The periodicities of the other three series of the remaining stations are listed in Table 4 based on their own IMFs and Res., and their power spectra. Concisely, the series from the Fenshi station had 3.2, 4.2 and 7-year periodicities, while that of the Pingshi station had 2.2 and 4.2-year periodicities. In addition, the Lishi station series had 2.2, 4 and >6-year periodicities. Specifically, we found that, by comparison, the peak flow series at the Pingshi station was mainly dominated by short periods, while that at the Fenshi station was dominated by short and medium periods. For the Fenshi and Pingshi stations, not only short and medium periods were remarkable in the peak flow series, but also long periods.

Table 4

Results from Fourier transforms of IMF1–5 for the series at the four stations (Unit: year)

StationIMF1IMF2IMF3IMF4IMF5
Fenshi 3.2 4.2
Pingshi 2.2 4.2
Lishi 2.2 and 4 >6
Shijiao 2.1 and 4 5.9 >8
StationIMF1IMF2IMF3IMF4IMF5
Fenshi 3.2 4.2
Pingshi 2.2 4.2
Lishi 2.2 and 4 >6
Shijiao 2.1 and 4 5.9 >8

‘/’ denotes no significant periodicity is detected.

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