A Numerical Investigation of Track and Intensity Evolution of Typhoon Doksuri (2023)

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Title:	A Numerical Investigation of Track and Intensity Evolution of Typhoon Doksuri (2023)
Authors:	武妙紅;Hong, Vu Dieu
Contributors:	大氣科學學系
Keywords:	颱風Doksuri;Typhoon Doksuri
Date:	2024-07-23
Issue Date:	2024-10-09 14:44:57 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究利用WRF模式模擬颱風杜蘇芮Doksuri (2023)。首先透過一系列的敏感性實驗來選擇最佳的參數化方案。實驗結果顯示，Grell–Freitas Ensemble積雲參數化和NSSL雙變數微物理參數化的組合在模擬杜蘇芮的路徑和強度表現最佳。後續會進行更深入的分析以探討颱風路徑和強度變化的機制。杜蘇芮起初往西北方向移動，但在接近菲律賓北部時轉為向西移動。而12小時之後颱風再次轉向，恢復往西北方向移動。本研究使用位渦收支趨勢診斷來解釋此路徑變化。分析結果指出，位渦收支趨勢的水平平流項是促使颱風向西偏轉的主要原因。在強度方面，杜蘇芮颱風經歷了快速增強的階段。在研究此一過程中，發現颱風內核中對流雲的增加表示有深對流生成的現象。這會導致強烈的熱能釋放，提高加熱效率，颱風強度也隨之增強。此外利用展開的Sawyer–Eliassen方程式來決定何者為颱風增強的主要因素。結果顯示，非絕熱加熱對於增強次環流的作用扮演相當重要的角色。 ;This study uses the WRF model to simulate Typhoon Doksuri (2023). First, a series of sensitivity microphysics and cumulus scheme tests are conducted to select optimal parameterization schemes. The results indicate that a combination of the Grell–Freitas Ensemble cumulus scheme and the NSSL 2-moment microphysics scheme is the most effective in reproducing both the track and intensity of Doksuri. Subsequently, further analysis will be performed to explore the mechanisms of typhoon track and intensity evolution. Typhoon Doksuri initially moves northwestward. However, as it nears the northern Philippines, it changes direction and moves towards the west. Approximately 12 hours later, it changes direction again, resuming its northwestward movement. This study applies a diagnostic of potential vorticity (PV) tendency budget to explain the dynamic mechanism of this track deflection meticulously. The results highlight the primary role of the horizontal advection of PV tendency in driving westward motion. For typhoon intensity, Doksuri undergoes rapid intensification (RI) from 0-24 h with an intensification rate of 25.5 m s-1. After that, it continues to intensify by 48 h and thus has a spinup of 40 m s-1 from 0-48 h. Examining the intensification process from 0-48 h reveals that the increasing percentage of convective cloud indicates the formation of deep convection in the inner core, resulting in strong diabatic heating, which enhances the heating efficiency and supports stronger intensity. In addition, the extended Sawyer–Eliassen (SE) equation is used to determine the primary factors contributing to typhoon intensification. The results indicate that the role of diabatic heating in producing intense secondary circulation is significant. The total momentum source contributes less to the secondary circulation than the total heat source, but its contribution to the boundary layer inflow through turbulent friction is also comparable or even more significant in enhancing the transverse circulation near the surface.
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] Department of Earth Sciences

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