强迫耗散正压大气中四波共振

Four-Wave Resonance in Driving and Dissipating Barotropic Atmosphere

本文首次研究了含Ekman摩擦和非绝热加热的四波共振动力学．使用新的双时间尺度和新的时间变换式，由四波共振的广义Landau方程，导得普遍的非线性低频周期解，Ekman摩擦使得低频周期具有滞后和突变返回两个重要特征，而非绝热加热作用与中高纬准双周振荡有关，中高纬的30－50天振荡则与自由Rossby波准共振有关．本文还研究了四波共振产生的爆发性不稳定，指出较大振幅波产生的爆发性不稳定可能是阻塞迅速形成的又一重要原因，还首次得到在正压大气中Ekman摩擦能够激发爆发性不稳定．本文结果纠正了Craik于1985年提出的在流体力学中广泛应用的两个错误论断．

Four-wave resonance dynamics including Ekman friction and diabatic heating is studiedfirst time in this paper.By using two new time scales and new time transformation forlnula, thegeneral nonlinear periodic solution of the low-frequency is obtained from the general Landauequations for resonance of four- wave. Ekman friction leads the low- frequency period to havetwo important characteristics i. e. hysteresis and catastrophic return, while effect of diabaticheating has relation to quasi - two week oscillation in the mid - high latitude; but 30- 50 dayoscillation in the mid-high latitude has relation to quasi-resonance of free Rossby waves.Theexplosive instability caused by the four-wave resonance is also studied, it is pointed out thatthe explosive. instability formed by waves of larger amplitude may be another important reasonwhy the blocking forms rapidly. It is found that in the barotropic atmosphere Ekman frictioncan excite the explosive instability. The results of this paper correct two error assertions usedwidely in the fluid dynamics proposed by Craik in 1985.