Seasonal and Interannual Variabilities of the Pacific Ocean Circulation and Their Relevance to ENSO

本文利用高分辨率大气环流模式（GCM）研究了太平洋海洋环流在理想地表热通量条件下的时空变化。以下是数值模拟的主要结论。(1)具有气旋环流特征的哥斯达黎加圆顶在春末快速增长，夏秋初秋成熟，与ITCZ向北迁移一致。在冬季，强大的北方辐合最南端的南太平洋区域激发温暖的反气旋暖涡流，侵蚀哥斯达黎加圆顶。只有在冬季和早春，气旋涡旋的胚胎得到预先准备，哥斯达黎加圆顶才能在夏季由气旋旋度的风维持。(2)棉兰老岛巨蛋在菲律宾海岸晚秋形成，这是由于局地上升流的影响，与东北亚冬季风相关的正旋度在该地区增加。冬季达到最大值后，春季开始衰减，主要是由于冬季东北信风在160 -E附近激发的长罗斯比下潜波侵入，以及局地正风应力旋度的消退。棉兰老岛圆丘模式的季节变化几乎完全取决于日期变更线以西西太平洋风场的变化。

We have investigated temporal and spatial variabilities of the ocean circulation in the Pacific using a high resolution general circulation model (GCM) forced by the observed winds with idealized surface heat fluxes. The following are major conclusions from the numerical simulations.(1) The Costa Rica Dome with a cyclonic circulation grows rapidly in late spring and matures in summer and early fall in accord with the northward migration of the ITCZ. In winter strong northerns converging the southernmost ITCZ excite warm anticyclonic warm eddies, which erode the Costa Rica Dome. The Costa Rica Dome can be maintained by the winds with the cyclonic curl in summer only when the embryo of a cyclonic eddy is preconditioned in winter and early spring.(2) The Mindanao Dome evolves in late fall off the Philippine coast due to local upwellinhs when a positive curl associated witn the northeast Asian winter monsoon increases over the region. After reaching a maximum in winter it begins to decay in spring due to an intrusion of downwelling long Rossby waves excited in winter by the northeast trade winds farther eastward near 160 -E, as well as a retreat of the local positive wind stress curl. The seasonal variation of the model Mindanao Dome is almost perfectly determined by the change of the wind field in the western Pacific west of the date line.