Thermodynamic and Kinematic Structures in the Rainband Region of Typhoon Lekima (2019) at Landfall

Abstract

Super Typhoon Lekima (2019) was the third strongest tropical cyclone (TC) that has ever made landfall in Jiangsu and Zhejiang Provinces, China. During its passage, the storm resulted in catastrophic disasters to mainland China, which made it one of the costliest typhoons in Chinese history. This article presents an observational study on the thermodynamic and kinematic structures of Typhoon Lekima at landfall, mainly based on measurements from radiosonde balloons that were released at different periods from a coastal site located with a nearest distance of ~200 km to the track of Lekima. Observations from a weather radar are first discussed to demonstrate the horizontal structure of the typhoon, and the concentric eyewall structure of Lekima is highlighted. Then, Lekima’s pressure field is analyzed, and a two-dimensional model is proposed to quantify both the radial and height dependence of the pressure distribution. The subsequent analysis focuses on the warm-core like structure in the rainband region. The maximum perturbation of measured equivalent potential temperature with respect to the one of environment reached 25 K at ~5 km. Some factors contributing to the warm-core like feature are discussed. The authors of this article finally investigate the TC wind field. Low-level jets of vertical wind profile in rainband areas were observed at heights of around 1–3 km. Dramatic wind shears were observed in the range of 15–17 km where the outflow layer existed, while wind became considerably weak at the tropopause.

Keywords

• tropical cyclone
• radiosonde balloon
• pressure field
• warm core
• eyewall replacement