Tropical-Dipole Mode and Its Impact on the Global Climate

Recently, the interactions between different ocean basins attract more and more attentions. Previous studies more focus on the impacts of one ocean basins (e.g. the Pacific ocean) on the other two. Many different mechanisms, including the Gill-type convection model, the stationary Rossby wave trains, the wind-evaporation-SST feedback, the Bjerknes feedback, etc, all play active roles in these interactions, making the whole process too complicated. Here we propose a new perspective of these inter-basin teleconnections, that different mechanisms between different basins may resonance with each other, forming several leading mode or processes over the entire tropical oceans.

Through spectral analysis and numerical simulations, we retrieved one of these patterns, with warming (or cooling) over the Atlantic and Indian Ocean, but La nina (El nino) type anomaly over the Pacific Ocean, which is named as the tropical – dipole pattern. This process is significant on both inter-annual and decadal time scales. The tropical -dipole patterns are usually triggered by the tropical Atlantic warming. The upper tropospheric warming, the wind-evaporation-SST feedback, the Bjerknes feedback all play important role in mediating this warming and the changes over the Indian Ocean and the Pacific. While the Pacific changes will feedback to the Atlantic and the Indian Ocean and may kill the dipole pattern or even drive it to an opposite mode.