Influences of basic flow on unstable excitation of intraseasonal oscillation in mid-high latitudes

【摘要】 <正> The influences of basic flow fields on the unstable excitation of the intraseasonal atmosphericoscillation in the mid-high latitudes are studied by using a simple nonlinear dynamical model.The results showthat the westerly profile has an important effect on unstable modes in the atmosphere;the growth rates andspectrum distributions of the excited unstable modes are different for the different profiles.For the usualwesterly profile patterns in the real atmosphere,the most unstable mode is in the intraseasonal(30—60 d)frequency band.The local intensity and meridional gradient of the westerlies also clearly affect unstablemodes.The consistency of the results in observational data analyses with that in dynamical theory proved thecorrectness and rationalization of the above-mentioned results.更多还原

【Abstract】 The influences of basic flow fields on the unstable excitation of the intraseasonal atmospheric oscillation in the mid-high latitudes are studied by using a simple nonlinear dynamical model.The results show that the westerly profile has an important effect on unstable modes in the atmosphere;the growth rates and spectrum distributions of the excited unstable modes are different for the different profiles.For the usual westerly profile patterns in the real atmosphere,the most unstable mode is in the intraseasonal(30—60 d) frequency band.The local intensity and meridional gradient of the westerlies also clearly affect unstable modes.The consistency of the results in observational data analyses with that in dynamical theory proved the correctness and rationalization of the above-mentioned results.更多还原