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The Intensification of Walker Circulation over the Past 15 Years from 1999 and Its Relation to TC Activity in the Western North Pacific KCI 등재

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한국지구과학회지 (The Journal of The Korean Earth Science Society)
한국지구과학회 (The Korean Earth Science Society)
초록

The time-series of Walker circulation index (WCI) in this study shows the strengthening of the Walker circulation in recent years. To further understand the large-scale features related to the WCI strengthening, a difference between the averaged meteorological variables in two time periods 1999-2013 and 1984-1998 is analyzed. The difference in 850 hPa stream flows between the two periods shows that the anomalous easterlies (anomalous trade wind) are dominant due to the strengthening of anomalous anticyclonic circulations at the subtropical Pacific of both hemispheres. The difference between the averaged zonal atmospheric circulations over 5oS-5oN in the two periods confirms that upward flows are strengthened at the tropical western Pacific and downward flows are strengthened at the tropical central and eastern Pacific in recent years. It matches the WCI strengthening in recent years. The time-series of tropical cyclone (TC) genesis frequency from July to September shows that a mean TC genesis frequency from 1999-2013 decreases compared to that of the time period 1984-1998. The monsoon trough in the period 1984-1998 was located in the further east direction and stronger than that in the period 1999-2013. TCs in the recent period that are generated in further west than TCs in the past period moved from the west. Thus, the TC intensity along the coasts in East Asia becomes weaker in recent period. The intensification of Walker circulation in recent years is related to the weaker TC intensity in East Asia through strengthened anomalous anticyclones at the subtropical western Pacific.

목차
1. Introduction
 2. Data and Methods
  2.1. Data
  2.2. Methods
 3. Time Series Analysis
 4. Differences between 1999-2013and 1984-1998
  4.1. Large-scale environments
  4.2. TC activity
 5. Summary and Conclusion
 References
저자
  • Jae-Won Choi(Research Planning and Management Division/National Institute of Meteorological Sciences, Jeju, Korea) Corresponding author
  • Yumi Cha(Research Planning and Management Division/National Institute of Meteorological Sciences, Jeju, Korea)
  • Jeoung-Yun Kim(Research Planning and Management Division/National Institute of Meteorological Sciences, Jeju, Korea)