Impact Propagation of Radiosonde Data Assimilation over the Kuroshio and Kuroshio Extension: Case Study on the Early Summer (Baiu) in 2012

• KAWAI Yoshimi

  Research and Development Center for Global Change, Japan Agency for Marine–Earth Science and Technology, Yokosuka, Japan

• MOTEKI Qoosaku

  Department of Coupled Ocean-Atmosphere-Land Processes Research, Japan Agency for Marine–Earth Science and Technology, Yokosuka, Japan

• KUWANO-YOSHIDA Akira

  Application Laboratory, Japan Agency for Marine–Earth Science and Technology, Yokohama, Japan

• ENOMOTO Takeshi

  Application Laboratory, Japan Agency for Marine–Earth Science and Technology, Yokohama, Japan Disaster Prevention Research Institute, Kyoto University, Uji, Japan

• MANDA Atsuyoshi

  Graduate School of Bioresources, Mie University, Tsu, Japan

• NAKAMURA Hisashi

  Application Laboratory, Japan Agency for Marine–Earth Science and Technology, Yokohama, Japan Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan

Abstract

 The present study investigated how impacts of the inclusion of radiosonde observations conducted locally in the early summer of 2012 over the Kuroshio and Kuroshio Extension (KE) can spread over time across the North Pacific basin to influence the predictability of synoptic and large-scale tropospheric circulation. For that purpose, observing system experiments (OSEs) were performed where each of two extra sets of radiosonde data, one obtained over the East China Sea in mid-May and the other over the KE in early July, was added to an atmospheric ensemble data assimilation system for comparison with the corresponding analyses without those data. The experiments show that the impact of the extra data assimilated propagates eastward mainly due to advection by the subtropical jet (STJ) in May and July. The strong STJ in May allows the upper-tropospheric impact to travel across the basin only within two days. Under the weaker STJ, the corresponding impact in July tends to remain within the western Pacific, until it eventually reaches the eastern portion of the basin. Assimilation of the extra radiosonde data over the Kuroshio or KE can lead to a decrease of pressure over the Gulf of Alaska in both May and July.  Additional forecast experiments based on the OSEs for May revealed that the pressure decrease over the Gulf of Alaska can be traced back to the west of the Alaska Peninsula and to the east of Japan over three days. The impacts that originate on different dates via different paths merge over the central North Pacific, reinforcing the cyclone over the Gulf of Alaska. This study presents examples where the impacts of atmospheric observations over the western boundary current can propagate across the ocean basin through the westerlies to influence the forecast skill in distant regions.

Journal

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

  Journal of the Meteorological Society of Japan. Ser. II 95 (2), 71-90, 2017

  Meteorological Society of Japan

Keywords

• data assimilation
• radiosonde
• Kuroshio
• North Pacific
• observing system experiment

Details

• CRID: 1390282681480912768
• NII Article ID: 130005450161
• NII Book ID: AA00702524
• DOI: 10.2151/jmsj.2017-004
• ISSN: 21869057
• ISSN: 00261165
• NDL BIB ID: 028137244
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I028137244
• Web Site: https://www.jstage.jst.go.jp/article/jmsj/95/2/95_2017-004/_pdf
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed