An Abrupt Slowdown of Late Season Tropical Cyclone over the Western North Pacific in the Early 1980s

  • WANG Chao
    Key Laboratory of Meteorological Disaster of Ministry of Education, International Research Laboratory of Climate and Environment Change and Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, China Beijing Regional Climate Center, China
  • WU Liguang
    Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, China
  • ZHAO Haikun
    Key Laboratory of Meteorological Disaster of Ministry of Education, International Research Laboratory of Climate and Environment Change and Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, China
  • LIU Qingyuan
    Jiangsu Institute of Meteorological Sciences, China
  • WANG Ji
    Beijing Regional Climate Center, China

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Other Title
  • 1980年代初頭の北西太平洋における晩期の熱帯低気圧の急激な減速

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Abstract

<p>Translation speed is an important factor determining locally accumulated disasters induced by tropical cyclones (TCs). We found that the basin wide TC translation speed over the western North Pacific (WNP) in the late season (October–December) experienced an abrupt decrease in the early 1980s. However, this slowdown cannot be explained by the previously proposed deceleration in large-scale steering. In this study, we demonstrated that this slowdown results from the decreased proportion of subtropical TC track frequency in the early 1980s. Because late-season large-scale steering flow in the subtropical WNP is much greater than that in the tropical WNP, TCs influencing the subtropical WNP generally hold greater translation speed than that of TCs staying in the tropical WNP. Thus, a decrease in the ratio of subtropical TC track frequency can lead to a notable decrease in the basin wide TC translation speed. The decreased ratio of subtropical TC track frequency results from the strengthened southwestward steering and the reduced ratio of TC genesis in the tropical eastern WNP, which is linked to a WNP anticyclonic circulation that appears to be driven by the Atlantic Multi-decadal Oscillation. The result introduces the crucial role of TC track shift in the basin wide TC translation speed and has important implications for understanding the effects of climate change on TC translation speed.</p>

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