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Development of the East Asian Cyclones: A Potential Vorticity Perspective
Seok-Woo Son,Joonsuk M. Kang 한국기상학회 2021 한국기상학회 학술대회 논문집 Vol.2021 No.10
The development processes of the extratropical cyclones passing the Korean Peninsula during the period of 1979-2017 are quantitatively evaluated in the potential vorticity (PV) perspective. A feature tracking algorithm is applied to the ERA-Interim reanalysis data to objectively identify the distinct northern- and southern-track (NT and ST) cyclones affecting the region in the cool season. The dynamic and thermodynamic contributions to the development of these two categories of cyclones are then comparatively assessed. With respect to the 850- hPa geostrophic relative vorticity tendency resulting from the PV tendency inversion, it is quantified that the NT cyclones develop 87.9% dynamically and 6.2% thermodynamically. In contrast, the respective contributions are 71.8% and 43.5% for the ST cyclones. The excessive or insufficient contributions are complemented by non-explicit processes. In both NT and ST cyclones, the zonal PV advection in the upper troposphere is the most influential for the dynamic development, while nonlinear advection being more important in the former. The larger thermodynamic contribution of the latter is attributed to more latent heating being involved in the development, which produces more lower-level PV and reduces damping from vertical PV advection. These results indicate that East Asian cyclones passing the Korean Peninsula have different development processes depending on their tracks.
동아시아 대도시에 영향을 미치는 온대저기압의 특성 및 강수 영향 비교: 서울, 베이징, 도쿄
김동현(Donghyun Kim),이재연(Jaeyeon Lee),강준석(Joonsuk M. Kang),손석우(Seok-Woo Son) 한국기상학회 2021 대기 Vol.31 No.1
The synoptic structures and precipitation impact of extratropical cyclones (ETCs) influencing on the three adjacent megacities in East Asia, i.e., Beijing (Beijing ETCs), Seoul (Seoul ETCs) and Tokyo (Tokyo ETCs), are analyzed using ERA-interim reanalysis data from 1979 to 2018. Individual ETC tracks are identified with the automated tracking algorithm applied to 850-hPa relative vorticity field. Among four seasons, ETCs are the most frequent in spring. In this season, Beijing ETCs are mainly generated at the leeside of Altai-Sayan Mountains and primarily develop through interaction between the upper-level trough and lower-level cyclonic circulation. For Seoul ETCs, the leesides of Altai-Sayan Mountains (Seoul-N ETCs) and Tibetan Plateau (Seoul-S ETCs) are main genesis regions and the features of ETCs are different according to the genesis regions. While Seoul-N ETCs mainly develope by the same mechanism of Beijing ETCs, strong diabatic heating due to vapor transport is responsible for the genesis of Seoul-S ETCs. Tokyo ETCs are originated from the leesides of Tibetan Plateau and Kuroshio-Oyashio Extension regions, and strong diabatic heating as well as interaction between upper and lower levels determines the genesis of these ETCs. The precipitation impact resulting from ETCs become strong in the order of Beijing ETCs, Seoul-N ETCs, Seoul-S ETCs, and Tokyo ETCs and accounts for up to 40%, 27%, 52%, and 70% of regional precipitation, respectively.