文摘
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Summary
The re-occurrence pattern of major extremes in hydrology, such as the timing and intensity of river floods, is related to a variety of natural and anthropogenic factors. In this study, the particular temporal regional influence of ?1 year solar radiation cyclicities on the maximum annual streamflow (MAS) records from six stations from four eco-zones in Southern Canada were investigated. Wavelet analysis decomposition and re-composition techniques were applied to extract the ?1 year signals in the hydrological records. An ?1 year cyclicity is evident in all eco-zones but it is superimposed by non-periodic variability in the 2 to 18 year wavebands that are due to El Nino/Southern Oscillation and North Atlantic Oscillation related precipitation variability or random components in the records. The ?1 year MAS cyclicity is strong in the Mountain ecozone (Rocky Mountains) and less strong in the Boreal Shield. In these eco-zones, it was found that years that experienced major floods were most likely to occur during low sunspot number years, in the spring time approximately 6-7 years after the last solar maximum. The results of the wavelet analysis demonstrate that major floods are more likely to occur during sunspot cycles with relatively low sunspot numbers after the last maximum.
