【摘要】 用数值方法研究了自由模对强迫耗散系统解的轨线的影响。首先,用变分法得到实际大气自由模,并设计一族解析自由模—理想大气自由模;其次,以两类自由模分别作强迫场,初始场取1993年7月1日的500hPa流函数场,然后应用强迫耗散正压涡度方程的全球谱模式积分300d,得到:(1)以1992年12月27—28日500hPa的实际大气自由模作强迫场时,1α=γ=κ≥0.02,强迫、耗散系数相等且足够大时,随着时间演变,大气总是接近自由模态;2强迫系数α=0.1,耗散系数γ=0.02时,中高纬出现局地性准双周振荡。(2)以理想大气自由模作强迫场时,固定耗散系数γ=0.01,强迫系数0.0095≤α≤0.011时,振荡周期与强迫系数呈正相关关系。更多还原

【Abstract】 The effect of the free mode on the trajectory of the solutions to a forced dissipative system is numerically researched.First,the free mode is obtained from observed atmosphere and a type of analytical free mode(ideal free mode) is designed;Secondly,using two kinds of the free modes as forcing fields respectively,and the 500hPa streamfunction field for July 1,1993 as the initial field, then the numerical experiments are run for 300 days by a forcing and dissipative global spectral model.Results indicate that when using the observed free mode for December 27-28,1992 as the forcing field,and α=γ=κ≥0.02,that is to say,when the forcing and dissipative coefficient is equivalent and great enough,the model atmosphere always approaches to the free mode as time evolves;when the forcing coefficient α=0.1 and the dissipative coefficient γ=0.02,the local quasi-biweekly oscillation appears in the extratropical latitude.When using the free mode of idealized atmosphere,dissipative coefficient 0.01,and forcing coefficient 0.0095≤α≤0.011, the period of oscillation has a positive correlation with the amplitude of the forcing coefficient.更多还原