Abstract
Understanding of the El Niño phenomenon is improving and several studies have considered the dynamics of El Niño diversity, however, the important role of tropical cyclones has rarely been reported. Here we show a clear feedback of tropical cyclones (TCs) over the western North Pacific (WNP) on the El Niño diversity. Strong (weak) accumulated cyclone energy helps to shift the center of strongest sea surface temperature anomalies 3 months later to the equatorial eastern (central) Pacific, and thus supporting the development of the eastern-Pacific (central-Pacific) El Niño. Local sea surface temperature anomalies in the Niño-3.4/Niño-3/Niño-4 region and tropical western Pacific, zonal wind anomalies over the tropical central-western Pacific and Madden‒Julian Oscillation play small roles in the process that WNP TCs affect El Niño diversity. Moreover, the greater number of central-Pacific El Niño events after 1999/2000 may be associated with weaker accumulated cyclone energy in this period.
Highlights
The first part of this two-part study explores the feedback of the western North Pacific (WNP) tropical cyclones (TCs) on El Niño diversity from two aspects, including the traditional types of El Niño events (EP and CP El Niño) and El Niño cases related to the preceding accumulated cyclone energy (ACE) events (El Niño_strong ACE and El Niño_weak ACE)
From the perspective of the El Niño cases related to the preceding ACE events, results indicate the center of the maximum sea surface temperature (SST) anomalies during El Niño_strong ACE is located in the equatorial eastern Pacific, showing the spatial pattern of EP El Niño; On the contrary, the center during El Niño_weak ACE moves to the central-western Pacific, showing the spatial pattern of CP El Niño
Overall, when the preceding ACE is strong, it favors the occurrence of EP El Niño events; when the preceding ACE is weak, it favors the occurrence of CP El Niño events
Summary
Since the pioneering study of El Niño–South Oscillation (ENSO) by Bjerknes (1969), considerable research has been devoted to the study of ENSO because of its large-scale effects (Wyrtki 1985; Zebiak and Cane 1987; Schopf and Suarez 1988; Battisti and Hirst 1989; Jin 1997; Weisberg and Wang 1997; Wang and Chan 2002; Chen et al 2004; Chan 2007; Jin et al 2014; Wang et al 2016; Ding et al 2017; Xie et al 2018; Ren et al 2020). Wang et al (2019) found that the preceding (3 months earlier) WNP TCs could affect the El Niño intensity by a cumulative effect: the greater the ACE, the stronger the El Niño, for TCs in July–September. Most studies have focused on the different influences of the distinct types of El Niño on the TCs over the WNP. Some studies on the climate effect of TCs have been proposed, little is known about the feedback of TCs on El Niño diversity defined by the location of the maximum SST anomalies (in short, El Niño diversity).
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