Influence of ENSO Events on Tropical Cyclone Activity over the Western North Pacific

Abstract

Based on an analysis of 51-year (1965–2015) data, the influence of El Nino-Southern Oscillation (ENSO) events on tropical cyclone (TC) activity is examined over the western North Pacific (WNP). The total number of TCs formed in the entire WNP reduces by about 3.4 TCs per year in La Nina years, whereas TCs have an equivalent genesis number between El Nino years and climatology. During El Nino years, the frequency of TC formation increases remarkably in the southeast quadrant (140°E–180°, 0°–17°N) and decreases in the northwest quadrant (120°–140°E, 17°–30°N). During La Nina years, TCs tend to form in the northwest and southwest quadrants (120°-140°E, 0°–17°N) quadrants. TCs tend to become long-lived in the peak season (from July to September) of El Nino years and during strong El Nino events. TC genesis shows a southeastward positive shift in terms of lifetime and intensity during El Nino years, thus more super TCs (winds ≥ 58.64ms−1) are formed in the southeast quadrant. Further analysis using the genesis potential index (GPI) indicates that the interannual variations in the TC genesis and track are significantly influenced by a combination of large-scale dynamic and thermodynamic conditions.