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Jinjie Song
,
Philip J. Klotzbach
, and
Yihong Duan

Abstract

The impacts of El Niño on tropical cyclone (TC) activity over the western North Pacific (WNP) are examined through investigation of three types of tropical Pacific warming episodes according to where the maximum sea surface temperature (SST) anomalies occur in the equatorial Pacific: the eastern Pacific El Niño (EPE), the central Pacific El Niño (CPE), and the mixed El Niño (ME). More TCs form over the eastern part of the WNP in all three El Niño types, whereas the frequency of TCs over the western part of the WNP increases as the peak SST anomalies migrate from east to west. Although TCs more frequently recurve at higher latitudes during EPE and CPE, the most frequent region for recurving is much closer to the East Asian continent in CPE years than in EPE years. In contrast, more TCs track westward and threaten the Philippines in ME years. The increased TC genesis over the western part of the WNP can be explained by enhanced low-level relative vorticity, reduced vertical wind shear, and increased maximum potential intensity during CPE and increased midlevel moisture during EPE and ME. This increase is further related to updraft anomalies near the date line driven by an anomalous Walker circulation and an anomalous low-level cyclonic circulation over the WNP. The TC track differences among the different El Niño types are linked to the east–west shift of the western Pacific subtropical high, possibly caused by an anomalous Hadley circulation from 120° to 130°E that is strongly coupled with the anomalous Walker circulation.

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Lu Liu
,
Yuqing Wang
,
Ruifen Zhan
,
Jing Xu
, and
Yihong Duan

Abstract

This study investigates the trend in destructive potential of landfalling tropical cyclones (TCs) in terms of power dissipation index (PDI) over mainland China in the period of 1980–2018. Results show that both the accumulated PDI and averaged PDI after landfall show significant increasing trends. The increasing trends are found to be contributed primarily by the increasing mean duration of TCs over land and the increasing TC intensity at landfall. Further analyses indicate that the increase in landfalling TC intensity prior to and at landfall, the decrease in intensity weakening rate after landfall, and the northward shift of landfalling TC track density all contribute to the longer duration of TCs after landfall. Moreover, the conducive large-scale conditions, such as the increases in coastal sea surface temperature and land surface temperature and soil moisture, the decrease in low-level vertical wind shear, and the increase in upper-level divergence, are all favorable for intense landfalling TCs and their survival after landfall, thus contributing to the increasing destructive potential of landfalling TCs over China.

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