(1 ) Assuming that there is a zero-divergent layer in mid-troposphere, a diabatic and quasi-geostrophic equation set (bearing the format of that for barotropic vorticity) is derived by vertical integration of the ther...(1 ) Assuming that there is a zero-divergent layer in mid-troposphere, a diabatic and quasi-geostrophic equation set (bearing the format of that for barotropic vorticity) is derived by vertical integration of the thermodynamics equation and approximate description of anomalous tropospheric heating field in a simultaneous equation.(2) Discussing the spectral mean and group velocities, it is proved that the enclosed centers of the climatically mean geopotential field are no other than the atmospheric low-frequency oscillators ill the mid- and higher- latitudes. They have reversed variation of phase on two sides, with the energy supplied by the positive feedback of condensation by CISK or the sensible heat of sea temperature. (3) A formula is derived for low-frequency teleconnecting rays, which are shown to cross the streamlines southward in the northerly or northward in the southerly and to change direction of movement at the bottom of troughs or the top of ridges. Comparing to the great circle argument. the theoretic results above are more reasonable in explaining the observed low-frequency teleconnection in the Northern Hemisphere.展开更多
In consideration of the characteristics of spectral average of the Rossby wave trains and the adoption of a climatic mean stream field as the basic stream field, an approximate analytical formula for the period of atm...In consideration of the characteristics of spectral average of the Rossby wave trains and the adoption of a climatic mean stream field as the basic stream field, an approximate analytical formula for the period of atmospheric low-frequency oscillation (LFO) and the group velocity is deduced from a barotropic and non-divergent linearized vorticity equation. All the action centers of atmosphere are found to be the oscillators of low frequency. The LFO propagates southward across the streamlines in the wind field with a southward component or propagates northward across the streamlines in the wind field with northward component instead of along a great circle. The switch of the propagation direction takes place near the top of ridge or the bottom of trough. The angle between the wave rays and the zonal direction can be determined.展开更多
文摘(1 ) Assuming that there is a zero-divergent layer in mid-troposphere, a diabatic and quasi-geostrophic equation set (bearing the format of that for barotropic vorticity) is derived by vertical integration of the thermodynamics equation and approximate description of anomalous tropospheric heating field in a simultaneous equation.(2) Discussing the spectral mean and group velocities, it is proved that the enclosed centers of the climatically mean geopotential field are no other than the atmospheric low-frequency oscillators ill the mid- and higher- latitudes. They have reversed variation of phase on two sides, with the energy supplied by the positive feedback of condensation by CISK or the sensible heat of sea temperature. (3) A formula is derived for low-frequency teleconnecting rays, which are shown to cross the streamlines southward in the northerly or northward in the southerly and to change direction of movement at the bottom of troughs or the top of ridges. Comparing to the great circle argument. the theoretic results above are more reasonable in explaining the observed low-frequency teleconnection in the Northern Hemisphere.
文摘In consideration of the characteristics of spectral average of the Rossby wave trains and the adoption of a climatic mean stream field as the basic stream field, an approximate analytical formula for the period of atmospheric low-frequency oscillation (LFO) and the group velocity is deduced from a barotropic and non-divergent linearized vorticity equation. All the action centers of atmosphere are found to be the oscillators of low frequency. The LFO propagates southward across the streamlines in the wind field with a southward component or propagates northward across the streamlines in the wind field with northward component instead of along a great circle. The switch of the propagation direction takes place near the top of ridge or the bottom of trough. The angle between the wave rays and the zonal direction can be determined.
