한겨울 북태평양 폭풍성 억제현상: 지역 유한 진폭 파동 활동성을 적용한 분석

학위논문 (석사)-- 서울대학교 대학원 : 자연과학대학 지구환경과학부, 2018. 2. 손석우.The North Pacific storm track, which is often quantified by band-passed filtered eddy variance, shows a relatively weak magnitude in midwinter than in adjacent seasons. This midwinter suppression of the North Pacific storm track is better characterized by local wave activity (LWA) and its budget. The LWA variance, applied to 250-hPa geopotential height field, well captures local waviness and its midwinter suppression. Although both cyclonic and anticyclonic wave activities contribute to the midwinter suppression, cyclonic wave activity (deepening of tough, cyclonic wave breaking and filamentation) exhibits a much more pronounced subseasonal cycle and explains about 73.6% of the midwinter suppression. The budget analysis of column-averaged LWA, computed for quasi-geostrophic potential vorticity, further revealed that North Pacific LWA is primarily controlled by the convergence of zonal LWA flux with a non-negligible contribution of non-conservative LWA source or sink.1. Introduction 4 2. Data and Methods 8 2.1 Data 8 2.2 Local wave activity 8 2.2.1 LWA_Z 9 2.2.2 LWA_QGPV 11 2.3 Analysis techniques 14 3. Results 15 3.1 Classical perspective of storminess 15 3.2 Local wave activity 17 3.2.1 LWA_Z 17 3.2.2 LWA_QGPV 19 3.3 Budget analysis 20 4. Summary and Discussion 22 5. References 23 Figures 26 Abstract (in Korean) 37Maste