Tropical origins of North and South Pacific decadal variability

摘要

The origin of the Pacific Decadal Oscillation (PDO),the leading mode of sea surface temperature variability forthe North Pacific, is a matter of considerable debate. Oneparadigm views the PDO as an independent mode centeredin the North Pacific, while another regards it as a largelyreddened response to El Nino-Southern Oscillation (ENSO)forcing from the tropics. We calculate the SouthernHemisphere equivalent of the PDO index based on theleading mode of sea surface temperature variability for theSouth Pacific and find that it adequately explains the spatialstructure of the PDO in the North Pacific. A first-orderautoregressive model forced by ENSO is used to reproducethe observed PDO indices in the North and South Pacific.These results highlight the strong similarity in Pacificdecadal variability on either side of the equator and suggestit may best be viewed as a reddened response to ENSO. Citation: Shakun, J. D., and J. Shaman(2009), Tropical originsof North and South Pacific decadal variability.