The effects of zonally varying mean state of equatorial Pacific on planetaryequatorial trapped waves were analytically investigated. A WKB approximation was used with the slowzonal variation hypothesis, acceptable in ...The effects of zonally varying mean state of equatorial Pacific on planetaryequatorial trapped waves were analytically investigated. A WKB approximation was used with the slowzonal variation hypothesis, acceptable in the context of equatorial trapped low-frequencyvariability, and a working space transformation was made to turn the meridional trappedlow-frequency variability, and a working space transformation was made to turn the meridional modeequation into the Weber-Hermite equation in the new space. The inhomoge-neous equatorial wave ductwas proposed and the theoretical results were compared with observation. It matches the real stateof the equatorial Pacific to a certain degree.展开更多
Lateral energy exchange between the tropics and the midlatitudes is a topic of great importance for understanding Earth＇s climate system. In this paper, the authors address this issue in an idealized set up through s...Lateral energy exchange between the tropics and the midlatitudes is a topic of great importance for understanding Earth＇s climate system. In this paper, the authors address this issue in an idealized set up through simple shallow water models for the interactions between equatorially trapped waves and the barotropic mode, which supports Rossby waves that propagate poleward and can excite midlatitude teleconnection patterns. It is found here that the interactions between a Kelvin wave and a fixed meridionai shear （mimicking the jet stream） generates a non-trivial meridional velocity and meridional convergence in phase with the upward motion that can attain a maximum of about 50%, which oscillates on frequencies ranging from one day to 10 days. When, on the other hand, the barotropic flow is forced by slowly propagating Kelvin waves a complex flow pattern emerges; it consists of a phase-locked barotropic response that is equatoriaily trapped and that propagates eastward with the forcing Kelvin wave and a certain number of planetary Rossby waves that propagate westward and toward the poles as seen in nature. It is suggested here that the poleward propagating waves are to some sort of multi-way resonant interaction with the phase locked response. Moreover, it is shown here that a numerical scheme with dispersion properties that depend on the direction perpendicular to the direction of propagation, namely the 2D central scheme of Nessyahu and Tadmor, can artificially alter significantly the topology of the wave fields and thus should be avoided in climate models.展开更多
文摘The effects of zonally varying mean state of equatorial Pacific on planetaryequatorial trapped waves were analytically investigated. A WKB approximation was used with the slowzonal variation hypothesis, acceptable in the context of equatorial trapped low-frequencyvariability, and a working space transformation was made to turn the meridional trappedlow-frequency variability, and a working space transformation was made to turn the meridional modeequation into the Weber-Hermite equation in the new space. The inhomoge-neous equatorial wave ductwas proposed and the theoretical results were compared with observation. It matches the real stateof the equatorial Pacific to a certain degree.
基金Project supported in part by the Natural Sciences and Engineering Research Council of Canada (No.288339-2004)the Canadian Foundation for Climate and Atmospheric Sciences (No.GR-7021)
文摘Lateral energy exchange between the tropics and the midlatitudes is a topic of great importance for understanding Earth＇s climate system. In this paper, the authors address this issue in an idealized set up through simple shallow water models for the interactions between equatorially trapped waves and the barotropic mode, which supports Rossby waves that propagate poleward and can excite midlatitude teleconnection patterns. It is found here that the interactions between a Kelvin wave and a fixed meridionai shear （mimicking the jet stream） generates a non-trivial meridional velocity and meridional convergence in phase with the upward motion that can attain a maximum of about 50%, which oscillates on frequencies ranging from one day to 10 days. When, on the other hand, the barotropic flow is forced by slowly propagating Kelvin waves a complex flow pattern emerges; it consists of a phase-locked barotropic response that is equatoriaily trapped and that propagates eastward with the forcing Kelvin wave and a certain number of planetary Rossby waves that propagate westward and toward the poles as seen in nature. It is suggested here that the poleward propagating waves are to some sort of multi-way resonant interaction with the phase locked response. Moreover, it is shown here that a numerical scheme with dispersion properties that depend on the direction perpendicular to the direction of propagation, namely the 2D central scheme of Nessyahu and Tadmor, can artificially alter significantly the topology of the wave fields and thus should be avoided in climate models.
