Here is another view of the SOI dipole. The way to read this is that when the atmospheric pressure at Darwin is low then it is high at Tahiti (and vice versa). So this contour plot is essentially a series of 1D cross-sections as the pressure varies from west (Darwin) to east (Tahiti) with time increasing downward. The model is on the left and the somewhat noisy data on the right.

![SOI dipole](