Does the Pacific meridional mode dominantly affect tropical cyclogenesis in the western North Pacific?
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Does the Pacific meridional mode dominantly affect tropical cyclogenesis in the western North Pacific? Hongjie Zhang1,2 · Liang Wu1 · Ronghui Huang1 · Jau‑Ming Chen3 · Tao Feng4 Received: 8 November 2019 / Accepted: 3 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The different impacts of Pacific meridional mode (PMM) and central Pacific (CP) El Niño on tropical cyclone (TC) genesis over the western North Pacific (WNP) in the period of 1965–2018 were investigated in this study. The results show that PMM is mainly related to the eastern subtropical Pacific warming and CP El Niño is mainly related to the central tropical Pacific warming. They have a similar impact on TC genesis over the WNP and more TCs form in the east of the WNP due to the high correlation between the central tropical Pacific warming and eastern subtropical Pacific warming. In the central tropical Pacific, due to the SST forcing of the atmosphere, SST warming leads to the remarkable atmospheric response. In the eastern subtropical Pacific, the variation of the atmosphere precedes SST to establish the SST warming, and the atmospheric response to this SST warming is limited. During the CP El Niño, the anomalous convention associated with the central tropical Pacific warming produces a poleward extension of anomalous westerlies over the WNP by the Matsuno-Gill-type Rossby wave response. Such anomalous westerlies strengthen the monsoon trough (MT) with an eastward shift. The enhanced MT accompanied by the changed large-scale environmental conditions and synoptic-scale perturbations are beneficial to TC genesis over the WNP. However, the PMM with the eastern subtropical Pacific warming has no significant impact on the tropical circulation over the WNP and only a limited effect on the subtropical high. As a result, it has no direct effect on the MT, and the PMM itself has no significant positive correlation with TC genesis over the WNP. However, the impact of the PMM with the central tropical Pacific warming on TC genesis over the WNP is consistent with that during the CP El Niño. These findings suggest the dominant role of the SST warming in the central tropical Pacific on TC genesis over WNP, and the simultaneous impact of PMM on TC genesis over WNP is mainly realized by it. Keywords Tropical cyclogenesis · Pacific meridional mode (PMM) · El Niño–Southern oscillation (ENSO) · Central Pacific warming
1 Introduction
* Liang Wu [email protected] 1
Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
2
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
3
Department of Maritime Information and Technology, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan
4
College of Oceanography, Hohai University, Nanjing, China
Tropical cyclone (TC) inflicts enormous economic losses around the world. More than 30% of global TCs form over the western North Pacific (WNP), and most
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