This study analyzed the change in tropical cyclone (TC) activity according to the fluctuation in July-to-September average North Pacific Oscillation index (NPOI) and its underlying large-scale environment during the last 37 years from 1977 to 2013. For this purpose, seven years with highest index NPOI value (positive NPOI phase) and another seven years with lowest NPOI index value (negative NPOI phase) among the 37 years were selected as sample after excluding the ENSO years.
During the positive NPOI phase, TCs were created in the east of tropical and subtropical western North Pacific and moved to the west from the Philippines toward the southern region in China or toward far eastern sea of Japan. Meanwhile, during the negative NPOI phase, TCs tended to proceed to the north toward Korea or Japan passing East China Sea from the eastern sea of the Philippines. As a result, also in the TC recurvature, TCs in positive NPOI phase showed a tendency of recurving toward more eastern direction compared to TCs in negative NPOI phase. Hence, TC intensity was stronger in negative NPOI phase which allowed more time for obtaining energy from the ocean.

Abstract
 1. 서 론
 2. 자료 및 분석방법
  2.1. 자료
  2.2. 분석방법
  2.3. 북태평양 진동 지수
 3. 시계열 분석
 4. 양의 북태평양 진동 지수 해와 음의 북태평양 진동지수 해 사이의 차
  4.1. 태풍활동
  4.2. 종관환경
 5. 요약 및 결론
 REFERENCE

• 최기선(국립기상과학원 연구기획운영과) | Choi Ki-Seon (Planning and General Affairs Division, National Institute of Meteorological Research) Corresponding author
• 이경미(국립기상과학원 연구기획운영과) | Kyungmi Lee (Planning and General Affairs Division, National Institute of Meteorological Research)
• 김정윤(국립기상과학원 연구기획운영과) | Jeoung-Yun Kim (Planning and General Affairs Division, National Institute of Meteorological Research)
• 박철홍(국립기상과학원 연구기획운영과) | Cheol-Hong Park (Planning and General Affairs Division, National Institute of Meteorological Research)