Stationary and Transient Asymmetric Features in Tropical Cyclone Eye with Wavenumber-one Instability: Case Study for Typhoon Haishen (2020) with Atmospheric Motion Vectors from 30-second Imaging

Satoki Tsujino, Takeshi Horinouchi, Taiga Tsukada, Hung-Chi Kuo, Hiroyuki Yamada, and Kazuhisa Tsuboki

Published: 2021
DOI

Abstract

Dynamics of rapid changes of intensity and structure in an eyewall replacement cycle of tropical cyclones remain an open question. To clarify the dynamics of the inner eyewall decaying, a quantitative estimation of inner‐core wind fields based on highly frequent observation images with 2.5‐min temporal resolution in the Himawari‐8 satellite is applied to Typhoon Trami (2018) which had a clear concentric eyewall structure. A high tangential wind of 50 m s-1 is estimated at a radius of 30 km, which is located in the inner edge of the inner eyewall, during an active stage of the inner eyewall. During the decaying stage of the inner eyewall, the estimated tangential wind rapidly decreases to about 20 m s-1 at a radius of 24 km. The satellite‐based tangential winds are validated with dropsondes around the inner core by an aircraft. Vorticity field retrieved by the satellite‐based tangential winds during the decaying stage exhibits a rapid decrease in an outer part of the eye and the inner eyewall, and a slow decrease near the storm center. Examination on an absolute angular momentum coordinate indicates that the rapidly slow‐down rotation in the outer edge of the eye and inner eyewall is faster than a slow‐down rotation explained by surface friction. It suggests that asymmetric eddies transport angular momentum across the moat in the inner eyewall dissipation. This study is the first examination of dynamical contributions of asymmetric eddies to the inner‐eyewall dissipation based on satellite‐estimated tangential winds.

Citation

Tsujino, S., T. Horinouchi, T. Tsukada, H.-C. Kuo, H. Yamada, and K. Tsuboki, 2021: Stationary and Transient Asymmetric Features in Tropical Cyclone Eye with Wavenumber-one Instability: Case Study for Typhoon Haishen (2020) with Atmospheric Motion Vectors from 30-second Imaging. Journal of Geophysical Research: Atmospheres, 126, e2020JD034434. https://doi.org/10.1029/2020JD034434.

Public Data

Zenodo

The data derived in this study, the time series of rotational angular velocities of Typhoon Trami (2018), are available at:
https://doi.org/10.5281/zenodo.3958834

LICENSE

The data complies with Creative Commons Attribution 4.0 International

Public Software

Zenodo

The source codes of barotropic model used in this paper are available at:
https://doi.org/10.5281/zenodo.3959296

LICENSE

The software complies with Creative Commons Attribution 4.0 International