Wavelet analysis of precipitation extremes over Canadian ecoregions and teleconnections to large-scale climate anomalies

摘要

To detect significant interannual and interdecadal oscillations and their teleconnections to large-scale climate anomalies such as El Ni?o–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO), monthly and seasonal maximum daily precipitation (MMDP and SMDP) from 131 stations across Canada were analyzed by using variants of wavelet analysis. Interannual (1–8 years) oscillations were found to be more significant than interdecadal (8–30 years) oscillations for all selected stations, and the oscillations are both spatial and time-dependent. Similarly, the significant wavelet coherence and the phase difference between leading principal components of monthly precipitation extremes and climate indices were highly variable in time and in periodicity, and a single climate index explains less than 40% of the total variability. Partial wavelet coherence analysis shows that both ENSO and PDO modulated the interannual variability and PDO modulated the interdecadal variability, of MMDP over Canada. NAO is correlated with the western MMDP at interdecadal scale and the eastern MMDP at interannual scale. The composite analysis shows that precipitation extremes at about three fourths of the stations have been significantly influenced by ENSO and PDO patterns, while about one half of the stations by the NAO patterns. The magnitude of SMDP in extreme El Ni?o years, and extreme PDO event of positive phase, was mostly lower (higher) over the Canadian Prairies in summer and winter (spring and autumn) than in extreme La Ni?a years. Overall, the degree of influence of large-scale climate patterns on Canadian precipitation extremes varies by season and by region.