Atmospheric response to the South Pacific Subtropical Dipole

Recent studies have suggested a dipolar mode of sea surface temperature variability in the subtropical South Pacific that matures in the austral summer, which is known as the South Pacific Subtropical Dipole (SPSD). In our study, the summer atmospheric response to the SPSD is investigated using observational data and numerical model experiments. Our results show a baroclinic response equatorward of 30 degrees S and a barotropic response poleward of 30 degrees S. The SPSD causes precipitation anomalies over the subtropical South Pacific, and the associated diabatic heating induces a baroclinic response. The mid- and high-latitude barotropic response is similar to the Southern Annual Mode (SAM) and is accompanied by an anomalous shift of storm tracks. The associated anomalous eddy activity is responsible for the SAM-like response. The results of numerical model experiments are consistent with our observations, except for the weak response in the high latitude. In the subtropical South Pacific, the spatial pattern of atmospheric response to the SPSD resembles the atmospheric anomalies that force the SPSD. The subtropical atmospheric response and the SPSD interact with each other and comprise a coupled system.