Fig. 1: The NPO states prior to multi-year El Niño and La Niña events in the observations and models.
From: Multi-year El Niño events tied to the North Pacific Oscillation
Normalized JFM(0) NPO indices for a the five selected multi-year El Niño events and b the seven selected multi-year La Niña events in observations. Error bars in the ensemble mean indicate the 95% confidence interval, and horizontal dashed lines represent one positive and one negative standard deviation in a, b, respectively. c Probability density functions (PDFs) of the normalized JFM(0) NPO indices for multi-year El Niño events (red curve), multi-year La Niña events (blue curve), and all winters (gray curve) in the CMIP5/6 models. d Histograms of 10,000 realizations of the bootstrap method for the normalized JFM(0) NPO indices of multi-year El Niño (red) and La Niña (blue) events in the CMIP5/6 models. Vertical red and blue lines indicate the mean values of 10,000 inter-realizations for the boreal winter NPO index before multi-year El Niño events and multi-year La Niña events, respectively. Gray shaded regions indicate the respective doubled standard deviations (SDs; the 95% confidence interval based on the normal distribution) of the 10,000 inter-realizations (see Methods). e Ratios of multi-year El Niño events preceded by NPO events (NPO), NPO without La Niña events (NPO only), La Niña occurring without NPO events (La Niña only), La Niña with NPO events (La Niña & NPO), and La Niña events (La Niña) during JFM(0) in the CMIP5/6 models. f As in e, but for the ratios of multi-year La Niña events preceded by NPO, NPO only, El Niño only, El Niño & NPO, and El Niño, respectively.
