Multi-decadal variations of ENSO, the Pacific Decadal Oscillation and tropical cyclones in the western North Pacific

In this paper, the multi-decadal variations of the Multivariate ENSO Index (MEI) and the Pacific Decadal Oscillation (PDO) index were studied to determine their influence on tropical cyclones (TCs) using the empirical mode decomposition (EMD) method and Hilbert spectral analysis. The ENSO and PDO are closely associated with various oceanic and atmospheric factors that govern TC activities in the western North Pacific (WNP). From the analysis results, multi-decadal oscillations with characteristic periods of 13 and 32.5 years from MEI, and about 16.7 and 32.8 years from PDO, were obtained. These values showed good agreement with the values obtained in other studies. The results of category 4–5 TCs and category 5 TCs also showed possible multi-decadal oscillations of about 15- and 37-year timescales, indicating that low frequency multi-decadal oscillations of intense TC occurrence in the WNP is influenced by the multi-decadal oscillations of ENSO and PDO. When seeking adaptation and mitigation measures for future climate scenarios, the multi-decadal variations of climate and their impacts on extreme events such as TCs should be taken into account together with the background of the global warming trend.