The results indicate that :
The streamfunction PC analysis also exhibits an ENSO type response as the dominant mode, but this accounts for only 8% to 21% of the variance.
The CPC analysis allows a direct comparison of the data from all the models on a common set of vectors. The component identified with the ENSO mode represents 27% to 52% of the variance explained for the divergence in this formulation. These results indicate that the models share a basic common pattern but there is a strong variation in the amplitude of the corresponding modes.
The variance explained by the leading mode for the CPC streamfunction is between 5% and 19%, and there is less commonality in the higher components than seen in the divergence. This appears to be related to the stronger streamfunction response in the mid-latitudes, which is presumably more affected by nonlinearity and intrinsic variability of the model integrations.
Based on results using an ensemble of five decadal runs using the ECMWF GCM an estimate is made of the variation of explained variance due to intrinsic variability for a single model. It is found that in general the inter-model variation is somewhat greater than the intra-model ensemble variation using the ECMWF model.
A probability density function (PDF) analysis in the space spanned by the first two CPCs for the velocity potential ( which explain over 70% of the variance for all but one model) yields distinctive dynamical signatures. Some models populate a somewhat larger PDF space than others.