Twentieth-century Pacific Decadal Oscillation simulated by CMIP5 coupled models

Abstract

The authors examine the spatial and temporal characteristics of the simulated Pacific Decadal Oscillation (PDO) in 109 historical (i.e. all forcings) simulations derived from 25 coupled models within CMIP5. Compared with observations, most simulations successfully simulate the observed PDO pattern and its teleconnections to the SSTs in the tropical and southern Pacific. BNU-ESM, CanESM2, CCSM4, CESM1-FASTCHEM, FGOALS-g2, GFDL CM3, MIROC5, and NorESM1-M show better performance. Compared with the temporal phases of the observed PDO in the twentieth century, only five simulations — from CNRM-CM5, CSIRO Mk3.6.0, HadCM3, and IPSL-CM5A-LR — simulate an evolution of the PDO similar to that derived from observation, which suggests that current coupled models can barely reproduce the observed phase shifting of the PDO. To capture characteristics of the observed PDO in the twentieth century, a requirement is that all the relevant external forcings are included in the models. How to add realistic oceanic initial states into the model may be another key point.