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- Title
The Double Warm-Core Structure of Typhoon Lan (2017) as Observed through the First Japanese Eyewall-Penetrating Aircraft Reconnaissance.
- Authors
Hiroyuki YAMADA; Kosuke ITO; Kazuhisa TSUBOKI; Taro SHINODA; Tadayasu OHIGASHI; Munehiko YAMAGUCHI; Tetsuo NAKAZAWA; Norio NAGAHAMA; Kensaku SHIMIZU
- Abstract
Upper-tropospheric aircraft reconnaissance was carried out for Typhoon Lan (2017) using a civil jet with a newly developed dropsonde system. This was the first time a Japanese research group observed the inner core of an intense typhoon using dropsondes. This paper describes the warm-core structure in the eye and the associated thermodynamic and kinematic features of the eyewall. During two days of reconnaissance, the typhoon preserved its peak intensity in an environment with strengthening vertical shear. The dropsondes captured a double warm-core structure with a higher perturbation temperature in the middle and upper troposphere, which persisted between the two missions. The two warm cores showed a difference in equivalent potential temperature (θ e) of more than 10 K, suggesting different air origins. Saturation-point analysis suggests that the air observed in the upper warm core was entrained from the eyewall. The eyewall updraft in the left-of-shear semicircle had a two-layer structure with a higher θ e and lower absolute angular momentum on the inner side of the updraft core. Analyses of the saturation point and parcel method suggest that the warmer air with a θ e exceeding 370 K on the inner side of the updrafts originated from the eye boundary layer and was eventually transported into the upper warm core. These results led us to hypothesize that the vertical transport of high-θ e air from the eye boundary layer contributed to the continuous eye warming in the upper troposphere against the negative effect of strengthening environmental wind shear on storm intensity. This study demonstrates the significance of eyewallpenetrating upper-tropospheric reconnaissance for monitoring the warm-core structure in the present situation, where accurate measurements of both humidity and temperature for calculating θ e can only be made with dropsonde-type expendables.
- Subjects
RECONNAISSANCE aircraft; WINDSTORMS; WIND shear; BOUNDARY layer (Aerodynamics); VERTICAL drafts (Meteorology); TYPHOONS; TROPICAL cyclones; ELECTRIC bicycles
- Publication
Journal of the Meteorological Society of Japan, 2021, Vol 99, Issue 5, p1297
- ISSN
0026-1165
- Publication type
Article
- DOI
10.2151/jmsj.2021-063