How do Typhoons increase in size? Outer core spin-up process

Prof. Hironori Fudeyasu

Yokohama National University

邀请人：段晚锁 研究员

2025 年 6 月 11 日 上午 10:30-11:20

3号楼1218会议室

报告摘要

The balanced contribution to the intensification of a tropical cyclone simulated in the three-dimensional, nonhydrostatic, full-physics model TCM4, in particular the spin-up of the outer core circulation, is investigated by solving the Sawyer-Eliassen equation and by computing terms in the azimuthal-mean tangential wind tendency equation. Results demonstrate that the azimuthal-mean secondary circulation and the spin-up of the mid-tropospheric outer core circulation in the simulated tropical cyclone are well captured by balance dynamics. The mid-tropospheric inflow develops in response to diabatic heating in mid-upper tropospheric stratiform (anvil) clouds outside the eyewall in active spiral rainbands and transports absolute angular momentum inward to spin up the outer core circulation. Although the azimuthal-mean diabatic heating rate in the eyewall is the largest, its contribution to radial winds and thus the spin-up of outer core circulation in the mid-troposphere is rather weak. This is because the high inertial stability in the inner core region resists the radial inflow in the mid-troposphere, limiting the inward transport of absolute angular momentum. The result thus suggests that diabatic heating in spiral rainbands is the key to the continued growth of the storm scale circulation.

报告人介绍

Dr. Hironori Fudeyasu is a professor at Yokohama National University and Director of the Typhoon Science and Technology Research Center (TRC). He specializes in tropical cyclone dynamics, including intensity change, rapid intensification, and cyclogenesis. He has published more than 50 peer-reviewed papers in international journals. As the founding director of TRC, he leads a nationwide team of over 50 researchers. Since 2022, he has served as the Program Manager of a national Moonshot R&D project on typhoon control, supported by JST. His awards include the Grand Prize of the Global Environment Awards (2020) and the Science and Technology Award by the Japanese MEXT (2025).