In this paper, the nonlinear Kelvin wave equations with 'positive-only' nonlinear (conditional) heating at the equator are reduced to a sixth-order nonlinear ordinary differential equation by using the Galerki...In this paper, the nonlinear Kelvin wave equations with 'positive-only' nonlinear (conditional) heating at the equator are reduced to a sixth-order nonlinear ordinary differential equation by using the Galerkin spectral truncated method. The stability analysis indicates that when the heating parameter increases, the supercritical pitchfork and Hopf bifurcations can occur for the prescribed three heating profiles. Numerical calculations are made with the help of the fourth-order Rung-Kutta method. It is found that the convection heating-related Hopf bifurcation can lead to limit cycle and chaotic solutions. In a wide range of heating parameter, the solutions possess 30-60-day periods, and are dominated by wavenumbers one and two, especially by wavenumber-one. In addition, the zonal winds of the low-frequency solutions have a phase reversal between the upper and lower tropospheres. Thus, it appears that the convection heating-related Hopf bifurcation might be a possible mechanism of 30-60-day oscillation in the tropical atmosphere.展开更多
The 30-60 day oscillation is an important aspect of the atmospheric variance in the tropical area. A number of works have been done on this phenomenon, this article is a further one. A quasi-geostrophic linear model t...The 30-60 day oscillation is an important aspect of the atmospheric variance in the tropical area. A number of works have been done on this phenomenon, this article is a further one. A quasi-geostrophic linear model that consists of a two-layer free atmosphere and a well-mixed boundary layer is used to investigate the instability of intraseasonal oscillation, its propagation and vertical structures. Results show that the dynamical coupling and interaction between the barotropic and baroclinic components via boundary layer convergence / divergence are responsible for the appearance of a new kind of low-frequency wave. Such wave is very different from the traditional tropical Rossby wave. It can propagate westward and eastward. Some behaviours of it appear to resemble the observed 30-60 day oscillation mode in many aspects, such,as vertical structures, zonal and meridional propagations. Now many researchers emphasize the direct relationship between CISK-Kelvin mode and the tropical atmospheric 30-60 oscillation. It is considered that CISK-Rossby mode should not be neglected.展开更多
Dynamic study is undertaken of the tropical atmospheric CISK-Rossby wave genesis and propagation mechanisms, the vertical structure of the low-frequency wave and the basic characteristics and constraint of the vertica...Dynamic study is undertaken of the tropical atmospheric CISK-Rossby wave genesis and propagation mechanisms, the vertical structure of the low-frequency wave and the basic characteristics and constraint of the vertical transport of momentum and wave energy fluxes in relation to the quasi-biennial oscillation (QBO) of the stratospheric zonal winds over the tropics in the context of a baroclinic quasi-geostrophic model. Results suggest that in the properly posed thermal conditions and zonal belt there exist two kinds of CISK-Rossby waves of low frequency (LF) and very low frequency (VLF), travelling zonally in opposite directions, which act as sources responsible for upward transferring momentum and wave energy fluxes for easterly and westerly perturbations in such a way as to provide required momentum and energy for the stratospheric QBO genesis and maintenance. The present study offers interpretations for some of the fundamental observational facts of the QBO and proposes new ideas of the QBO generation mechanism.展开更多
To add to the growing mature research on the tropical 30-50 day oscillations from a new prospective, the current work bases on dynamic analysis of baroclinic quasi-geostrophic models to discuss dynamic mechanisms for ...To add to the growing mature research on the tropical 30-50 day oscillations from a new prospective, the current work bases on dynamic analysis of baroclinic quasi-geostrophic models to discuss dynamic mechanisms for the generation and propagation of CISK-Rossby waves, and to understand restraints and effects of different wave structures and thermodynamic forcing on the 30-50 day oscillations in the tropical atmosphere. Some important properties of the oscillation propagation have been explained and, in detail, with respect to its meridional propagation and vertical "baroclinic" structure. The work has come up with some new opinions and viewpoints. New opinions about the propagation and energy dispersion are to be proved by more observations and study.展开更多
文摘In this paper, the nonlinear Kelvin wave equations with 'positive-only' nonlinear (conditional) heating at the equator are reduced to a sixth-order nonlinear ordinary differential equation by using the Galerkin spectral truncated method. The stability analysis indicates that when the heating parameter increases, the supercritical pitchfork and Hopf bifurcations can occur for the prescribed three heating profiles. Numerical calculations are made with the help of the fourth-order Rung-Kutta method. It is found that the convection heating-related Hopf bifurcation can lead to limit cycle and chaotic solutions. In a wide range of heating parameter, the solutions possess 30-60-day periods, and are dominated by wavenumbers one and two, especially by wavenumber-one. In addition, the zonal winds of the low-frequency solutions have a phase reversal between the upper and lower tropospheres. Thus, it appears that the convection heating-related Hopf bifurcation might be a possible mechanism of 30-60-day oscillation in the tropical atmosphere.
文摘The 30-60 day oscillation is an important aspect of the atmospheric variance in the tropical area. A number of works have been done on this phenomenon, this article is a further one. A quasi-geostrophic linear model that consists of a two-layer free atmosphere and a well-mixed boundary layer is used to investigate the instability of intraseasonal oscillation, its propagation and vertical structures. Results show that the dynamical coupling and interaction between the barotropic and baroclinic components via boundary layer convergence / divergence are responsible for the appearance of a new kind of low-frequency wave. Such wave is very different from the traditional tropical Rossby wave. It can propagate westward and eastward. Some behaviours of it appear to resemble the observed 30-60 day oscillation mode in many aspects, such,as vertical structures, zonal and meridional propagations. Now many researchers emphasize the direct relationship between CISK-Kelvin mode and the tropical atmospheric 30-60 oscillation. It is considered that CISK-Rossby mode should not be neglected.
基金the National Natural Sciences Foundation of China!49975012 the Program of Basic Theoretical Research of the PLA Headquart
文摘Dynamic study is undertaken of the tropical atmospheric CISK-Rossby wave genesis and propagation mechanisms, the vertical structure of the low-frequency wave and the basic characteristics and constraint of the vertical transport of momentum and wave energy fluxes in relation to the quasi-biennial oscillation (QBO) of the stratospheric zonal winds over the tropics in the context of a baroclinic quasi-geostrophic model. Results suggest that in the properly posed thermal conditions and zonal belt there exist two kinds of CISK-Rossby waves of low frequency (LF) and very low frequency (VLF), travelling zonally in opposite directions, which act as sources responsible for upward transferring momentum and wave energy fluxes for easterly and westerly perturbations in such a way as to provide required momentum and energy for the stratospheric QBO genesis and maintenance. The present study offers interpretations for some of the fundamental observational facts of the QBO and proposes new ideas of the QBO generation mechanism.
基金Natural Science Foundation of China (49975012) Key Teacher Foundation of Education Ministry
文摘To add to the growing mature research on the tropical 30-50 day oscillations from a new prospective, the current work bases on dynamic analysis of baroclinic quasi-geostrophic models to discuss dynamic mechanisms for the generation and propagation of CISK-Rossby waves, and to understand restraints and effects of different wave structures and thermodynamic forcing on the 30-50 day oscillations in the tropical atmosphere. Some important properties of the oscillation propagation have been explained and, in detail, with respect to its meridional propagation and vertical "baroclinic" structure. The work has come up with some new opinions and viewpoints. New opinions about the propagation and energy dispersion are to be proved by more observations and study.
