study cases.Harmonic Analysis results showed that the tidal wave entry upstream of the Río Negro modulates its hydrological regime,presenting the water column semidiurnal variations.Also,high-order spectral analysis detected nonlinear interactions in the signal in storm conditions with an energetic redistribution among the linear tidal constituents toward shallow water harmonics.Additionally,nonlinear interactions provoked a delay in the tidal ebb phase with a consequential extension of flood-ing duration time.This type of study contributes to the knowledge of the flood mechanisms activated during a storm.
