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Estimating the geostrophic velocity obtained by HF radar observations in the upstream area of the Kuroshio

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Abstract

A method to extract geostrophic current in the daily mean HF radar data in the Kuroshio upstream region is established by comparison with geostrophic velocity determined from the along-track altimetry data. The estimated Ekman current in the HF velocity is 1.2% (1.5%) and 48° (38°)-clockwise rotated with respect to the daily mean wind in (outside) the Kuroshio. Furthermore, additional temporal smoothing is found necessary to remove residual ageostrophic currents such as the inertial oscillation. After removal of the ageostrophic components, the HF geostrophic velocity agrees well with that from the altimetry data with rms difference 0.14 (0.12) m/s in (outside) the Kuroshio.

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Authors and Affiliations

  1. Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-Koen, Kasuga, Fukuoka, 816-8580, Japan

    Ryoko Tokeshi

  2. Research Institute for Applied Mechanics, Kyushu University, Kasuga-Koen, Kasuga, Fukuoka, 816-8580, Japan

    Kaoru Ichikawa

  3. Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, 237-0061, Japan

    Kaoru Ichikawa

  4. National Institute of Information and Communications Technology, Onna, Kunigami, Okinawa, 904-0411, Japan

    Satoshi Fujii, Kenji Sato & Shoichiro Kojima

  5. Department of Electrical and Electronics Engineering, Faculty of Engineering, University of Ryukyus, Nishihara, Okinawa, 903-0213, Japan

    Satoshi Fujii

Authors
  1. Ryoko Tokeshi
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  2. Kaoru Ichikawa
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  3. Satoshi Fujii
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  4. Kenji Sato
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  5. Shoichiro Kojima
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Correspondence to Kaoru Ichikawa.

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Tokeshi, R., Ichikawa, K., Fujii, S. et al. Estimating the geostrophic velocity obtained by HF radar observations in the upstream area of the Kuroshio. J Oceanogr 63, 711–720 (2007). https://doi.org/10.1007/s10872-007-0062-1

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  • DOI: https://doi.org/10.1007/s10872-007-0062-1

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