浙江大学李小凡团队报道了与热带气旋“Khanun”（2017）的路径方向变化相关的非对称环流旋转。2024年12月12日，国际知名学术期刊《大气科学进展》发表了这一成果。

研究人员通过分析中尺度WRF模式模拟的数据，研究了热带气旋Khanun（2017）移动的动力过程。模拟的运动是由环境风（V_e）和非对称旋转风（V_ψa）的通风气流引起的，这两种风的平均范围是从Khanun中心起半径为200km的区域。结果表明，在Khanun运动增强期间，V_e几乎没有变化，而当Khanun运动由西南向西北转变为西北向运动时，V_e的速度和方向发生了显著变化。

流函数分析表明，移动方向的变化与v_ψ横过Khanun中心的通风流动相一致，并伴有不对称环流旋转。气旋环流中心在快速增强期前和快速增强期间呈逆时针方向旋转，由东北向北移动，并表现出徘徊行为。研究采用基于不对称旋转动能（K_ψa）收支的公式，定量估计了不对称环流的旋转速率。

结果显示，快速的逆时针旋转是由环境动能（K_e）向环境切向流水平平流相关的K_ψa的转换引起的。当耗散项显著时，非对称环流的旋转表现出徘徊行为。耗散项加上与环境径向风引起的对称切向风平流相关的，对称旋转动能（K_ψs）到K_ψa的转换，导致非对称气旋中心向北缓慢顺时针旋转。

附：英文原文

Title: The rotation of asymmetric circulation associated with the track direction change of Tropical Cyclone Khanun (2017)

Author: Yi Shi, Xiaofan Li

Issue&Volume: 2024-12-12

Abstract: The dynamic processes responsible for the movement of tropical cyclone Khanun (2017) were studied by analyzing data from the mesoscale WRF model simulation. The simulated motion was induced by the ventilation flow of both environmental (V_e) and asymmetric rotational (V_ψa) wind averaged over an area with a radius of 200 km from Khanun’s center. The results revealed that during Khanun’s intensification period, V_e barely changed, whereas the speed and direction of V_ψa exhibited significant changes as Khanun’s southwestward movement switched to northwestward movement. The streamfunction analysis revealed that the moving direction change was consistent with the ventilation flow of V_ψa across Khanun’s center associated with asymmetric circulation rotation. The cyclonic circulation center rotated counterclockwise, moving from the northeast to the north before and during the rapid intensification period, and exhibited wandering behavior during this period. The rotation rate of asymmetric circulation was quantitatively estimated using the formulation based on the budget of asymmetric rotational kinetic energy (K_ψa). The calculation revealed that the rapid counterclockwise rotation resulted from the conversion of environmental kinetic energy (K_e) to K_ψa related to the horizontal advection of the environmental tangential flow. The rotation of asymmetric circulation displayed wandering behavior when the dissipation term became significant. The dissipation term plus the conversion from symmetric rotational kinetic energy (K_ψs) to K_ψa associated with the advection of symmetric tangential wind by environmental radial wind led to a slow clockwise rotation of the asymmetric cyclonic center to the north.

DOI: 10.1007/s00376-024-4197-4

Source: http://www.iapjournals.ac.cn/aas/en/article/doi/10.1007/s00376-024-4197-4viewType=HTML