海洋中长生命反气旋涡在地形上的演变以及涡旋的合并现象

THE EVOLUTION OF LONG-LIVED ANTICYCLONIC VORTICES OVER TOPOGRAPHY IN AN OCEAN AND THEIR MERGING

通过对海洋中长生命反气旋涡在Gauss型孤立地形上演变的研究 ,发现地形对长生命反气旋涡的发展和传播有相当重要的影响。在无地形作用的情况下 ,仅有反气旋涡能够存在于向西的均匀基流中 ,这个涡是长生命的 ,并且在西移过程中有明显的向西倾斜。然而当其上游存在一个孤立地形时 ,可以发现这个涡有一个向东的倾斜 ,它的强度将增强且向西的移速会增加 ,其规迹象陀螺的运动。另一方面 ,当两个强度相同的反气旋涡同时存在时 ,这两个涡并不合并 ,且能持续很长的时间。当这两个涡的上游存在一个孤立地形时 ,这两个涡可以产生合并 ,并形成一个强度相当大的涡。

In this paper, the evolution of long-lived anticyclonic vortices over a Gaussian-shape topography is investigated. It is found that the Gaussian-shape topography has an important influence on the evolution of the long-lived anticyclonic vortices. Under the condition that there is no topographic forcing, only anticyclonic vortices can exist in the uniform westward basic flow. These vortices are long-lived and have a westward tilt. However, if a Gaussian-shape topography exists in the upstream of an anticyclonic vortex, then the vortex will be strengthened and its westward speed increases. Its trajectory looks like the motion of a top. On the other hand, when two anticyclonic vortices having an identical amplitude exist in a uniform westward basic flow, the two vortices do not merge if the topography does not exist. However, once a Gaussian-shape topography exists in the upstream of the two vortices, they can merge and develop into a strong anticyclonic vortex.