Changes in Western Pacific Tropical Cyclones Associated with the El Niño–Southern Oscillation Cycle

• Published in: Journal of climate Vol. 25; no. 17; pp. 5864 - 5878
• Main Authors: Li, Richard C. Y., Zhou, Wen
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.09.2012
• Subjects: Climate change; Climate variability; Cyclones; Earth, ocean, space; El Nino; Environmental factors; Exact sciences and technology; External geophysics; La Nina; Marine; Meteorology; Monsoons; Oceans; Relative humidity; Southern Oscillation; Studies; Time series; Tropical cyclones; Tropical depressions; Typhoons; Vorticity; Wind; Wind shear; West Pacific; Equatorial Pacific; Pacific Ocean; IW, Pacific; IS, Tropical Pacific; Environmental factor; Empirical orthogonal function; climate variability; wavelet transformation; Heat content; Interannual variation; Typhoon; El Nino; Severe weather; Correlation analysis; Tropical cyclone; Southern oscillation; Vorticity; Timing; Wind shear; Comparative study; La Nina
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI-D-11-00430.1

This study examines the interannual variability of three groups of tropical cyclones (TCs)—super typhoons (STYs), typhoons (TYs), and tropical storms and tropical depressions (TSTDs)—and their relationship with the El Niño–Southern Oscillation (ENSO). Both wavelet analysis and correlation studies of upper-ocean heat content reveal significant differences for the three types of TCs. In particular, an increase (decrease) in the frequency of STYs is usually associated with the mature phase of El Niño (La Niña) events, while the converse is true for TSTDs. In contrast, the frequency of TYs increases (decreases) during the transition period from La Niña to El Niño (El Niño to La Niña) events. The results suggest that the timing with which ENSO impacts STYs, TYs, and TSTDs varies and that their corresponding changes in frequency closely follow the evolution of the ENSO cycle. Empirical orthogonal function analysis is also conducted to investigate the impact of different environmental factors influenced by ENSO on TCs. The vertical wind shear and moist static energy associated with ENSO are identified as the dominant factors that control the frequency of STYs. In comparison, the frequency of TYs is found to be closely related to the relative vorticity and vertical wind shear associated with both the transition phase of ENSO and with other types of climate variability.