A monopolar vortex encounters an isolated topographic feature on a beta-plane

J.H.G.M. van Geffen and P.A. Davies
Dynam. Atmosph. & Oceans 32, 1--26 (2000)


A two-dimensional numerical model is used to investigate the possible effects of a cosine-shaped, circularly-symmetric seamount on the motion of a monopolar vortex on a beta-plane. The monopole moves to the north-west due to the beta-effect and encounters the seamount from the south-east. The lateral dimension of the topographic feature is varied between one and four times that of the monopole and the seamount is located at latitudes between far south and far north of the equator. For comparable topographic and vortex scales, the monopole's trajectory differs somewhat from its trajectory in the absence of any bottom topography, the difference being bigger for mountains further away from the equator. Large seamounts in the southern hemisphere can deflect the monopole more towards the north or they can rebound the monopole back to the south-east, thus forming a barrier for the vortex. Large seamounts in the northern hemisphere deform the monopole significantly, leading to complicated trajectories after the vortex has crossed the topography, or to trapping (permanently or temporarily) by the topography. If it is trapped, the monopole circles around the top of the mountain, while performing small loops, and it is eventually destroyed by the topography-induced vorticity.


   1. Introduction
   2. Description of the model
      2.1 The numerical method
      2.2 The monopole and the seamount
      2.3 Review of the main model assumptions
   3. Results of the interaction simulations
      3.1 The parameters in the simulation
      3.2 A seamount at the equator and to the south, respectively  
          ===>  Web pages:  at equator / at southern hemisphere
      3.3 A small seamount north of the equator
      3.4 A large seamount north of the equator
          ===>  Web pages:  at northern hemisphere
   4. Concluding remarks

Full paper (1.9MB)

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