EOFs

eof_1.ncl: Read sea level pressure (1979-2003) and calculate the first two eigenvectors over the North Atlantic region for the winter (DJF) season. The first EOF pattern is commonly identified as the North Atlantic Oscillation (NAO) mode.

lonFlip is used to rearrange the data to span -180 to 180. Then coordinate subscripting is used to extract the region of interest.

Finally, the resulting principal component time series is normalized by the weights used to get the time series of the mean areal amplitudes. The example uses eofunc and eofunc_ts (available since version 4.2.0.a032). These replace the deprecated functions: eofcov, eofcor, eofcov_pcmsg, eofcor_pcmsg, eofcov_ts, and eofcor_ts.