Wavelet analysis INDEX

The common oscillations were consistent during the whole 45 years period, as revealed by cross-wavelet analysis (Fig. 5). Analysis for streamflow, ENSO index, and AF indicates a persistent common power for oscillations with period between 30 and 65 months, which appears to vary according to the intensification and weakening of the quasibieimial and quasiquadrennial band of ENSO. 

To compare the changes in correlation between the NIN03 index and the Danube discharge seasonal anomalies, we used cross-wavelet transform software, produced by Aslak Grinsted. The details of cross-wavelet analysis methodology are given in [19-21]. 

In this representation, integer j indexes the scale or resolution of analysis, i.e., smaller j corresponds to a higher resolution, and jo indicates the coarsest scale or the lowest resolution, k indicates the time location of the analysis. For a wavelet 4> t) centered at time zero and frequency u>o, the wavelet coefficient dj k measures the signal content around time 2 k and frequency 2 uio- The scaling coefficient Ck measures the local mean around time 2 °k. The DWT represents a function by a countable set of wavelet coefficients, which correspond to points on a 2-D grid of discrete points in the scale-time domain. 

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