Strong Modulation of the Pacific Meridional Mode on the Occurrence of Intense Tropical Cyclones over the Western North Pacific

Abstract

This study finds a significant positive correlation between the Pacific meridional mode (PMM) index and the frequency of intense tropical cyclones (TCs) over the western North Pacific (WNP) during the peak TC season (June–November). The PMM influences the occurrence of intense TCs mainly by modulating large-scale dynamical conditions over the main development region. During the positive PMM phase, anomalous off-equatorial heating in the eastern Pacific induces anomalous low-level westerlies (and cyclonic flow) and upper-level easterlies (and anticyclonic flow) over a large portion of the main development region through a Matsuno–Gill-type Rossby wave response. The resulting weaker vertical wind shear and larger low-level relative vorticity favor the genesis of intense TCs over the southeastern part of the WNP and their subsequent intensification over the main development region. The PMM index would therefore be a valuable predictor for the frequency of intense TCs over the WNP.

High‐Resolution Ensemble Simulations of Intense Tropical Cyclones and Their Internal Variability During the El Niños of 1997 and 2015

“…This suggests that the incidence and behavior of intense TCs (ITCs) may be more strongly related to El Niño conditions than is the total number of TCs during a given year. The distance over which the genesis location shifts appears to depend on the magnitude and location of the positive SSTA (Hong et al, 2018;Patricola et al, 2018;Wu et al, 2018), including that associated with the PMM (Gao et al, 2018;Hong et al, 2018;Zhang, Vecchi, Murakami, Villarini, & Jia, 2016).…”

Wave-driven geomorphology of Pacific carbonate coastlines: from landscape to wavelength scale

“…that PMM influences mean cyclogenesis in the WNP, with positive (negative) PMM generating anomalous vertical wind shear that causes an eastward (westward) shift in cyclogenesis (Gao et al, 2018;Hong et al, 2018). In the instrumental record positive PMM events often precede and may initiate El Nino events (Chang et al, 2007), and the eastward shift in cyclogenesis previously associated with historical El Nino events may instead be a consequence of co-occurring positive PMM (Hong et al, 2018).…”

“…Climate provides the boundary conditions that determine the frequency, geographic distribution, and intensity of TCs Gray, 1968). However, the influence of global climate is mediated by regional oceanic/atmospheric circulation that varies on seasonal to centennial timescales (Wu et al, 2012;Brandon et al, 2013;van Hengstum et al, 2016;Gao et al, 2018;Huang and Oey, 2018). To understand future TC risk and how it might change in response to anthropogenic radiative forcing, we must understand how TCs have varied in response to past forcing and the regional mechanisms governing that response.…”

“…Thus, the start of the LIA active interval may have been concurrent with the basin-wide transitions between wet and dry conditions. zonal shifts in WNP cyclogenesis over the past few decades (Hong et al, 2018;Gao et al, 2018). Thus, westward migration of the rising limb of the PWC could have shifted cyclogenesis westward during the LIA as well.…”

Superiority of Mega‐ENSO Index in the Seasonal Prediction of Tropical Cyclone Activity Over the Western North Pacific

“…The bulk of research on TCs has focused on the dynamics of TC genesis (Chia & Ropelewski, 2002; Gray, 1998), landfall (Chan & Liang, 2003; Kossin, 2018; Tuleya et al, 1984), track (Fraedrich & Leslie, 1989; Harr & Elsberry, 1991; Holland & Lander, 1993; Riehl & Shafer, 1944; Sun et al, 2017a), intensity (Camargo & Sobel, 2005; Emanuel et al, 2004), and destructiveness (Emanuel, 2005; Sun et al, 2017b). As the most active basin of TC frequency in the world (Chan, 2005), the TCs over the western North Pacific (WNP) cause serious social and economic destruction in the Asia‐Pacific region (Gao et al, 2018; Park et al, 2011; Peduzzi et al, 2012). A skillful seasonal prediction of TC activities is crucial for the preparation and reduction of TC‐related losses (Choi et al, 2016).…”