Fig. 1: The reference PMM-T and alternative indices.
From: Disentangling the North Pacific Meridional Mode from tropical Pacific variability
a Regression of the Pacific Meridional Mode (PMM) index (derived via MCA) onto anomalies of SST (°C, shading), surface winds (m s−1, vectors), and sea-level pressure (contours, interval of 0.25 hPa). Negative contour lines are dashed and the 0-contour line is omitted. Only values significant at the 95% confidence level are shown. b Similar to (a), but for the expansion coefficient of a principal component analysis of SST (PMM_EOF). c Similar to (a), but for an index that is simply the area average of SST anomalies in the gray box, and without removing ENSO variability beforehand. d Like (a), but using a more thorough way of removing ENSO variability (see text). e Time series of three of the indices in (a), (c), and (d), normalized by their respective standard deviations. The time series of (b) is not shown as it is very similar to that of (a). All fields are from the NCEP/NCAR Reanalysis.
