著者

Han LI Xuyang GE Melinda PENG Lu LI

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.100, no.5, pp.729-749, 2022 (Released:2022-09-24)

参考文献数

45

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In this study, the effect of the zonally-elongating monsoon trough (MT) on the interaction of binary tropical cyclones (BTCs) is investigated by using data analysis and idealized simulations. The interaction of BTCs is found to be sensitive to the relative orientation of the two tropical cyclones (TCs) embedded in the MT. When the two cyclones are lined up in a northeast–southwest (NE–SW) orientation, the MT steers the two cyclones to approach each other and promotes the Fujiwhara effect. In contrast, when the initial cyclones are oriented in the northwest–southeast direction of the MT, they will move away from each other under the large-scale steering flows.Idealized simulations are conducted to understand how the MT and the β-effect influence the BTC interactions, focusing on NE–SW oriented pairs. The steering flows at different stages are examined by partitioning them into the one from the MT and the other cyclone in the pair. The analysis shows that the binary TCs' motions are mainly controlled by the large-scale steering flows in the initial stage. In the case of BTCs with a NE–SW orientation, the MT can promote two TCs to approach each other, thus increasing the possibility of binary interactions.The sensitivity of the interaction of BTCs to their intensities, the strength of the MT, and the β-effect are examined. The stronger the MT, the stronger its large-scale steering flows will be, thus making the two NE–SW oriented TCs merge faster. Furthermore, the binary interaction is stronger on the β-plane compared with that on the f-plane. It is likely due to the β-induced Rossby wave energy dispersion. As the MT evolves into a monsoon gyre (MG)-like pattern, a pronounced southwesterly flow emanates in the southeast quadrant of MG. This southwesterly flow acts as a steering flow to help the western TC move northeastward, accelerating to reach the critical distance.

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.