Uncertainty in Pacific Decadal Oscillation index

Caihong Wen1, Arun Kumar2 and Yan Xue2, (1)NOAA/CPC college park, College Park, MD, United States, (2)NOAA/NCEP, Climate Prediction Center, College Park, MD, United States
Abstract:
Pacific Decadal Oscillation (PDO) index is an important indicator of climate variability. However,

large discrepancies are found among real-time PDO monitoring indices maintained by several operational

centers, with larger uncertainty exhibiting prior to 1950s and after late 1990s on seasonal to decadal

time scales. We used two historical sea surface temperature (SST) data sets to investigate causes for the

uncertainty: the Extended Reconstructed Sea Surface Temperature version 3b (ERSST 3b) and the Hadley

Center Sea Ice and SST data set (HadISST) version 1. It is found that choices of spatial structure of Empirical

Orthogonal Function (EOF) vector and SST data set are important sources of uncertainty on seasonal to

decadal time scales, while choice of climatological base period only contributes to uncertainty on seasonal

time scale. Decadal variation of differences in PDO indices from ERSST and HadISST is associated with

systematic differences between the two data sets in the central and the north-eastern Pacific.

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