The Double Warm-Core Structure of Typhoon Lan (2017) as Observed through the First Japanese Eyewall-Penetrating Aircraft Reconnaissance

• YAMADA Hiroyuki

  Faculty of Science, University of the Ryukyus, Okinawa, Japan

• ITO Kosuke

  Faculty of Science, University of the Ryukyus, Okinawa, Japan Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan

• TSUBOKI Kazuhisa

  Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan

• SHINODA Taro

  Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan

• OHIGASHI Tadayasu

  National Research Institute for Earth Science and Disaster Resilience, Tsukuba, Japan

• YAMAGUCHI Munehiko

  Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan

• NAKAZAWA Tetsuo

  Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan

• NAGAHAMA Norio

  Meisei Electric Co. Ltd., Gunma, Japan

• SHIMIZU Kensaku

  Meisei Electric Co. Ltd., Gunma, Japan

Bibliographic Information

Other Title

• 日本初のアイウォール貫通型航空機観測により捉えられた2017年台風第21号（ラン）の二重暖気核構造

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.

Journal

• Journal of the Meteorological Society of Japan. Ser. II

  Journal of the Meteorological Society of Japan. Ser. II 99 (5), 1297-1327, 2021

  Meteorological Society of Japan

Keywords

• tropical cyclone
• aircraft reconnaissance
• dropsonde
• warm-core structure

Details

• CRID: 1390008445629464832
• NII Article ID: 130008108994
• NII Book ID: AA00702524
• DOI: 10.2151/jmsj.2021-063
• ISSN: 21869057
• ISSN: 00261165
• NDL BIB ID: 031774363
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I031774363
• Web Site: https://www.jstage.jst.go.jp/article/jmsj/99/5/99_2021-063/_pdf
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed