Long term ocean/atmospheric data sets contain signals that overlap in space and time. Removal of the ENSO signal helps EOF-like analyses to isolate Pacific Pan-decadal Variability (PDV) as one of the primary long-term climate variations at middle and low latitudes in observation and reanalyses datasets.

A comprehensive picture of PDV as manifested in the troposphere and at the surface is described. In general, the PDV spatial patterns in different parameter fields share some similarities with the patterns associated with ENSO, but important differences exist. First, the PDV circulation pattern is shifted westward by about 20° and is less zonally extended than that for ENSO. The westward shift of the PDV wave train produces a different North American teleconnection pattern that is more west-east oriented. The lack of a strong PDV surface temperature signal in the west equatorial Pacific and the relatively strong surface temperature signal in the subtropical regions are consistent with an atmospheric overturning circulation response that differs from the one associated with ENSO. Our analysis also suggests that PDV is a combination of decadal and/or interdecadal oscillations interacting through teleconnections.

Similar analysis methods are applied on the WCRP CMIP3 multi-model dataset (also known as IPCC AR4 CGCM simulations) to evaluate the PDV simulation in current coupled GCMs. The relationships between PDV simulation and ENSO simulation are also investigated.