Global patterns of decadal-scale variability observed in sea surface temperature and lower-tropospheric circulation fields

The global patterns associated with decadal-scale variability (DSV) are examined by a lag correlation technique based on local anomaly indices, using the fields of measured sea surface temperature (SST) and 850 hPa geopotential height for the last 50 years. The three dominant patterns are identified, and the variability is examined; the first spreads over the entire Pacific, which is concurrent with the decadal-scale modulation of the El Niño/Southern Oscillation (DES variability), the second is confined to the local midlatitude North Pacific (LNP variability), and the third extends over the North Atlantic with the decadal North Atlantic Oscillation (NAO) (DNA variability). The global SST pattern of DES variability exhibits large-scale equatorial symmetry in the Pacific, which is similar to that of the Pacific Decadal Oscillation but is distinguished by the signals in the subtropical frontal zones. These SST anomalies are accompanied by anomalous subtropical highs that appear prior to the anomalous depression around Australia. The LNP variability, which is related with the Arctic Oscillation, is characterized by the SST anomalies along the North Pacific subarctic frontal zone moving eastward accompanied by the anomalous Aleutian Low. This variability develops (decays) without (with) coherent variability in the tropics. It shows the 6-year quadrature phase relationship with the DES variability, indicative of an interdecadal variability with a period of 24 years. The DNA variability is featured by the atmospheric NAO and by the SST anomalies in four zonal bands that spread in the North Atlantic from the tropics to high latitudes. This variability is independent of either the DES or LNP variability.