Correlation Coefficient Between Current Anomalies and Optimal Structure
The current (for JJA ) projection of the tropical IndoPacific SSTA pattern onto the optimal structure is -0.175 .
Penland and Sardeshmukh (1995) have shown how this optimal initial structure, obtained from Linear Inverse Modeling applied to SST anomaly data precedes a mature El Niño or La Niña event by about 7 months.
(b) Predicted pattern when (a) is used as an initial condition.
That this sequence of patterns does indeed occur in nature is verified by comparing the time series of SSTA anomaly in Niño 3.4 (6N-6S, 170W-120W) (blue line) with that of the pattern correlation between the optimal structure and the corresponding SST anomaly pattern seven months earlier (red line). For each time series plot, the corresponding scatter plot is also given, along with ONE standard deviation of scatter from best fit line. Red asterisk denotes the current Niño 3.4 SST anomaly value and the pattern correlation of the optimal structure with the SST anomaly pattern seven months before. Arrow denotes value of current projection onto the optimal structure.