Multiscale Relationships Between ENSO and Tropical Cyclones Over the Western North Pacific (1950–2024) An Empirical Study Based on Wavelet Analysis

Based on tropical cyclone data from the China Meteorological Administration and the Oceanic Niño Index data, this study statistically analyzed the intensity changes of ENSO events and characteristics such as the frequency and intensity of typhoons in the Northwest Pacific over the past nearly 75 years (1950–2024). Wavelet analysis was employed to examine the time-frequency characteristics of ENSO and its correlation with Northwest Pacific tropical cyclons (referred to as typhoons in the Northwest Pacific). The results indicate that: 1) ENSO exhibits an interannual oscillation with a timescale of 94 months (approximately 5-year cycle) and an interdecadal oscillation with a timescale of 198 months (approximately 10–11 year cycle). 2) Over the past 75 years, the frequency of Northwest Pacific typhoons and landfalling typhoons has significantly decreased, while the landfall intensity has significantly increased; typhoon frequency is highest in August and lowest in February, while typhoon intensity is strongest in October and weakest in February. 3) On the interannual scale, there is a negative correlation between ENSO and typhoon frequency, as well as landfalling typhoon frequency, at the 2–6 year timescale, with moderate significance, and typhoon changes slightly lead ENSO; there is a positive correlation between ENSO and average typhoon intensity, as well as average landfalling typhoon intensity, at the 2–6 year and 10–15 year timescales, with strong significance, and ENSO changes slightly lead typhoon changes. 4) On the monthly scale, the negative correlation between ENSO and typhoon frequency is more significant than on the interannual scale, whereas the positive correlation between ENSO and average typhoon intensity is less significant than on the interannual scale. Furthermore, the positive/negative correlation between ENSO and typhoon frequency shows different directions depending on the chosen cycle scale.