著者

Qijun HUANG Xuyang GE Melinda PENG

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.98, no.6, pp.1335-1352, 2020 (Released:2020-12-18)

参考文献数

46

被引用文献数

1

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In this study, the Advanced Weather Research and Forecasting (WRF-ARW) model is used to investigate possible influences of a predominantly upper-level easterly wave (EW) on Typhoon Megi's (2010) sharp northward turn on 20 October, 2010 after passing over the Philippines. Observational analysis indicates that an upper-level EW with a cold-cored structure was located to the east of Megi. This EW moved westward along with Megi and modified the large-scale environmental flow around the typhoon, thus affecting its movement. In a control experiment, the sharp northward turn that was observed was captured well by a simulation. The retreat of the subtropical high contributed directly to the poleward steering flow for Megi. Sensitivity experiments were conducted by filtering out the synoptic-scale (3–8-day) signals associated with EWs. In the absence of the upper-level EW, the simulation showed that Megi would not have made a sharp northward turn. Two mechanisms are proposed regarding the impact of the easterly wave on Megi. First, an upper-level EW may have impacted the environmental flows, allowing Megi to move at a slower westward speed so that it entered the eastern semicircle of the nearby monsoon gyre where an enhanced southerly steering flow then led to the typhoon making a sharp northward turn. Second, the diabatic heating and associated cyclonic vorticity induced by the middle-level (around 400 hPa) convergence may have eroded the western flank of the subtropical high in the western North Pacific, causing an eastward retreat of the high-pressure system. The present modeling approach provides a reasonable assessment of the contribution of upper-level wave disturbances to sudden changes in tropical cyclones.