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2017 年度 実施状況報告書

Developing 2-way feedback nested-domain LETKF data assimilation system and application to high-resolution typhoon analyses and forecasts

研究課題

研究課題/領域番号 17K14396
研究機関国立研究開発法人理化学研究所

研究代表者

Lien GuoYuan  国立研究開発法人理化学研究所, 計算科学研究機構, 特別研究員 (50744257)

研究期間 (年度) 2017-04-01 – 2019-03-31
キーワードデータ同化 / 台風 / 気象学
研究実績の概要

The online nested-domain LETKF has been newly implemented in the SCALE-LETKF system. Combined with the existing online nested-domain function in the SCALE-RM model, the SCALE-LETKF is now capable of running both data assimilation cycles and extended ensemble forecasts with multiple nested domains in an online framework. This new function can greatly save the human effort of conducting nested-domain data assimilation experiments compared to the old offline approach. To reduce the unnecessary disk I/O and thus improve the computational efficiency, both the ensemble model forecasts and the LETKF are conducted using single MPI programs. Currently the LETKF analysis using the online nesting function is identical to that using the offline approach. The 2-way feedback LETKF analysis with multiple nested domains is being developed, which is expected to improve the accuracy of the multiple-domain LETKF analysis.
The data assimilation experiments with the September 2015 Kanto-Tohoku Heavy Rainfall case have been conducted using this new online nesting function. Preliminary results show that, compared with the old offline downscaling experiment in Lien et al. (2017, SOLA), the online nested-domain experiment leads to improved forecast skill, due to further performing LETKF analysis in the inner high-resolution domain and frequent coupling of the two domains in the model forecast steps.
In addition, related typhoon data assimilation studies conducted using the SCALE-LETKF system have been published by Honda (2018a,b, MWR, JGR), which the principal investigator coauthored.

現在までの達成度 (区分)
現在までの達成度 (区分)

2: おおむね順調に進展している

理由

The development work of the online nested-domain function in the SCALE-LETKF has been conducted smoothly. The system has been ready for conducting general online nested-domain data assimilation experiments although without the 2-way feedback analysis, which will be implemented soon. In addition, a typhoon case study has been conducted using the new online nesting function with the SCALE-LETKF, and it shows promising results compared to the previous offline downscaling experiments.

今後の研究の推進方策

Research plan for FY2018:
1. Develop new SCALE-LETKF functions specially for typhoons: a) Complete implementing the 2-way feedback nested-domain LETKF with the SCALE-LETKF system. b) Develop vortex-tracking moving nested domains for model forecasts and the LETKF.
2. Test the typhoon data assimilation with the SCALE-LETKF by case studies: a) With the September 2015 Kanto-Tohoku Heavy Rainfall case, conduct an online nested-domain experiment using the 2-way feedback LETKF scheme, and compare the results with the traditional scheme that performs independent analyses for each domain. b) Choose another case with a more intense typhoon and conduct similar experiments to investigate the benefit of the online nested-domain data assimilation system. c) If the vortex-tracking moving nested domain function can be ready, conduct case study experiments with vortex-tracking moving nested domains to allow using higher model resolution in the innermost domain.

次年度使用額が生じた理由

Travel supports, such as those for the principal investigator to attend conferences in order to present the achievement to the community are needed. The journal publication fee is also included in the usage plan. In addition, a disk storage is planned to be bought to store the research data produced by this project.

  • 研究成果

    (7件)

すべて 2018 2017

すべて 雑誌論文 (2件) (うち国際共著 2件、 査読あり 2件、 オープンアクセス 2件) 学会発表 (5件) (うち国際学会 5件、 招待講演 2件)

  • [雑誌論文] Assimilating all-sky Himawari-8 satellite infrared radiances: A case of Typhoon Soudelor (2015)2018

    • 著者名/発表者名
      Takumi Honda, Takemasa Miyoshi, Guo-Yuan Lien, Seiya Nishizawa, Ryuji Yoshida, Sachiho A. Adachi, Koji Terasaki, Kozo Okamoto, Hirofumi Tomita, and Kotaro Bessho
    • 雑誌名

      Monthly Weather Review

      巻: 146 ページ: 213~229

    • DOI

      10.1175/MWR-D-16-0357.1

    • 査読あり / オープンアクセス / 国際共著
  • [雑誌論文] Assimilation of Himawari-8 all-sky radiances every 10 minutes: Impact on precipitation and flood risk prediction2018

    • 著者名/発表者名
      Takumi Honda, Shunji Kotsuki, Guo-Yuan Lien, Yasumitsu Maejima, Kozo Okamoto, and Takemasa Miyoshi
    • 雑誌名

      Journal of Geophysical Research: Atmospheres

      巻: 123 ページ: 965~976

    • DOI

      10.1002/2017JD027096

    • 査読あり / オープンアクセス / 国際共著
  • [学会発表] Issues regarding maintaining ensemble spreads, balance, and high-resolution information in rapid-update-cycle radar data assimilation with the LETKF2018

    • 著者名/発表者名
      Guo-Yuan Lien, and Takemasa Miyoshi
    • 学会等名
      6th International Symposium on Data Assimilation, Munich, Germany
    • 国際学会
  • [学会発表] 30-second-cycle LETKF assimilation of phased array weather radar data2017

    • 著者名/発表者名
      Guo-Yuan Lien, Takemasa Miyoshi, and Juan Ruiz
    • 学会等名
      JpGU-AGU Joint Meeting 2017, Chiba
    • 国際学会 / 招待講演
  • [学会発表] Implicit thinning and localization of dense observation data in the LETKF: A case of phased array weather radar2017

    • 著者名/発表者名
      Guo-Yuan Lien, and Takemasa Miyoshi
    • 学会等名
      JpGU-AGU Joint Meeting 2017, Chiba
    • 国際学会
  • [学会発表] 30-second-cycle LETKF assimilation of phased array weather radar data2017

    • 著者名/発表者名
      Guo-Yuan Lien, and Takemasa Miyoshi
    • 学会等名
      South China Sea Science Conference 2017, Kaohsiung, Taiwan
    • 国際学会 / 招待講演
  • [学会発表] 30-second-cycle LETKF assimilation of phased array weather radar data2017

    • 著者名/発表者名
      Guo-Yuan Lien, Juan Ruiz, and Takemasa Miyoshi
    • 学会等名
      Seventh International WMO Symposium on Data Assimilation, Florianopolis, Brazil
    • 国際学会

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公開日: 2018-12-17  

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