Pacific Decadal Oscillation

Pacific Decadal Oscillation (PDO)

The Pacific decadal oscillation (PDO) is the leading pattern of decadal to multidecadal variability in North Pacific sea surface temperature (SST), excluding variability coherent with global average temperature changes. The PDO appears to be largely, though not entirely, the integrated response of the North Pacific Ocean SSTs to surface climate forcing by the El Niño–Southern Oscillation (ENSO) and from internal variability in the Aleutian low. The PDO is “ENSO-like” in the sense that the spatial structure of the PDO is well correlated with the spatial structure of ENSO variability over the North Pacific, though the PDO has noticeably more variability in the extratropical North Pacific and substantially less in the far eastern tropical Pacific.

ENSO-like SST variability on decadal and longer time scales extends to the South Pacific and to a small extent the Indian and Atlantic Oceans. This near-global pattern of variability is called the interdecadal Pacific oscillation (IPO). The spatial patterns of the PDO and IPO are similar in the North Pacific, and their time series are coherent on annual and longer time scales.

Reference

Christensen, J. H., and Coauthors, 2014: Climate phenomena and their relevance to future regional climate change. Climate Change 2013: The Physical Science Basis, T. F. Stocker et al., Eds., Cambridge University Press, 1217–1308.

term added 4 August 2014

The low pressure center located near the Aleutian Islands on mean charts of sea level pressure.
It represents one of the main centers of action in the atmospheric circulation of the Northern Hemisphere. The Aleutian low is most intense in the winter months; in summer it is displaced toward the North Pole and is almost nonexistent. On a daily basis, the area of the Aleutian low is marked by alternating high and low pressure centers, moving generally to the eastward; it is not the scene of an intense stationary low. Normally the depth of intensity of the low pressure areas exceeds the intensity of the high pressure areas, so that the region is one of low pressure on the average. The travelling cyclones of subpolar latitudes usually reach maximum intensity in the area of the Aleutian low. The Aleutian low and its counterpart in the Atlantic Ocean, the Icelandic low, compose the Northern Hemisphere's subpolar low pressure belt.