Abstract
By using the POP (principal oscillation pattern) system matrices as examples, this study introduces to the meteorological community the concept and application of spectral portrait (or pseudospectra) of a nonsymmetric matrix. An analytical formula is provided to estimate the system error of a POP matrix due to the inversion of a covariance matrix. By comparing the spectral portrait and the system error, this study demonstrates a possible tool to test the sensitivity of a POP analysis.
Corresponding author address: Yuang Zhang, Max-Planck-Institut für Meteorologie, Bundesstrasse 55, D-20146 Hamburg, Germany.