In the WNP, the TC season depend heavily on its start date which have large interannual variation and the start date controlled by SST over the IO and the EP. ENSO-like SST anomalies (i.e. anomalous warm SST over the IO and the EP) weaken Walker circulation and induce surface divergence and descent over the WNP which is the TC formation region. It causes anomalous anticyclone over the WNP in the winter and this anomaly lasts until the spring. This mechanism plays a role in inhibiting the TC formation by suppressing convection. As a result, the start of the TC season in the WNP is delayed and the length of the season which is rely on its start becomes shorter. It implies that not only local SST warming, but also tropical SST distribution is important factor to predict TC activity in the WNP.
In terms of long-term variation, as mentioned in section 3.1, the TC season in the WNP getting shorter for the last 64 years with the delay of its start.
But actually, though global SST is rising due to the global warming, TC season in the WNP have been delayed less than expected. The start date of the TC season is delayed about 0.26 days a year (Table 1) and this trend is not statistically significant. Although the long-term trends are insignificant and weak, it is notable because it contrasts with the trend of the hurricane season (Kossin, 2008). Kossin (2008) suggested that the hurricane season is getting longer, as the dates of occurrence of the first and last hurricanes have decreasing and increasing trend, respectively. Local SST warming in the hurricane developing region is interpreted as the reason. However, in case of TC in the WNP, local SST does not affect the length of the TC season. TC
activity in the WNP is associated to the remote SST variations and related atmospheric conditions over the WNP. But due to the large uncertainty in the insignificant long-term variation of the TC season in the WNP, unfortunately, the environmental factors that affect the long-term variation of the TC season in the WNP remain unknown.
Acknowledgments
2014년 3월, 많은 걱정을 안고 석사과정을 시작했었는데 어느새 이렇게 졸업을 하게 되었습니다. 졸업을 하기까지 많은 분들의 도움이 있었지만 가장 먼저 부족한 점 많았 던 첫 제자를 처음부터 하나 하나 지도해 주신 김형석 교수님께 감사드립니다. 연구실 선배가 없어 교수님께 직접 여쭤볼 수밖에 없었는데, 교수님께서 잘 이끌어주신 덕분에 짧은 대학원 생활 동안 많은 것을 배우고 성장할 수 있었습니다. 입학을 하고 나서도 잘 해낼 수 있을지 걱정과 고민이 많았지만, 항상 모자란 것 보다는 잘한 것부터 봐주 시고 격려해주신 덕분에 이렇게 졸업까지 올 수 있었습니다.
또한 학부 때 대기과학을 공부하여 해양 분야는 전혀 모르던 저에게 많은 가르침을 주신 이호진 교수님과 이경은 교수님께 감사드립니다. 해양 분야 대학원 수업이 힘들기 도 했지만 교수님들께서 잘 가르쳐 주신 덕분에 극지해양과 고해양학 분야에도 흥미를 가지게 되었고 재미있게 수업을 들었습니다. 같이 수업을 들으며 제게 도움을 주셨던 미옥 언니와 상엽 오빠, 은선이, 령아에게도 감사합니다. 제 논문에 대해 다양한 조언과 함께 정성 어린 심사를 해주신 박두선 박사님께도 감사드립니다.
학회에 갈 때 마다 연구실 동료가 없는 저를 챙겨주신 UNIST의 기후환경모델링 연구 실(UCEM) 학생분들과 이명인 교수님, 박명숙 박사님께도 감사드립니다. 특히 항상 같은 방을 쓰며 언니처럼 챙겨주고 많은 조언을 해주신 혜림 언니에게 감사하다는 말씀 드리 고 싶습니다.
처음 연구실에 들어와서 혼자 외로울 무렵 연구실에 들어온 형석이와 소진이, 그리고 2년 동안 같은 방에 살았던 예은이에게도 고맙습니다. 덕분에 외롭지 않게 대학원 생활 을 할 수 있었습니다.
마지막으로 언제나 믿어주시고 응원해주시는 부모님과 할머니 할아버지, 든든한 동생 에게 감사하며 이렇게 고마운 분들을 생각하며 앞으로 더욱 발전하는 사람이 되도록 하 겠습니다.
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