On the Mechanisms of the Active 2018 Tropical Cyclone Season in the North Pacific

Qian, Yitian; Murakami, Hiroyuki; Nakano, Masuo; Hsu, Pang‐Chi; Delworth, Thomas L.; Kapnick, Sarah B.; Ramaswamy, V.; Mochizuki, Takashi; Morioka, Yushi; Doi, Takeshi; Kataoka, Takahito; Nasuno, Tomoe; Yoshida, Kohei

doi:10.1029/2019gl084566

Cited by 17 publications

(16 citation statements)

References 40 publications

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“…Here we aim to assess the climate drivers of the extremely active and inactive TC activity during JJA and SO of 2018, respectively. Different from Wu et al 21 and Qian et al 22 who considered the 2018 typhoon season (i.e., June to November or July to November) as an entire active season, the present study is the first attempt to unravel the physical mechanisms underlying two extreme periods in 2018 WNP TC season. 23 .…”

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confidence: 90%

“…Significance test. The significance for the anomalies in 2018 is examined by using the Monte Carlo test, which is similar to the bootstrap method used by previous studies 22,35 . The two-tailed Student t test is used to examine the significance for difference in the responses between two experiments during 80 years.…”

Section: Calculation Of Genesis Potential Index (Gpi) Gpi Is Calculamentioning

confidence: 99%

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Western North Pacific Tropical Cyclone Activity in 2018: A Season of Extremes

Zhu

Zhang

et al. 2020

Sci Rep

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The 2018 tropical cyclone (TC) season over the western North Pacific (WNP) underwent two extreme situations: 18 TCs observed during June-August (JJA) and ranked the second most active summer in the satellite era; only 5 TCs that occurred during September-October (SO), making it the most inactive period since the late 1970s. Here we attribute the two extreme situations based on observational analyses and numerical experiments. The extremely active TC activity and northward shift of TC genesis during JJA of 2018 can be attributed to the WNP anomalous low-level cyclone, which is due primarily to El Niño Modoki and secondarily to the positive phase of the Pacific Meridional Mode (PMM). Overall, the extremely inactive TC activity during SO of 2018 is due to the absence of TC formation over the South China Sea and Philippine Sea, which can be attributed to the in-situ anomalous low-level anticyclone associated with the positive phase of the Indian Ocean Dipole, although the positive PMM phase and El Niño Modoki still hold. Scientific RepoRtS | (2020) 10:5610 | https://doi.Model version 5.3 (CAM-5.3) 29 was used to perform numerical experiments. The model has T31 horizontal resolution (approximately 3.75° × 3.75°) and 26 vertical levels. Parameterization schemes adopted by the model include the deep convection scheme from Zhang and McFarlane 30 , the moist turbulence scheme from Bretherton and Park 31 , the shallow convection scheme from Park and Bretherton 32 , the stratiform cloud microphysics scheme by Morrison and Gettelman 33 , the Rapid Radiative Transfer Method for GCMs (RRTMG) radiation scheme 34 , etc. Details of the experiment design can be found in section 4.2. All the experiments were integrated for 100 years, simulations during the last 80 years were analyzed. Scientific RepoRtS | (2020) 10:5610 | https://doi.

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confidence: 90%

Section: Calculation Of Genesis Potential Index (Gpi) Gpi Is Calculamentioning

confidence: 99%

Western North Pacific Tropical Cyclone Activity in 2018: A Season of Extremes

Zhu

Zhang

et al. 2020

Sci Rep

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“…Questions were expectedly raised on what caused such unprecedented increased TC frequency in the WNP hence it is not surprising that a number of reports have already contributed to the existing knowledge pool 1 – 4 . Of the said reports, the first two studies investigated the TC frequency in the entire North Pacific (i.e.…”

Section: Introductionmentioning

confidence: 99%

Characterizing the highest tropical cyclone frequency in the Western North Pacific since 1984

Basconcillo

Cha

Moon

2021

Sci Rep

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The 2018 boreal summer in the Western North Pacific (WNP) is highlighted by 17 tropical cyclones (TC)—the highest record during the reported reliable years of TC observations. We contribute to the existing knowledge pool on this extreme TC frequency record by showing that the simultaneous highest recorded intensity of the WNP summer monsoon prompted the eastward extension of the monsoon trough and enhancement of tropical convective activities, which are both favorable for TC development. Such changes in the WNP summer monsoon environment led to the extreme TC frequency record during the 2018 boreal summer. Meanwhile, the highest record in TC frequency and the intensity of the WNP summer monsoon are both attributed with the combined increase in the anomalous westerlies originating from the cold tropical Indian Ocean sea surface temperature (SST) anomalies drawn towards the convective heat source that is associated with the warm central Pacific SST anomalies. Our results provide additional insights in characterizing above normal tropical cyclone and summer monsoon activities in the WNP in understanding seasonal predictable horizons in the WNP, and in support of disaster risk and impact reduction.

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“…TC activity and the role of the SST anomaly within a specific year or for an event have been investigated using short‐term ensemble AGCM simulations (Murakami et al., 2017; Qian et al., 2019; Takaya, 2019; Yamada et al. 2019).…”

Section: Introductionmentioning

confidence: 99%

“…2019). Furthermore, the contribution of the Pacific meridional mode (PMM: Chiang & Vimont, 2004) has been investigated (Gao et al., 2018; Qian et al., 2019; Takaya, 2019; Zhang et al. 2016).…”

Section: Introductionmentioning

confidence: 99%

Potential Predictability of the Tropical Cyclone Frequency Over the Western North Pacific With 50‐km AGCM Ensemble Experiments

et al. 2021

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The potential predictability determined by sea surface temperature (SST) of the frequency distribution of tropical cyclones (TCs) is studied using ensemble simulations with a 50‐km resolution atmospheric general circulation model (AGCM). In this experiment, the interannual variability of the TC frequency over the western North Pacific (WNP) is primarily determined by SST, as the simulated ensemble mean signal is dominant over the ensemble spread and effectively follows the observed TC frequency in June‐July‐August (JJA). In contrast, the correlation between the observed and simulated TC frequency variability is less significant in September‐October‐November (SON). To explore the TC frequency‐SST linkage, the relationship between the TC frequency variability over the WNP and climate modes determined by SST indices is investigated. Through a correlation analysis, we found that El Niño Modoki is the major driver of the TC frequency variability over the WNP in JJA. Partial correlation analysis further reveals that internal atmospheric dynamics are important for the TC frequency variability over the WNP in SON. These results suggest that the tropical climate mode is responsible for the seasonal predictability of the TC frequency variability over the WNP and that the prediction skill is seasonally dependent with a high (low) skill in JJA (SON).

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On the Mechanisms of the Active 2018 Tropical Cyclone Season in the North Pacific

Cited by 17 publications

References 40 publications

Western North Pacific Tropical Cyclone Activity in 2018: A Season of Extremes

Western North Pacific Tropical Cyclone Activity in 2018: A Season of Extremes

Characterizing the highest tropical cyclone frequency in the Western North Pacific since 1984

Potential Predictability of the Tropical Cyclone Frequency Over the Western North Pacific With 50‐km AGCM Ensemble Experiments

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