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Investigating the abrupt change of tropical cyclone (TC) activity in the Western North Pacific by using different TC genesis indices
Author(s) -
Hsiao LiPeng,
Tsou ChihHua,
Yu JiaYuh
Publication year - 2020
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.6558
Subject(s) - tropical cyclone , climatology , vorticity , wind shear , environmental science , climate change , cyclone (programming language) , atmospheric sciences , geology , meteorology , wind speed , oceanography , geography , vortex , computer science , computer hardware , field programmable gate array
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.