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.
Highlights
As one of the most destructive natural disasters, tropical cyclones (TCs) can cause serious property losses and casualties in TC-prone areas, mostly through destructive winds, storm surges, and severe floods [1]
Continuous efforts have been made during the last few decades based on ever developing instruments and technologies, including ground-based masts [2,3,4], portable meteorological masts [5,6], Doppler radars [7,8], aircrafts [9,10], wind profilers [11], satellite observation [12,13,14], and GPS dropsonde [15,16,17,18,19]
The results describe the evaluations during the period of 04:30–19:30 UTC on 9 August when Lekima moved close to the southeast coast of China and made landfall there
Summary
As one of the most destructive natural disasters, tropical cyclones (TCs) can cause serious property losses and casualties in TC-prone areas, mostly through destructive winds, storm surges, and severe floods [1]. Great advancements of TC knowledge have been achieved, e.g., detailed features of warm-cores, concentric eyewall structures, and correlations between evolution and TC strength, the low-level-jet characteristics of TC wind profiles, and the characteristics and mechanisms of air–sea interactions Among these instruments, the radiosonde balloon is sometimes of special concern because it possesses the following two merits. The southeast coast of China is located at a place where TCs frequently land This region is the most developed economic area of the nation, and it features a high population density and large-scale civil structures that are considerably sensitive to TC wind. The typhoon gradually weakened in the following two days as it moved across the East China Sea. Lekima made landfall over the coast of Zhejiang at 18:00 UTC (local time +08:00) on 9 August, with the central pressure and maximum sustained wind speed equal to 930 hPa and 52.0 m·s−1, respectively. Becausedtehteaielsn.sBemecbalues‐emtehaenepnrsoefmilebslea-tmHeaongpjiraofistlaetsioant Haroenggejinaesrtaatteidonoanrtehgeebnaesriasted on the basis of long-term radiosonde samplings, they are able to smooth out various local features of atmosphere and retain the basic features of large-scale background environments
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