Global Patterns of Decadal Scale Variability Observed in Sea Surface Temperature and Lower-Tropospheric Circulation Fields

Tomohiko Tomita^1,2, Bin Wang², Tetsuzo Yasunari^1,3, and

Hisashi Nakamura^1,4

1Frontier Research System for Global Change

Institute for Global Change Research

Yokohama, JAPAN

2International Pacific Research Center

University of Hawaii at Manoa

Honolulu, Hawaii, U.S.A.

3Institute of Geoscience

University of Tsukuba

Tsukuba, JAPAN

4Department of Earth and Planetary Physics

University of Tokyo

Tokyo, JAPAN

(revised to J. Geophysical Research Ocean, June 2001)

Corresponding Author Address:

Tomohiko Tomita, Ph.D.

Frontier Research System for Global Change/Institute for Global Change Research

3173-25 Showa-machi, Kanazawa-ku, Yokohama-shi, Kanagawa 236-0001, JAPAN

TEL: +81-45-778-5537 FAX: +81-45-778-5706

E-mail : tomita@jamstec.go.jp

ABSTRACT

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 midlatitude North Pacific (LNP variability), and the third extends over the North Atlantic with the decadal North Atlantic Oscillation (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.