中尺度涡旋影响吕宋海峡黑潮变异的动力机制

Dynamics of eddy-induced Kuroshio variability in Luzon Strait

使用1.5层约化重力准地转模式,研究了西边界流在西边界缺口处当处于迟滞过程的临界状态时,其路径转变受中尺度涡旋影响的动力机制,初步探讨了中尺度涡旋影响西边界流在缺口处路径变化的几种形式。结果表明,气旋和反气旋中尺度涡旋都可能使西边界流产生由入侵流态到跨隙流态的转变,而只有反气旋式中尺度涡才有可能诱发西边界流由跨隙流态向入侵流态的转变。当西边界流远离其临界状态时,其路径不容易受中尺度涡旋的影响,此时跨隙的西边界流会阻挡中尺度涡旋在缺口处的向西传播,并迫使涡旋在吕宋海峡东侧向北移动。以上结果用来解释了吕宋海峡黑潮变异的某些结构特征。

The dynamics of eddy-induced Kuroshio variability in the Luzon Strait are studied using a 1.5- layer reduced-gravity quasi-geostrophic model. The model experiments suggest that, when the Kuroshio is close to the critical states of hysteresis, both cyclonic and anti-cyclonic mesoscale eddies can induce transition of the Kuroshio path from an anti-cyclonic intrusion to a gap-leaping state in the Luzon Strait, whereas only cyclonic eddies can force the Kuroshio from the leaping path to an penetrating path. The dynamics of the path transition is related to the hysteresis of the Kuroshio in the Luzon Strait, whereby multiple steady states exist in the nonlinear system so that the path of the Kuroshio cannot returned to its initial state after the external force is removed. When the Kuroshio is far away from the critical states of hysteresis, its path is not sensitive to eddy perturbation. In this case, the gap-leaping Kuroshio blocks the westward propagation of meso-scale eddies in the Luzon Strait and pushes the eddies to migrate northward along the eastern side of the Luzon Strait.