Investigating the abrupt change of tropical cyclone (TC) activity in the Western North Pacific by using different TC genesis indices

Li Peng Hsiao, Chih Hua Tsou, Jia Yuh Yu*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The tropical cyclone (TC) genesis indices are used to investigate the abrupt change of TC genesis frequency (TCGF) in the Western North Pacific (WNP) from 1979 to 2014 and to discuss the factors leading to the abrupt change. This study shows that TCGF had an abrupt decrease in 1997, but the popular TC genesis indices used in recent studies do not reflect this feature. An appropriate TC genesis index must consider both thermal and dynamic effects to reflect the TCGF abrupt change in the WNP. We modify the dynamic and thermal effects of the existing indices and propose a new TC genesis index, MoχGPI, which is consistent with the observational abrupt change of TC activity regardless of spatial distribution or time-series patterns. A budget analysis of MoχGPI is conducted to discuss the individual contribution of large-scale environmental parameters to the TCGF abrupt change. The results show that the change in relative vorticity (including contributions not only from the environmental relative vorticity, but also a part from the relative vorticity by TCs themself) is the dominant effect leading to the TCGF abrupt change in 1997, followed by the vertical wind shear effect.

    Original languageEnglish
    Pages (from-to)5959-5972
    Number of pages14
    JournalInternational Journal of Climatology
    Volume40
    Issue number14
    DOIs
    Publication statusAccepted/In press - 2020

    Keywords

    • abrupt change
    • tropical cyclone genesis frequency
    • Western North Pacific

    ASJC Scopus subject areas

    • Atmospheric Science

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